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info: decode WebP dimensions

This commit is contained in:
Přemysl Eric Janouch 2023-06-05 20:54:04 +02:00
parent a9b34ca3f2
commit 399c4bdf69
Signed by: p
GPG Key ID: A0420B94F92B9493
1 changed files with 50 additions and 1 deletions
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51
tools/info.c
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@ -109,6 +109,49 @@ detect_webp(const uint8_t *p, size_t len)
return len >= 12 && !memcmp(p, "RIFF", 4) && !memcmp(p + 8, "WEBP", 4);
}
static jv
parse_webp_vp8(jv o, const uint8_t *p, size_t len)
{
if (len < 10 || (p[0] & 1) != 0 /* key frame */ ||
p[3] != 0x9d || p[4] != 0x01 || p[5] != 0x2a) {
return add_warning(o, "invalid VP8 chunk");
}
o = jv_set(o, jv_string("width"), jv_number(u16le(p + 6) & 0x3fff));
o = jv_set(o, jv_string("height"), jv_number(u16le(p + 8) & 0x3fff));
return o;
}
static jv
parse_webp_vp8l(jv o, const uint8_t *p, size_t len)
{
if (len < 5 || p[0] != 0x2f)
return add_warning(o, "invalid VP8L chunk");
// Reading LSB-first from a little endian value means reading in order.
uint32_t header = u32le(p + 1);
o = jv_set(o, jv_string("width"), jv_number((header & 0x3fff) + 1));
header >>= 14;
o = jv_set(o, jv_string("height"), jv_number((header & 0x3fff) + 1));
header >>= 14;
o = jv_set(o, jv_string("alpha_is_used"), jv_bool(header & 1));
return o;
}
static jv
parse_webp_vp8x(jv o, const uint8_t *p, size_t len)
{
if (len < 10)
return add_warning(o, "invalid VP8X chunk");
// Most of the fields in this chunk are duplicate or inferrable.
// Probably not worth decoding or verifying.
// TODO(p): For animations, we need to use the width and height from here.
uint8_t flags = p[0];
o = jv_set(o, jv_string("animation"), jv_bool((flags >> 1) & 1));
return o;
}
static jv
parse_webp(jv o, const uint8_t *p, size_t len)
{
@ -144,7 +187,13 @@ parse_webp(jv o, const uint8_t *p, size_t len)
chunks = jv_array_append(chunks, jv_string(fourcc));
p += 8;
// TODO(p): Decode VP8 and VP8L chunk metadata.
// TODO(p): Decode more chunks.
if (!strcmp(fourcc, "VP8 "))
o = parse_webp_vp8(o, p, chunk_size);
if (!strcmp(fourcc, "VP8L"))
o = parse_webp_vp8l(o, p, chunk_size);
if (!strcmp(fourcc, "VP8X"))
o = parse_webp_vp8x(o, p, chunk_size);
if (!strcmp(fourcc, "EXIF"))
o = parse_exif(o, p, chunk_size);
if (!strcmp(fourcc, "ICCP"))