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804 lines
30 KiB
804 lines
30 KiB
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#if 0 /* in case someone actually tries to compile this */ |
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|
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/* example.c - an example of using libpng */ |
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|
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/* This is an example of how to use libpng to read and write PNG files. |
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* The file libpng.txt is much more verbose then this. If you have not |
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* read it, do so first. This was designed to be a starting point of an |
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* implementation. This is not officially part of libpng, is hereby placed |
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* in the public domain, and therefore does not require a copyright notice. |
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* |
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* This file does not currently compile, because it is missing certain |
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* parts, like allocating memory to hold an image. You will have to |
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* supply these parts to get it to compile. For an example of a minimal |
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* working PNG reader/writer, see pngtest.c, included in this distribution; |
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* see also the programs in the contrib directory. |
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*/ |
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#include "png.h" |
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|
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/* The png_jmpbuf() macro, used in error handling, became available in |
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* libpng version 1.0.6. If you want to be able to run your code with older |
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* versions of libpng, you must define the macro yourself (but only if it |
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* is not already defined by libpng!). |
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*/ |
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|
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#ifndef png_jmpbuf |
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# define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf) |
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#endif |
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|
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/* Check to see if a file is a PNG file using png_sig_cmp(). png_sig_cmp() |
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* returns zero if the image is a PNG and nonzero if it isn't a PNG. |
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* |
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* The function check_if_png() shown here, but not used, returns nonzero (true) |
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* if the file can be opened and is a PNG, 0 (false) otherwise. |
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* |
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* If this call is successful, and you are going to keep the file open, |
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* you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once |
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* you have created the png_ptr, so that libpng knows your application |
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* has read that many bytes from the start of the file. Make sure you |
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* don't call png_set_sig_bytes() with more than 8 bytes read or give it |
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* an incorrect number of bytes read, or you will either have read too |
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* many bytes (your fault), or you are telling libpng to read the wrong |
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* number of magic bytes (also your fault). |
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* |
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* Many applications already read the first 2 or 4 bytes from the start |
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* of the image to determine the file type, so it would be easiest just |
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* to pass the bytes to png_sig_cmp() or even skip that if you know |
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* you have a PNG file, and call png_set_sig_bytes(). |
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*/ |
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#define PNG_BYTES_TO_CHECK 4 |
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int check_if_png(char *file_name, FILE **fp) |
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{ |
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char buf[PNG_BYTES_TO_CHECK]; |
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|
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/* Open the prospective PNG file. */ |
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if ((*fp = fopen(file_name, "rb")) == NULL) |
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return 0; |
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|
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/* Read in some of the signature bytes */ |
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if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK) |
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return 0; |
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|
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/* Compare the first PNG_BYTES_TO_CHECK bytes of the signature. |
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Return nonzero (true) if they match */ |
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return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK)); |
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} |
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|
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/* Read a PNG file. You may want to return an error code if the read |
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* fails (depending upon the failure). There are two "prototypes" given |
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* here - one where we are given the filename, and we need to open the |
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* file, and the other where we are given an open file (possibly with |
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* some or all of the magic bytes read - see comments above). |
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*/ |
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#ifdef open_file /* prototype 1 */ |
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void read_png(char *file_name) /* We need to open the file */ |
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{ |
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png_structp png_ptr; |
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png_infop info_ptr; |
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unsigned int sig_read = 0; |
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png_uint_32 width, height; |
