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LibGfx: Read webp lossless header using LittleEndianInputBitStream

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No behavior change. Covered by existing webp decoder tests :^)
This commit is contained in:
Nico Weber 2023-03-31 10:38:34 -04:00 • committed by Jelle Raaijmakers
parent a65b0cbe4a
commit 830fd0d5b2
1 changed files with 11 additions and 6 deletions
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17
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -4,9 +4,11 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/BitStream.h>
#include <AK/Debug.h>
#include <AK/Endian.h>
#include <AK/Format.h>
#include <AK/MemoryStream.h>
#include <AK/Vector.h>
#include <LibGfx/ImageFormats/WebPLoader.h>
@ -271,16 +273,19 @@ static ErrorOr<VP8LHeader> decode_webp_chunk_VP8L_header(WebPLoadingContext& con
if (vp8l_chunk.data.size() < 5)
return context.error("WebPImageDecoderPlugin: VP8L chunk too small");
u8 const* data = vp8l_chunk.data.data();
u8 signature = data[0];
FixedMemoryStream memory_stream { vp8l_chunk.data.trim(5) };
LittleEndianInputBitStream bit_stream { MaybeOwned<Stream>(memory_stream) };
u8 signature = TRY(bit_stream.read_bits(8));
if (signature != 0x2f)
return context.error("WebPImageDecoderPlugin: VP8L chunk invalid signature");
// 14 bits width-1, 14 bits height-1, 1 bit alpha hint, 3 bit version_number.
u16 width = (data[1] | ((data[2] & 0x3f) << 8)) + 1;
u16 height = ((data[2] >> 6) | (data[3] << 2) | ((data[4] & 0xf) << 12)) + 1;
bool is_alpha_used = (data[4] & 0x10) != 0;
u8 version_number = (data[4] & 0xe0) >> 5;
u16 width = TRY(bit_stream.read_bits(14)) + 1;
u16 height = TRY(bit_stream.read_bits(14)) + 1;
bool is_alpha_used = TRY(bit_stream.read_bits(1)) != 0;
u8 version_number = TRY(bit_stream.read_bits(3));
VERIFY(bit_stream.is_eof());
dbgln_if(WEBP_DEBUG, "width {}, height {}, is_alpha_used {}, version_number {}",
width, height, is_alpha_used, version_number);