68 lines
1.5 KiB
C
68 lines
1.5 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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uint8_t* img_png_decode(FILE *fp) {
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unsigned char buffer[BUFSIZE];
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unsigned char magic[8];
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enum chunk_state {
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LENGTH,
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TYPE,
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DATA,
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CRC
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};
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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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// After the magic number is read, we should hit the length of the chunk first.
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enum chunk_state state = LENGTH;
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struct img_png_chunk cur_chunk;
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while(fread(buffer, sizeof(*buffer), BUFSIZE, fp) > 0){
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// Refine later!!!
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switch (state) {
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case LENGTH: {
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unsigned char length[4];
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for (size_t i = 0; i < 4; i++) {
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length[i] = buffer[i];
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}
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cur_chunk.length = char_to_uint32(length);
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printf("Chunk length: %lu\n", (unsigned long)cur_chunk.length);
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}
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}
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}
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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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