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int bit_depth, color_type, interlace_type; |
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FILE *fp; |
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if ((fp = fopen(file_name, "rb")) == NULL) |
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return (ERROR); |
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#else no_open_file /* prototype 2 */ |
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void read_png(FILE *fp, unsigned int sig_read) /* file is already open */ |
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{ |
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png_structp png_ptr; |
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png_infop info_ptr; |
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png_uint_32 width, height; |
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int bit_depth, color_type, interlace_type; |
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#endif no_open_file /* only use one prototype! */ |
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|
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/* Create and initialize the png_struct with the desired error handler |
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* functions. If you want to use the default stderr and longjump method, |
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* you can supply NULL for the last three parameters. We also supply the |
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* the compiler header file version, so that we know if the application |
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* was compiled with a compatible version of the library. REQUIRED |
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*/ |
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png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, |
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png_voidp user_error_ptr, user_error_fn, user_warning_fn); |
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if (png_ptr == NULL) |
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{ |
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fclose(fp); |
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return (ERROR); |
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} |
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|
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/* Allocate/initialize the memory for image information. REQUIRED. */ |
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info_ptr = png_create_info_struct(png_ptr); |
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if (info_ptr == NULL) |
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{ |
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fclose(fp); |
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png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL); |
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return (ERROR); |
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} |
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|
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/* Set error handling if you are using the setjmp/longjmp method (this is |
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* the normal method of doing things with libpng). REQUIRED unless you |
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* set up your own error handlers in the png_create_read_struct() earlier. |
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*/ |
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if (setjmp(png_jmpbuf(png_ptr))) |
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{ |
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/* Free all of the memory associated with the png_ptr and info_ptr */ |
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png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL); |
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fclose(fp); |
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/* If we get here, we had a problem reading the file */ |
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return (ERROR); |
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} |
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/* One of the following I/O initialization methods is REQUIRED */ |
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#ifdef streams /* PNG file I/O method 1 */ |
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/* Set up the input control if you are using standard C streams */ |
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png_init_io(png_ptr, fp); |
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#else no_streams /* PNG file I/O method 2 */ |
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/* If you are using replacement read functions, instead of calling |
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* png_init_io() here you would call: |
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*/ |
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png_set_read_fn(png_ptr, (void *)user_io_ptr, user_read_fn); |
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/* where user_io_ptr is a structure you want available to the callbacks */ |
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#endif no_streams /* Use only one I/O method! */ |
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|
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/* If we have already read some of the signature */ |
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png_set_sig_bytes(png_ptr, sig_read); |
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#ifdef hilevel |
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/* |
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* If you have enough memory to read in the entire image at once, |
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* and you need to specify only transforms that can be controlled |
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* with one of the PNG_TRANSFORM_* bits (this presently excludes |
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* dithering, filling, setting background, and doing gamma |
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* adjustment), then you can read the entire image (including |
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* pixels) into the info structure with this call: |
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*/ |
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png_read_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL); |
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#else |
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/* OK, you're doing it the hard way, with the lower-level functions */ |
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/* The call to png_read_info() gives us all of the information from the |
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* PNG file before the first IDAT (image data chunk). REQUIRED |
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*/ |
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png_read_info(png_ptr, info_ptr); |
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png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, |
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&interlace_type, int_p_NULL, int_p_NULL); |
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/**** Set up the data transformations you want. Note that these are all |
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**** optional. Only call them if you want/need them. Many of the |
