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gifanalyzer: decode Graphic Control Extension

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This commit is contained in:
Thomas Bernard 2018-01-30 15:05:23 +01:00
parent 0f780f1e3f
commit 6bfb34fd19
1 changed files with 72 additions and 13 deletions
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85
tools/gifanalyzer/gifanalyzer.c
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@ -26,11 +26,12 @@
static void read_image(FILE * theFile);
static void read_palette(FILE * theFile, int count);
static void read_extension(FILE * theFile);
int main(int argc, char* argv[])
{
FILE* theFile;
uint8_t buffer[256];
uint8_t buffer[8];
uint16_t w,h;
if(argc < 2)
@ -78,19 +79,27 @@ int main(int argc, char* argv[])
printf("Color palette:\n");
read_palette(theFile, color_table_size);
int i = 0;
do {
fread(buffer,1,1,theFile);
printf("%02X ", buffer[0]);
i++;
} while (buffer[0] != ',');
printf("\n");
if (i > 1)
printf("Skipped %d meaningless bytes before image descriptor\n",i);
read_image(theFile);
while (fread(buffer,1,1,theFile) == 1)
{
if (buffer[0] == ';') // 0x3B
{
printf("0x3B GIF Trailer Byte\n");
break;
}
else switch (buffer[0])
{
case '!': // 0x21
read_extension(theFile);
break;
case ',': // 0x2C
read_image(theFile);
break;
default:
printf("%02X ", buffer[0]);
}
}
printf("offset : %lu\n", ftell(theFile));
fclose(theFile);
}
@ -119,6 +128,9 @@ static void read_image(FILE * theFile)
if (buffer[0]&0x80)
read_palette(theFile, color_table_size);
fread(buffer,1,1,theFile);
printf("\tLZW Minimum Code Size : %d\n", buffer[0]);
while (!feof(theFile))
{
fread(buffer,1,1,theFile);
@ -144,3 +156,50 @@ static void read_palette(FILE * theFile, int count)
if ((i+1)%8 ==0)puts("");
}
}
static void read_extension(FILE * theFile)
{
uint8_t extension_id;
uint8_t buffer[256];
int block_index = 0;
int i;
fread(&extension_id,1,1,theFile);
printf("extension 0x%02X ", extension_id);
switch (extension_id)
{
case 0xF9:
printf("Graphic Control Extension :");
break;
default:
break;
}
putchar('\n');
while (fread(buffer,1,1,theFile) == 1) // Block size
{
if (buffer[0] == 0)
break;
fread(buffer+1,1,buffer[0],theFile);
switch (extension_id)
{
case 0xF9:
if (block_index == 0)
{
printf("\tDisposal method=%d, User Input Flag=%d, Transparent Color Flag=%d (Index %d=0x%02X)\n",
(buffer[1] & 0x1C) >> 2, (buffer[1] & 0x02) >> 1, (buffer[1] & 0x01),
buffer[4], buffer[4]);
printf("\tDelay Time : %lums\n", (((unsigned long)buffer[3] << 8) | buffer[2]) * 10);
}
break;
default:
printf("#%02d %3dbytes ", block_index, buffer[0]);
for (i = 1; i <= buffer[0]; i++)
printf("%02X ", buffer[i]);
printf("| ");
for (i = 1; i <= buffer[0]; i++)
putchar((buffer[i] >= ' ' && buffer[i] < 128)?buffer[i]:'.');
putchar('\n');
}
block_index++;
}
}