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stb_image: Tweak end-of-JPEG junk scanning loop. 

Be a bit more picky about what we consider a valid marker.
0xff 0x00 (stuffed 0 byte) should not count.

Fixes issue #1409.
This commit is contained in:
Fabian Giesen 2023-01-22 19:42:55 -08:00
parent 1096389590
commit 0613e9c043
1 changed files with 23 additions and 8 deletions
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31
stb_image.h
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@ -3383,6 +3383,28 @@ static int stbi__decode_jpeg_header(stbi__jpeg *z, int scan)
return 1;
}
static int stbi__skip_jpeg_junk_at_end(stbi__jpeg *j)
{
// some JPEGs have junk at end, skip over it but if we find what looks
// like a valid marker, resume there
while (!stbi__at_eof(j->s)) {
int x = stbi__get8(j->s);
while (x == 255) { // might be a marker
if (stbi__at_eof(j->s)) return STBI__MARKER_none;
x = stbi__get8(j->s);
if (x != 0x00 && x != 0xff) {
// not a stuffed zero or lead-in to another marker, looks
// like an actual marker, return it
return x;
}
// stuffed zero has x=0 now which ends the loop, meaning we go
// back to regular scan loop.
// repeated 0xff keeps trying to read the next byte of the marker.
}
}
return STBI__MARKER_none;
}
// decode image to YCbCr format
static int stbi__decode_jpeg_image(stbi__jpeg *j)
{
@ -3399,14 +3421,7 @@ static int stbi__decode_jpeg_image(stbi__jpeg *j)
if (!stbi__process_scan_header(j)) return 0;
if (!stbi__parse_entropy_coded_data(j)) return 0;
if (j->marker == STBI__MARKER_none ) {
// handle 0s at the end of image data from IP Kamera 9060
while (!stbi__at_eof(j->s)) {
int x = stbi__get8(j->s);
if (x == 255) {
j->marker = stbi__get8(j->s);
break;
}
}
j->marker = stbi__skip_jpeg_junk_at_end(j);
// if we reach eof without hitting a marker, stbi__get_marker() below will fail and we'll eventually return 0
}
} else if (stbi__DNL(m)) {