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**** transformations only work on specific types of images, and many |
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**** are mutually exclusive. |
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****/ |
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/* tell libpng to strip 16 bit/color files down to 8 bits/color */ |
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png_set_strip_16(png_ptr); |
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|
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/* Strip alpha bytes from the input data without combining with the |
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* background (not recommended). |
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*/ |
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png_set_strip_alpha(png_ptr); |
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|
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/* Extract multiple pixels with bit depths of 1, 2, and 4 from a single |
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* byte into separate bytes (useful for paletted and grayscale images). |
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*/ |
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png_set_packing(png_ptr); |
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|
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/* Change the order of packed pixels to least significant bit first |
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* (not useful if you are using png_set_packing). */ |
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png_set_packswap(png_ptr); |
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/* Expand paletted colors into true RGB triplets */ |
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if (color_type == PNG_COLOR_TYPE_PALETTE) |
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png_set_palette_rgb(png_ptr); |
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/* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */ |
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if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) |
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png_set_gray_1_2_4_to_8(png_ptr); |
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|
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/* Expand paletted or RGB images with transparency to full alpha channels |
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* so the data will be available as RGBA quartets. |
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*/ |
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if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) |
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png_set_tRNS_to_alpha(png_ptr); |
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|
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/* Set the background color to draw transparent and alpha images over. |
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* It is possible to set the red, green, and blue components directly |
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* for paletted images instead of supplying a palette index. Note that |
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* even if the PNG file supplies a background, you are not required to |
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* use it - you should use the (solid) application background if it has one. |
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*/ |
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png_color_16 my_background, *image_background; |
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if (png_get_bKGD(png_ptr, info_ptr, &image_background)) |
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png_set_background(png_ptr, image_background, |
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PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); |
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else |
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png_set_background(png_ptr, &my_background, |
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PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); |
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/* Some suggestions as to how to get a screen gamma value */ |
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/* Note that screen gamma is the display_exponent, which includes |
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* the CRT_exponent and any correction for viewing conditions */ |
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if (/* We have a user-defined screen gamma value */) |
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{ |
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screen_gamma = user-defined screen_gamma; |
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} |
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/* This is one way that applications share the same screen gamma value */ |
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else if ((gamma_str = getenv("SCREEN_GAMMA")) != NULL) |
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{ |
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screen_gamma = atof(gamma_str); |
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} |
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/* If we don't have another value */ |
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else |
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{ |
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screen_gamma = 2.2; /* A good guess for a PC monitors in a dimly |
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lit room */ |
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screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */ |
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} |
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/* Tell libpng to handle the gamma conversion for you. The final call |
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* is a good guess for PC generated images, but it should be configurable |
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* by the user at run time by the user. It is strongly suggested that |
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* your application support gamma correction. |
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*/ |
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int intent; |
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if (png_get_sRGB(png_ptr, info_ptr, &intent)) |
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png_set_gamma(png_ptr, screen_gamma, 0.45455); |
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else |
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{ |
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double image_gamma; |
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if (png_get_gAMA(png_ptr, info_ptr, &image_gamma)) |
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png_set_gamma(png_ptr, screen_gamma, image_gamma); |
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else |
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png_set_gamma(png_ptr, screen_gamma, 0.45455); |
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} |
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/* Dither RGB files down to 8 bit palette or reduce palettes |
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* to the number of colors available on your screen. |
