/* * Guillaume Cottenceau (gc at mandrakesoft.com) * * Copyright 2002 Mandrakesoft * * This software may be freely redistributed under the terms of the GNU * public license. * */ #include <unistd.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) { 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 = info_ptr->width; height = info_ptr->height; color_type = info_ptr->color_type; bit_depth = info_ptr->bit_depth; 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(info_ptr->rowbytes); png_read_image(png_ptr, row_pointers); } 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); } void process_file(void) { if (info_ptr->color_type != PNG_COLOR_TYPE_RGBA) abort_("[process_file] color_type of input file must be PNG_COLOR_TYPE_RGBA (is %d)", info_ptr->color_type); for (y=0; y<height; y++) { png_byte* row = row_pointers[y]; for (x=0; x<width; x++) { png_byte* ptr = &(row[x*4]); ptr[3] = 255-ptr[0]; ptr[0] = ptr[1] = ptr[2] = 0; } } } 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]); }