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LibGfx+LibPDF: Create filter_type() for converting u8 to FilterType

Browse source 
...and use it in LibPDF.

No behavior change.
This commit is contained in:
Nico Weber 2023-11-16 19:37:42 -05:00 • committed by Andreas Kling
parent 7e4fe8e610
commit 588d6fab22
3 changed files with 23 additions and 17 deletions
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16
Userland/Libraries/LibGfx/ImageFormats/PNGLoader.cpp
View file

@ -698,18 +698,18 @@ static ErrorOr<void> decode_png_bitmap_simple(PNGLoadingContext& context, ByteBu
Streamer streamer(decompression_buffer.data(), decompression_buffer.size());
for (int y = 0; y < context.height; ++y) {
PNG::FilterType filter;
if (!streamer.read(filter)) {
u8 filter_byte;
if (!streamer.read(filter_byte)) {
context.state = PNGLoadingContext::State::Error;
return Error::from_string_literal("PNGImageDecoderPlugin: Decoding failed");
}
if (to_underlying(filter) > 4) {
if (filter_byte > 4) {
context.state = PNGLoadingContext::State::Error;
return Error::from_string_literal("PNGImageDecoderPlugin: Invalid PNG filter");
}
context.scanlines.append({ filter });
context.scanlines.append({ MUST(PNG::filter_type(filter_byte)) });
auto& scanline_buffer = context.scanlines.last().data;
auto row_size = context.compute_row_size_for_width(context.width);
if (row_size.has_overflow())
@ -784,18 +784,18 @@ static ErrorOr<void> decode_adam7_pass(PNGLoadingContext& context, Streamer& str
return {};
for (int y = 0; y < subimage_context.height; ++y) {
PNG::FilterType filter;
if (!streamer.read(filter)) {
u8 filter_byte;
if (!streamer.read(filter_byte)) {
context.state = PNGLoadingContext::State::Error;
return Error::from_string_literal("PNGImageDecoderPlugin: Decoding failed");
}
if (to_underlying(filter) > 4) {
if (filter_byte > 4) {
context.state = PNGLoadingContext::State::Error;
return Error::from_string_literal("PNGImageDecoderPlugin: Invalid PNG filter");
}
subimage_context.scanlines.append({ filter });
subimage_context.scanlines.append({ MUST(PNG::filter_type(filter_byte)) });
auto& scanline_buffer = subimage_context.scanlines.last().data;
auto row_size = context.compute_row_size_for_width(subimage_context.width);

8
Userland/Libraries/LibGfx/ImageFormats/PNGShared.h
View file

@ -7,6 +7,7 @@
#pragma once
#include <AK/Array.h>
#include <AK/Error.h>
#include <AK/SIMD.h>
namespace Gfx::PNG {
@ -32,6 +33,13 @@ enum class FilterType : u8 {
Paeth,
};
inline ErrorOr<FilterType> filter_type(u8 byte)
{
if (byte <= 4)
return static_cast<FilterType>(byte);
return Error::from_string_literal("PNGImageDecoderPlugin: Invalid PNG filter");
}
// https://www.w3.org/TR/PNG/#9Filter-type-4-Paeth
ALWAYS_INLINE u8 paeth_predictor(u8 a, u8 b, u8 c)
{

16
Userland/Libraries/LibPDF/Filter.cpp
View file

@ -162,19 +162,19 @@ PDFErrorOr<ByteBuffer> Filter::decode_png_prediction(Bytes bytes, int bytes_per_
for (int row_index = 0; row_index < number_of_rows; ++row_index) {
auto row = bytes.data() + row_index * bytes_per_row;
u8 algorithm_tag = row[0];
switch (algorithm_tag) {
case 0:
auto filter = TRY(Gfx::PNG::filter_type(row[0]));
switch (filter) {
case Gfx::PNG::FilterType::None:
break;
case 1:
case Gfx::PNG::FilterType::Sub:
for (int i = 2; i < bytes_per_row; ++i)
row[i] += row[i - 1];
break;
case 2:
case Gfx::PNG::FilterType::Up:
for (int i = 1; i < bytes_per_row; ++i)
row[i] += previous_row[i];
break;
case 3:
case Gfx::PNG::FilterType::Average:
for (int i = 1; i < bytes_per_row; ++i) {
u8 left = 0;
if (i > 1)
@ -183,7 +183,7 @@ PDFErrorOr<ByteBuffer> Filter::decode_png_prediction(Bytes bytes, int bytes_per_
row[i] += (left + above) / 2;
}
break;
case 4:
case Gfx::PNG::FilterType::Paeth:
for (int i = 1; i < bytes_per_row; ++i) {
u8 left = 0;
u8 upper_left = 0;
@ -195,8 +195,6 @@ PDFErrorOr<ByteBuffer> Filter::decode_png_prediction(Bytes bytes, int bytes_per_
row[i] += Gfx::PNG::paeth_predictor(left, above, upper_left);
}
break;
default:
return AK::Error::from_string_literal("Unknown PNG algorithm tag");
}
previous_row = row;