PNGファイルの構造をざざっと見る

xpng

#include <stdio.h>
#include <ctype.h>

typedef unsigned char BYTE;
typedef int INT4;

int main()
{
    BYTE pngHdr[8];
    BYTE buf4[4];
    int addr = 0;
    int i;

    fread(pngHdr, 8, 1, stdin);
    printf("PNG HDR: ");
    for (i = 0; i < 8; i++) {
        printf("%02x ", pngHdr[i]);
    }
    printf("\n");
    addr += 8;

    while (fread(buf4, 4, 1, stdin)) {
        INT4 chunkSize = 0;
        for (i = 0; i < 4; i++) {
            chunkSize |= buf4[i] << ((3 - i) * 8);
        }
        printf("%08o chunkSize = %d\n", addr, chunkSize);
        addr += 4;

        fread(buf4, 4, 1, stdin);
        printf("chunk ");
        for (i = 0; i < 4; i++) {
            printf("[%c]", buf4[i]);
        }
        printf("\n");
        addr += 4;

        for (i = 0; i < chunkSize; i++) {
            int c = getchar();
            /*
            printf("%02x", c);
            if (isprint(c)) {
                printf("(%c)", c);
            }
            printf(" ");
            */
            printf("%c", isprint(c) ? c : '.');
        }
        printf("\n");
        addr += chunkSize;

        fread(buf4, 4, 1, stdin);
      	printf("crc: ");
	      for (i = 0; i < 4; i++) {
            printf("%02x ", buf4[i]);
	      }
	      printf("\n");
        addr += 4;
    }
    return 0;
}