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LibGfx: Parse WebP VP8X chunk

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For now, just dbgln_if() all data. Eventually we'll want to use at
least width and height.
This commit is contained in:
Nico Weber 2023-02-24 21:47:21 -05:00 • committed by Linus Groh
parent 58a5038420
commit e56e7db9d4
1 changed files with 47 additions and 3 deletions
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50
Userland/Libraries/LibGfx/WebPLoader.cpp
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@ -164,12 +164,56 @@ static ErrorOr<void> decode_webp_simple_lossless(WebPLoadingContext& context, Ch
return {};
}
static ErrorOr<void> decode_webp_chunk_VP8X(WebPLoadingContext& context, Chunk const& vp8x_chunk)
{
VERIFY(vp8x_chunk.type == FourCC("VP8X"));
// The VP8X chunk is documented at "Extended WebP file header:" at the end of
// https://developers.google.com/speed/webp/docs/riff_container#extended_file_format
if (vp8x_chunk.data.size() < 10)
return context.error("WebPImageDecoderPlugin: VP8X chunk too small");
u8 const* data = vp8x_chunk.data.data();
// 1 byte flags
// "Reserved (Rsv): 2 bits MUST be 0. Readers MUST ignore this field.
// ICC profile (I): 1 bit Set if the file contains an ICC profile.
// Alpha (L): 1 bit Set if any of the frames of the image contain transparency information ("alpha").
// Exif metadata (E): 1 bit Set if the file contains Exif metadata.
// XMP metadata (X): 1 bit Set if the file contains XMP metadata.
// Animation (A): 1 bit Set if this is an animated image. Data in 'ANIM' and 'ANMF' chunks should be used to control the animation.
// Reserved (R): 1 bit MUST be 0. Readers MUST ignore this field."
u8 flags = data[0];
bool has_icc = flags & 0x20;
bool has_alpha = flags & 0x10;
bool has_exif = flags & 0x8;
bool has_xmp = flags & 0x4;
bool has_animation = flags & 0x2;
// 3 byte reserved
// 3 byte width minus one
u32 width = (data[4] | (data[5] << 8) | (data[6] << 16)) + 1;
// 3 byte height minus one
u32 height = (data[7] | (data[8] << 8) | (data[9] << 16)) + 1;
dbgln_if(WEBP_DEBUG, "flags 0x{:x} --{}{}{}{}{}{}, width {}, height {}",
flags,
has_icc ? " icc" : "",
has_alpha ? " alpha" : "",
has_exif ? " exif" : "",
has_xmp ? " xmp" : "",
has_animation ? " anim" : "",
(flags & 0x3e) == 0 ? " none" : "",
width, height);
return {};
}
// https://developers.google.com/speed/webp/docs/riff_container#extended_file_format
static ErrorOr<void> decode_webp_extended(WebPLoadingContext& context, Chunk const& vp8x_chunk, ReadonlyBytes chunks)
{
// FIXME: Do something with this.
(void)vp8x_chunk;
TRY(decode_webp_chunk_VP8X(context, vp8x_chunk));
// FIXME: This isn't quite to spec, which says
// "All chunks SHOULD be placed in the same order as listed above.