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*/ |
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if (color_type & PNG_COLOR_MASK_COLOR) |
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{ |
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int num_palette; |
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png_colorp palette; |
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/* This reduces the image to the application supplied palette */ |
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if (/* we have our own palette */) |
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{ |
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/* An array of colors to which the image should be dithered */ |
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png_color std_color_cube[MAX_SCREEN_COLORS]; |
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png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS, |
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MAX_SCREEN_COLORS, png_uint_16p_NULL, 0); |
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} |
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/* This reduces the image to the palette supplied in the file */ |
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else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette)) |
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{ |
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png_uint_16p histogram; |
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png_get_hIST(png_ptr, info_ptr, &histogram); |
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png_set_dither(png_ptr, palette, num_palette, |
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max_screen_colors, histogram, 0); |
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} |
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} |
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/* invert monochrome files to have 0 as white and 1 as black */ |
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png_set_invert_mono(png_ptr); |
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/* If you want to shift the pixel values from the range [0,255] or |
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* [0,65535] to the original [0,7] or [0,31], or whatever range the |
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* colors were originally in: |
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*/ |
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if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT)) |
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{ |
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png_color_8p sig_bit; |
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png_get_sBIT(png_ptr, info_ptr, &sig_bit); |
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png_set_shift(png_ptr, sig_bit); |
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} |
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/* flip the RGB pixels to BGR (or RGBA to BGRA) */ |
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if (color_type & PNG_COLOR_MASK_COLOR) |
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png_set_bgr(png_ptr); |
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/* swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */ |
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png_set_swap_alpha(png_ptr); |
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/* swap bytes of 16 bit files to least significant byte first */ |
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png_set_swap(png_ptr); |
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/* Add filler (or alpha) byte (before/after each RGB triplet) */ |
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png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER); |
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/* Turn on interlace handling. REQUIRED if you are not using |
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* png_read_image(). To see how to handle interlacing passes, |
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* see the png_read_row() method below: |
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*/ |
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number_passes = png_set_interlace_handling(png_ptr); |
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|
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/* Optional call to gamma correct and add the background to the palette |
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* and update info structure. REQUIRED if you are expecting libpng to |
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* update the palette for you (ie you selected such a transform above). |
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*/ |
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png_read_update_info(png_ptr, info_ptr); |
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/* Allocate the memory to hold the image using the fields of info_ptr. */ |
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/* The easiest way to read the image: */ |
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png_bytep row_pointers[height]; |
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for (row = 0; row < height; row++) |
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{ |
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row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr, |
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info_ptr)); |
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} |
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/* Now it's time to read the image. One of these methods is REQUIRED */ |
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#ifdef entire /* Read the entire image in one go */ |
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png_read_image(png_ptr, row_pointers); |
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#else no_entire /* Read the image one or more scanlines at a time */ |
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/* The other way to read images - deal with interlacing: */ |
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for (pass = 0; pass < number_passes; pass++) |
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{ |
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#ifdef single /* Read the image a single row at a time */ |
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for (y = 0; y < height; y++) |
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{ |
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png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 1); |
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} |
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|
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#else no_single /* Read the image several rows at a time */ |
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for (y = 0; y < height; y += number_of_rows) |
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{ |
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#ifdef sparkle /* Read the image using the "sparkle" effect. */ |
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png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, |
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number_of_rows); |
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#else no_sparkle /* Read the image using the "rectangle" effect */ |
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png_read_rows(png_ptr, png_bytepp_NULL, &row_pointers[y], |
