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/*
* Copyright 2002-2010 Guillaume Cottenceau.
*
* This software may be freely redistributed under the terms
* of the X11 license.
*/
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#define PNG_DEBUG 3
#include <png.h>
void abort_(const char * s, ...)
{
va_list args;
va_start(args, s);
vfprintf(stderr, s, args);
fprintf(stderr, "\n");
va_end(args);
abort();
}
int x, y;
int width, height;
png_byte color_type;
png_byte bit_depth;
png_structp png_ptr;
png_infop info_ptr;
int number_of_passes;
png_bytep * row_pointers;
void read_png_file(char* file_name)
{
unsigned char header[8]; // 8 is the maximum size that can be checked
/* open file and test for it being a png */
FILE *fp = fopen(file_name, "rb");
if (!fp)
abort_("[read_png_file] File %s could not be opened for reading", file_name);
fread(header, 1, 8, fp);
if (png_sig_cmp(header, 0, 8))
abort_("[read_png_file] File %s is not recognized as a PNG file", file_name);
/* initialize stuff */
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!png_ptr)
abort_("[read_png_file] png_create_read_struct failed");
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
abort_("[read_png_file] png_create_info_struct failed");
if (setjmp(png_jmpbuf(png_ptr)))
abort_("[read_png_file] Error during init_io");
png_init_io(png_ptr, fp);
png_set_sig_bytes(png_ptr, 8);
png_read_info(png_ptr, info_ptr);
width = png_get_image_width(png_ptr, info_ptr);
height = png_get_image_height(png_ptr, info_ptr);
color_type = png_get_color_type(png_ptr, info_ptr);
bit_depth = png_get_bit_depth(png_ptr, info_ptr);
number_of_passes = png_set_interlace_handling(png_ptr);
png_read_update_info(png_ptr, info_ptr);
/* read file */
if (setjmp(png_jmpbuf(png_ptr)))
abort_("[read_png_file] Error during read_image");
row_pointers = (png_bytep*) malloc(sizeof(png_bytep) * height);
for (y=0; y<height; y++)
row_pointers[y] = (png_byte*) malloc(png_get_rowbytes(png_ptr,info_ptr));
png_read_image(png_ptr, row_pointers);
fclose(fp);
}
void write_png_file(char* file_name)
{
/* create file */
FILE *fp = fopen(file_name, "wb");
if (!fp)
abort_("[write_png_file] File %s could not be opened for writing", file_name);
/* initialize stuff */
png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!png_ptr)
abort_("[write_png_file] png_create_write_struct failed");
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
abort_("[write_png_file] png_create_info_struct failed");
if (setjmp(png_jmpbuf(png_ptr)))
abort_("[write_png_file] Error during init_io");
png_init_io(png_ptr, fp);
/* write header */
if (setjmp(png_jmpbuf(png_ptr)))
abort_("[write_png_file] Error during writing header");
png_set_IHDR(png_ptr, info_ptr, width, height,
bit_depth, color_type, PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
png_write_info(png_ptr, info_ptr);
/* write bytes */
if (setjmp(png_jmpbuf(png_ptr)))
abort_("[write_png_file] Error during writing bytes");
png_write_image(png_ptr, row_pointers);
/* end write */
if (setjmp(png_jmpbuf(png_ptr)))
abort_("[write_png_file] Error during end of write");
png_write_end(png_ptr, NULL);
/* cleanup heap allocation */
for (y=0; y<height; y++)
free(row_pointers[y]);
free(row_pointers);
fclose(fp);
}
void process_file(void)
{
if (png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_RGB)
{
abort_("[process_file] input file is PNG_COLOR_TYPE_RGB but must be "
"PNG_COLOR_TYPE_RGBA (lacks the alpha channel)");
}
if (png_get_color_type(png_ptr, info_ptr) != PNG_COLOR_TYPE_RGBA)
{
abort_("[process_file] color_type of input file must be "
"PNG_COLOR_TYPE_RGBA (%d) (is %d)",
PNG_COLOR_TYPE_RGBA, png_get_color_type(png_ptr, info_ptr));
}
for (y=0; y<height; y++)
{
png_byte* row = row_pointers[y];
for (x=0; x<width; x++)
{
png_byte* ptr = &(row[x*4]);
printf("Pixel at position [ %d - %d ] has RGBA values: %d - %d - %d - %d\n",
x, y, ptr[0], ptr[1], ptr[2], ptr[3]);
}
}
}
int main(int argc, char **argv)
{
if (argc != 3)
abort_("Usage: program_name <file_in> <file_out>");
read_png_file(argv[1]);
process_file();
write_png_file(argv[2]);
return 0;
}
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