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

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...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/LibPDF/Filter.cpp
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@ -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;