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number_of_rows); |
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#endif no_sparkle /* use only one of these two methods */ |
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} |
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|
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/* if you want to display the image after every pass, do |
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so here */ |
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#endif no_single /* use only one of these two methods */ |
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} |
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#endif no_entire /* use only one of these two methods */ |
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/* read rest of file, and get additional chunks in info_ptr - REQUIRED */ |
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png_read_end(png_ptr, info_ptr); |
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#endif hilevel |
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/* At this point you have read the entire image */ |
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/* clean up after the read, and free any memory allocated - REQUIRED */ |
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png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL); |
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/* close the file */ |
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fclose(fp); |
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/* that's it */ |
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return (OK); |
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} |
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/* progressively read a file */ |
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int |
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initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr) |
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{ |
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/* Create and initialize the png_struct with the desired error handler |
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* functions. If you want to use the default stderr and longjump method, |
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* you can supply NULL for the last three parameters. We also check that |
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* the library version is compatible in case we are using dynamically |
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* linked libraries. |
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*/ |
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*png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, |
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png_voidp user_error_ptr, user_error_fn, user_warning_fn); |
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if (*png_ptr == NULL) |
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{ |
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*info_ptr = NULL; |
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return (ERROR); |
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} |
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*info_ptr = png_create_info_struct(png_ptr); |
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if (*info_ptr == NULL) |
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{ |
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png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); |
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return (ERROR); |
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} |
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if (setjmp(png_jmpbuf((*png_ptr)))) |
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{ |
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png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); |
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return (ERROR); |
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} |
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/* This one's new. You will need to provide all three |
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* function callbacks, even if you aren't using them all. |
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* If you aren't using all functions, you can specify NULL |
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* parameters. Even when all three functions are NULL, |
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* you need to call png_set_progressive_read_fn(). |
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* These functions shouldn't be dependent on global or |
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* static variables if you are decoding several images |
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* simultaneously. You should store stream specific data |
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* in a separate struct, given as the second parameter, |
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* and retrieve the pointer from inside the callbacks using |
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* the function png_get_progressive_ptr(png_ptr). |
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*/ |
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png_set_progressive_read_fn(*png_ptr, (void *)stream_data, |
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info_callback, row_callback, end_callback); |
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return (OK); |
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} |
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int |
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process_data(png_structp *png_ptr, png_infop *info_ptr, |
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png_bytep buffer, png_uint_32 length) |
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{ |
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if (setjmp(png_jmpbuf((*png_ptr)))) |
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{ |
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/* Free the png_ptr and info_ptr memory on error */ |
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png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL); |
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return (ERROR); |
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} |
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/* This one's new also. Simply give it chunks of data as |
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* they arrive from the data stream (in order, of course). |
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* On Segmented machines, don't give it any more than 64K. |
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* The library seems to run fine with sizes of 4K, although |
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* you can give it much less if necessary (I assume you can |
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* give it chunks of 1 byte, but I haven't tried with less |
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* than 256 bytes yet). When this function returns, you may |
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* want to display any rows that were generated in the row |
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* callback, if you aren't already displaying them there. |
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*/ |
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png_process_data(*png_ptr, *info_ptr, buffer, length); |
