90 lines
2.1 KiB
C
90 lines
2.1 KiB
C
#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "img_png.h"
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#define BUFSIZE 1024
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const unsigned char img_png_signature[] = {0x89, 'P', 'N', 'G', '\r', '\n', 0x1a, '\n'};
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uint32_t char_to_uint32 (unsigned char* input) {
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uint32_t val = (input[0] << 24) + (input[1] << 16) + (input[2] << 8) + input[3];
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return val;
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}
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int read_chunk(FILE *fp) {
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struct img_png_chunk cur_chunk;
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// Read chunk length
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unsigned char len[4];
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if(fread(len, sizeof(*len), 4, fp) < 4) {
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fprintf(stderr, "Couldn\'t read chunk length.\n");
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exit(EXIT_FAILURE);
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}
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cur_chunk.length = char_to_uint32(len);
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printf("Chunk length: %lu\n", (unsigned long) cur_chunk.length);
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// Read chunk type
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if(fread(cur_chunk.chunk_type, sizeof(*cur_chunk.chunk_type), 4, fp) < 4) {
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fprintf(stderr, "Couldn\'t read chunk type.\n");
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exit(EXIT_FAILURE);
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}
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printf("Chunk type: %.*s\n", 4, cur_chunk.chunk_type);
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// Read chunk data
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size_t chunk_size = cur_chunk.length / sizeof(unsigned char);
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printf("Chunk size: %zu\n", chunk_size);
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cur_chunk.chunk_data = malloc(chunk_size);
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if(!cur_chunk.chunk_data) {
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perror("Failed to allocate chunk data!");
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exit(EXIT_FAILURE);
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}
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if(fread(cur_chunk.chunk_data, 1, cur_chunk.length, fp) != cur_chunk.length) {
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if(feof(fp)) {
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fprintf(stderr, "File ended prematurely.\n");
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exit(EXIT_FAILURE);
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}
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fprintf(stderr, "Failed to read chunk data!\n");
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exit(EXIT_FAILURE);
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}
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return feof(fp);
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}
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uint8_t* img_png_decode(FILE *fp) {
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unsigned char magic[8];
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// Check PNG Magic
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if(fread(magic, sizeof(*magic), 8, fp) < 8) {
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fprintf(stderr, "Couldn\'t read PNG magic.");
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exit(EXIT_FAILURE);
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}
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if(memcmp(magic, img_png_signature, 8) != 0) {
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fprintf(stderr, "Invalid PNG magic\n");
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exit(EXIT_FAILURE);
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}
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printf("PNG Magic: %#04x%02x%02x%02x%02x%02x%02x%02x\n", magic[0], magic[1], magic[2],
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magic[3], magic[4], magic[5], magic[6], magic[7]);
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struct img_png_chunk cur_chunk;
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// Read chunk
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while (read_chunk(fp) == 0);
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if(!feof(fp)) {
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perror("fread() failed!");
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exit(EXIT_FAILURE);
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}
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return NULL;
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}
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