863 lines
31 KiB
C
863 lines
31 KiB
C
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#if 0 /* in case someone actually tries to compile this */
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/* example.c - an example of using libpng
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* Last changed in libpng 1.5.7 [December 15, 2011]
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* Maintained 1998-2011 Glenn Randers-Pehrson
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* Maintained 1996, 1997 Andreas Dilger
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* Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
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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-manual.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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* To the extent possible under law, the authors have waived all copyright and
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* related or neighboring rights to this file.
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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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#define _POSIX_SOURCE 1 /* libpng and zlib are POSIX-compliant. You may
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* change this if your application uses non-POSIX
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* extensions. */
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#include "png.h"
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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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#ifndef png_jmpbuf
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# define png_jmpbuf(png_ptr) ((png_ptr)->png_jmpbuf)
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#endif
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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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/* 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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/* 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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/* 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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/* 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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/* 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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/* 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, NULL, NULL);
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return (ERROR);
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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, 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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/* 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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* quantizing, 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, 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, NULL, 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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* Use accurate scaling if it's available, otherwise just chop off the
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* low byte.
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*/
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#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
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png_set_scale_16(png_ptr);
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#else
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png_set_strip_16(png_ptr);
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#endif
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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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/* 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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/* 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_to_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_expand_gray_1_2_4_to_8(png_ptr);
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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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/* 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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*
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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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*/
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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 monitor 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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#ifdef PNG_READ_QUANTIZE_SUPPORTED
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/* Quantize 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 quantized */
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png_color std_color_cube[MAX_SCREEN_COLORS];
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png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
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MAX_SCREEN_COLORS, 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 = NULL;
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png_get_hIST(png_ptr, info_ptr, &histogram);
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png_set_quantize(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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#endif /* PNG_READ_QUANTIZE_SUPPORTED */
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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_p;
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png_get_sBIT(png_ptr, info_ptr, &sig_bit_p);
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png_set_shift(png_ptr, sig_bit_p);
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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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#ifdef PNG_READ_INTERLACING_SUPPORTED
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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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#else
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number_passes = 1;
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#endif /* PNG_READ_INTERLACING_SUPPORTED */
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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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/* Clear the pointer array */
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for (row = 0; row < height; row++)
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row_pointers[row] = NULL;
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for (row = 0; row < height; row++)
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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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/* 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], NULL, 1);
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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], 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, 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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/* If you want to display the image after every pass, do 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, 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, 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, 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,
|
|
png_bytep buffer, png_uint_32 length)
|
|
{
|
|
if (setjmp(png_jmpbuf((*png_ptr))))
|
|
{
|
|
/* Free the png_ptr and info_ptr memory on error */
|
|
png_destroy_read_struct(png_ptr, info_ptr, NULL);
|
|
return (ERROR);
|
|
}
|
|
|
|
/* This one's new also. Simply give it chunks of data as
|
|
* they arrive from the data stream (in order, of course).
|
|
* On segmented machines, don't give it any more than 64K.
|
|
* The library seems to run fine with sizes of 4K, although
|
|
* you can give it much less if necessary (I assume you can
|
|
* give it chunks of 1 byte, but I haven't tried with less
|
|
* than 256 bytes yet). When this function returns, you may
|
|
* want to display any rows that were generated in the row
|
|
* callback, if you aren't already displaying them there.
|
|
*/
|
|
png_process_data(*png_ptr, *info_ptr, buffer, length);
|
|
return (OK);
|
|
}
|
|
|
|
info_callback(png_structp png_ptr, png_infop info)
|
|
{
|
|
/* Do any setup here, including setting any of the transformations
|
|
* mentioned in the Reading PNG files section. For now, you _must_
|
|
* call either png_start_read_image() or png_read_update_info()
|
|
* after all the transformations are set (even if you don't set
|
|
* any). You may start getting rows before png_process_data()
|
|
* returns, so this is your last chance to prepare for that.
|
|
*/
|
|
}
|
|
|
|
row_callback(png_structp png_ptr, png_bytep new_row,
|
|
png_uint_32 row_num, int pass)
|
|
{
|
|
/*
|
|
* This function is called for every row in the image. If the
|
|
* image is interlaced, and you turned on the interlace handler,
|
|
* this function will be called for every row in every pass.
|
|
*
|
|
* In this function you will receive a pointer to new row data from
|
|
* libpng called new_row that is to replace a corresponding row (of
|
|
* the same data format) in a buffer allocated by your application.
|
|
*
|
|
* The new row data pointer "new_row" may be NULL, indicating there is
|
|
* no new data to be replaced (in cases of interlace loading).
|
|
*
|
|
* If new_row is not NULL then you need to call
|
|
* png_progressive_combine_row() to replace the corresponding row as
|
|
* shown below:
|
|
*/
|
|
|
|
/* Get pointer to corresponding row in our
|
|
* PNG read buffer.
|
|
*/
|
|
png_bytep old_row = ((png_bytep *)our_data)[row_num];
|
|
|
|
#ifdef PNG_READ_INTERLACING_SUPPORTED
|
|
/* If both rows are allocated then copy the new row
|
|
* data to the corresponding row data.
|
|
*/
|
|
if ((old_row != NULL) && (new_row != NULL))
|
|
png_progressive_combine_row(png_ptr, old_row, new_row);
|
|
|
|
/*
|
|
* The rows and passes are called in order, so you don't really
|
|
* need the row_num and pass, but I'm supplying them because it
|
|
* may make your life easier.
|
|
*
|
|
* 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.
|
|
*/
|
|
#endif /* PNG_READ_INTERLACING_SUPPORTED */
|
|
}
|
|
|
|
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, 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 writing 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 write 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 in the structure. You could "|" many
|
|
* PNG_TRANSFORM flags into the png_transforms integer here.
|
|
*/
|
|
png_write_png(png_ptr, info_ptr, png_transforms, 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
|
|
* png_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 (sBIT) chunk */
|
|
png_color_8 sig_bit;
|
|
|
|
/* 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[0].itxt_length = 0;
|
|
text_ptr[0].lang = NULL;
|
|
text_ptr[0].lang_key = NULL;
|
|
text_ptr[1].key = "Author";
|
|
text_ptr[1].text = "Leonardo DaVinci";
|
|
text_ptr[1].compression = PNG_TEXT_COMPRESSION_NONE;
|
|
text_ptr[1].itxt_length = 0;
|
|
text_ptr[1].lang = NULL;
|
|
text_ptr[1].lang_key = NULL;
|
|
text_ptr[2].key = "Description";
|
|
text_ptr[2].text = "<long text>";
|
|
text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
|
|
text_ptr[2].itxt_length = 0;
|
|
text_ptr[2].lang = NULL;
|
|
text_ptr[2].lang_key = NULL;
|
|
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, if your application chooses to write them, they 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 1.2.0
|
|
* 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];
|
|
|
|
if (height > PNG_UINT_32_MAX/png_sizeof(png_bytep))
|
|
png_error (png_ptr, "Image is too tall to process in memory");
|
|
|
|
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 1.2.0 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;
|
|
/* Whenever you use png_free() it is a good idea to set the pointer to
|
|
* NULL in case your application inadvertently tries to png_free() it
|
|
* again. When png_free() sees a NULL it returns without action, thus
|
|
* avoiding the double-free security problem.
|
|
*/
|
|
|
|
/* 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 */
|