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return (OK); |
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} |
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info_callback(png_structp png_ptr, png_infop info) |
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{ |
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/* do any setup here, including setting any of the transformations |
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* mentioned in the Reading PNG files section. For now, you _must_ |
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* call either png_start_read_image() or png_read_update_info() |
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* after all the transformations are set (even if you don't set |
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* any). You may start getting rows before png_process_data() |
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* returns, so this is your last chance to prepare for that. |
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*/ |
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} |
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row_callback(png_structp png_ptr, png_bytep new_row, |
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png_uint_32 row_num, int pass) |
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{ |
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/* |
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* This function is called for every row in the image. If the |
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* image is interlaced, and you turned on the interlace handler, |
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* this function will be called for every row in every pass. |
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* |
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* In this function you will receive a pointer to new row data from |
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* libpng called new_row that is to replace a corresponding row (of |
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* the same data format) in a buffer allocated by your application. |
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* |
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* The new row data pointer new_row may be NULL, indicating there is |
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* no new data to be replaced (in cases of interlace loading). |
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* |
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* If new_row is not NULL then you need to call |
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* png_progressive_combine_row() to replace the corresponding row as |
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* shown below: |
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*/ |
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/* Check if row_num is in bounds. */ |
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if((row_num >= 0) && (row_num < height)) |
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{ |
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/* Get pointer to corresponding row in our |
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* PNG read buffer. |
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*/ |
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png_bytep old_row = ((png_bytep *)our_data)[row_num]; |
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|
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/* If both rows are allocated then copy the new row |
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* data to the corresponding row data. |
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*/ |
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if((old_row != NULL) && (new_row != NULL)) |
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png_progressive_combine_row(png_ptr, old_row, new_row); |
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} |
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/* |
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* The rows and passes are called in order, so you don't really |
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* need the row_num and pass, but I'm supplying them because it |
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* may make your life easier. |
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* |
|
* For the non-NULL rows of interlaced images, you must call |
|
* png_progressive_combine_row() passing in the new row and the |
|
* old row, as demonstrated above. You can call this function for |
|
* NULL rows (it will just return) and for non-interlaced images |
|
* (it just does the png_memcpy for you) if it will make the code |
|
* easier. Thus, you can just do this for all cases: |
|
*/ |
|
|
|
png_progressive_combine_row(png_ptr, old_row, new_row); |
|
|
|
/* where old_row is what was displayed for previous rows. Note |
|
* that the first pass (pass == 0 really) will completely cover |
|
* the old row, so the rows do not have to be initialized. After |
|
* the first pass (and only for interlaced images), you will have |
|
* to pass the current row as new_row, and the function will combine |
|
* the old row and the new row. |
|
*/ |
|
} |
|
|
|
end_callback(png_structp png_ptr, png_infop info) |
|
{ |
|
/* this function is called when the whole image has been read, |
|
* including any chunks after the image (up to and including |
|
* the IEND). You will usually have the same info chunk as you |
|
* had in the header, although some data may have been added |
|
* to the comments and time fields. |
|
* |
|
* Most people won't do much here, perhaps setting a flag that |
|
* marks the image as finished. |
|
*/ |
|
} |
|
|
|
/* write a png file */ |
|
void write_png(char *file_name /* , ... other image information ... */) |
|
{ |
|
FILE *fp; |
|
png_structp png_ptr; |
|
png_infop info_ptr; |
|
png_colorp palette; |
|
|
|
/* open the file */ |
|
fp = fopen(file_name, "wb"); |
|
if (fp == NULL) |
|
return (ERROR); |
|
|
|
/* Create and initialize the png_struct with the desired error handler |
|
* functions. If you want to use the default stderr and longjump method, |
|
* you can supply NULL for the last three parameters. We also check that |
|
* the library version is compatible with the one used at compile time, |
|
* in case we are using dynamically linked libraries. REQUIRED. |
|
*/ |
|
png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, |
|
png_voidp user_error_ptr, user_error_fn, user_warning_fn); |
|
|
|
if (png_ptr == NULL) |
|
{ |
|
fclose(fp); |
|
return (ERROR); |
|
} |
|
|
|
/* Allocate/initialize the image information data. REQUIRED */ |
|
info_ptr = png_create_info_struct(png_ptr); |
|
if (info_ptr == NULL) |
|
{ |
|
fclose(fp); |
|
png_destroy_write_struct(&png_ptr, png_infopp_NULL); |
|
return (ERROR); |
|
} |
|
|
|
/* Set error handling. REQUIRED if you aren't supplying your own |
|
* error handling functions in the png_create_write_struct() call. |
|
*/ |
|
if (setjmp(png_jmpbuf(png_ptr))) |
|
{ |
|
/* If we get here, we had a problem reading the file */ |
|
fclose(fp); |
|
png_destroy_write_struct(&png_ptr, &info_ptr); |
|
return (ERROR); |
|
} |
|
|
|
/* One of the following I/O initialization functions is REQUIRED */ |
|
#ifdef streams /* I/O initialization method 1 */ |
|
/* set up the output control if you are using standard C streams */ |
|
png_init_io(png_ptr, fp); |
|
#else no_streams /* I/O initialization method 2 */ |
|
/* If you are using replacement read functions, instead of calling |
|
* png_init_io() here you would call */ |
|
png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn, |
|
user_IO_flush_function); |
|
/* where user_io_ptr is a structure you want available to the callbacks */ |
|
#endif no_streams /* only use one initialization method */ |
|
|
|
#ifdef hilevel |
|
/* This is the easy way. Use it if you already have all the |
|
* image info living info in the structure. You could "|" many |
|
* PNG_TRANSFORM flags into the png_transforms integer here. |
|
*/ |
|
png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL); |
|
#else |
|
/* This is the hard way */ |
|
|
|
/* Set the image information here. Width and height are up to 2^31, |
|
* bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on |
|
* the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY, |
|
* PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB, |
|
* or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or |
|
* PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST |
|
* currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED |
|
*/ |
|
png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???, |
|
PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE); |
|
|
|
/* set the palette if there is one. REQUIRED for indexed-color images */ |
|
palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH |
|
* sizeof (png_color)); |
|
/* ... set palette colors ... */ |
|
png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH); |
|
/* You must not free palette here, because png_set_PLTE only makes a link to |
|
the palette that you malloced. Wait until you are about to destroy |
|
the png structure. */ |
|
|
|
/* optional significant bit chunk */ |
|
/* if we are dealing with a grayscale image then */ |
|
sig_bit.gray = true_bit_depth; |
|
/* otherwise, if we are dealing with a color image then */ |
|
sig_bit.red = true_red_bit_depth; |
|
sig_bit.green = true_green_bit_depth; |
|
sig_bit.blue = true_blue_bit_depth; |
|
/* if the image has an alpha channel then */ |
|
sig_bit.alpha = true_alpha_bit_depth; |
|
png_set_sBIT(png_ptr, info_ptr, sig_bit); |
|
|
|
|
|
/* Optional gamma chunk is strongly suggested if you have any guess |
|
* as to the correct gamma of the image. |
|
*/ |
|
png_set_gAMA(png_ptr, info_ptr, gamma); |
|
|
|
/* Optionally write comments into the image */ |
|
text_ptr[0].key = "Title"; |
|
text_ptr[0].text = "Mona Lisa"; |
|
text_ptr[0].compression = PNG_TEXT_COMPRESSION_NONE; |
|
text_ptr[1].key = "Author"; |
|
text_ptr[1].text = "Leonardo DaVinci"; |
|
text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE; |
|
text_ptr[2].key = "Description"; |
|
text_ptr[2].text = "<long text>"; |
|
text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt; |
|
#ifdef PNG_iTXt_SUPPORTED |
|
text_ptr[0].lang = NULL; |
|
text_ptr[1].lang = NULL; |
|
text_ptr[2].lang = NULL; |
|
#endif |
|
png_set_text(png_ptr, info_ptr, text_ptr, 3); |
|
|
|
/* other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs, */ |
|
/* note that if sRGB is present the gAMA and cHRM chunks must be ignored |
|
* on read and must be written in accordance with the sRGB profile */ |
|
|
|
/* Write the file header information. REQUIRED */ |
|
png_write_info(png_ptr, info_ptr); |
|
|
|
/* If you want, you can write the info in two steps, in case you need to |
|
* write your private chunk ahead of PLTE: |
|
* |
|
* png_write_info_before_PLTE(write_ptr, write_info_ptr); |
|
* write_my_chunk(); |
|
* png_write_info(png_ptr, info_ptr); |
|
* |
|
* However, given the level of known- and unknown-chunk support in 1.1.0 |
|
* and up, this should no longer be necessary. |
|
*/ |
|
|
|
/* Once we write out the header, the compression type on the text |
|
* chunks gets changed to PNG_TEXT_COMPRESSION_NONE_WR or |
|
* PNG_TEXT_COMPRESSION_zTXt_WR, so it doesn't get written out again |
|
* at the end. |
|
*/ |
|
|
|
/* set up the transformations you want. Note that these are |
|
* all optional. Only call them if you want them. |
|
*/ |
|
|
|
/* invert monochrome pixels */ |
|
png_set_invert_mono(png_ptr); |
|
|
|
/* Shift the pixels up to a legal bit depth and fill in |
|
* as appropriate to correctly scale the image. |
|
*/ |
|
png_set_shift(png_ptr, &sig_bit); |
|
|
|
/* pack pixels into bytes */ |
|
png_set_packing(png_ptr); |
|
|
|
/* swap location of alpha bytes from ARGB to RGBA */ |
|
png_set_swap_alpha(png_ptr); |
|
|
|
/* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into |
|
* RGB (4 channels -> 3 channels). The second parameter is not used. |
|
*/ |
|
png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); |
|
|
|
/* flip BGR pixels to RGB */ |
|
png_set_bgr(png_ptr); |
|
|
|
/* swap bytes of 16-bit files to most significant byte first */ |
|
png_set_swap(png_ptr); |
|
|
|
/* swap bits of 1, 2, 4 bit packed pixel formats */ |
|
png_set_packswap(png_ptr); |
|
|
|
/* turn on interlace handling if you are not using png_write_image() */ |
|
if (interlacing) |
|
number_passes = png_set_interlace_handling(png_ptr); |
|
else |
|
number_passes = 1; |
|
|
|
/* The easiest way to write the image (you may have a different memory |
|
* layout, however, so choose what fits your needs best). You need to |
|
* use the first method if you aren't handling interlacing yourself. |
|
*/ |
|
png_uint_32 k, height, width; |
|
png_byte image[height][width*bytes_per_pixel]; |
|
png_bytep row_pointers[height]; |
|
for (k = 0; k < height; k++) |
|
row_pointers[k] = image + k*width*bytes_per_pixel; |
|
|
|
/* One of the following output methods is REQUIRED */ |
|
#ifdef entire /* write out the entire image data in one call */ |
|
png_write_image(png_ptr, row_pointers); |
|
|
|
/* the other way to write the image - deal with interlacing */ |
|
|
|
#else no_entire /* write out the image data by one or more scanlines */ |
|
/* The number of passes is either 1 for non-interlaced images, |
|
* or 7 for interlaced images. |
|
*/ |
|
for (pass = 0; pass < number_passes; pass++) |
|
{ |
|
/* Write a few rows at a time. */ |
|
png_write_rows(png_ptr, &row_pointers[first_row], number_of_rows); |
|
|
|
/* If you are only writing one row at a time, this works */ |
|
for (y = 0; y < height; y++) |
|
{ |
|
png_write_rows(png_ptr, &row_pointers[y], 1); |
|
} |
|
} |
|
#endif no_entire /* use only one output method */ |
|
|
|
/* You can write optional chunks like tEXt, zTXt, and tIME at the end |
|
* as well. Shouldn't be necessary in 1.1.0 and up as all the public |
|
* chunks are supported and you can use png_set_unknown_chunks() to |
|
* register unknown chunks into the info structure to be written out. |
|
*/ |
|
|
|
/* It is REQUIRED to call this to finish writing the rest of the file */ |
|
png_write_end(png_ptr, info_ptr); |
|
#endif hilevel |
|
|
|
/* If you png_malloced a palette, free it here (don't free info_ptr->palette, |
|
as recommended in versions 1.0.5m and earlier of this example; if |
|
libpng mallocs info_ptr->palette, libpng will free it). If you |
|
allocated it with malloc() instead of png_malloc(), use free() instead |
|
of png_free(). */ |
|
png_free(png_ptr, palette); |
|
palette=NULL; |
|
|
|
/* Similarly, if you png_malloced any data that you passed in with |
|
png_set_something(), such as a hist or trans array, free it here, |
|
when you can be sure that libpng is through with it. */ |
|
png_free(png_ptr, trans); |
|
trans=NULL; |
|
|
|
/* clean up after the write, and free any memory allocated */ |
|
png_destroy_write_struct(&png_ptr, &info_ptr); |
|
|
|
/* close the file */ |
|
fclose(fp); |
|
|
|
/* that's it */ |
|
return (OK); |
|
} |
|
|
|
#endif /* if 0 */
|
|
|