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BasisImporter: flip Y on import, if not done already #70

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BasisImporter: flip Y on import, if not done already #70

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9 changes: 3 additions & 6 deletions src/MagnumPlugins/BasisImporter/BasisImporter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -240,12 +240,9 @@ Containers::Optional<ImageData2D> BasisImporter::doImage2D(UnsignedInt index) {
CORRADE_INTERNAL_ASSERT_OUTPUT(_state->transcoder->get_image_level_desc(_state->in.data(), _state->in.size(), index, level, origWidth, origHeight, totalBlocks));

/* No flags used by transcode_image_level() by default */
const std::uint32_t flags = 0;
if(!_state->fileInfo.m_y_flipped) {
/** @todo replace with the flag once the PR is submitted */
Warning{} << "Trade::BasisImporter::image2D(): the image was not encoded Y-flipped, imported data will have wrong orientation";
//flags |= basist::basisu_transcoder::cDecodeFlagsFlipY;
}
std::uint32_t flags = 0;
if(!_state->fileInfo.m_y_flipped)
flags |= basist::basisu_transcoder::cDecodeFlagsFlipY;

Vector2i size{Int(origWidth), Int(origHeight)};
UnsignedInt dataSize, rowStride, outputSizeInBlocksOrPixels, outputRowsInPixels;
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17 changes: 0 additions & 17 deletions src/MagnumPlugins/BasisImporter/BasisImporter.h
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Expand Up @@ -111,23 +111,6 @@ OpenGL, OpenGL ES and WebGL extensions, in its full ugly glory:

<b></b>

@m_class{m-block m-warning}

@par Y-flipping
While all importers for uncompressed image data are doing an Y-flip on
import to have origin at the bottom (as expected by OpenGL), it's a
non-trivial operation with compressed images. In case of Basis, you can
pass a `-y_flip` flag to the `basisu` tool to Y-flip the image
* *during encoding*, however right now there's no way do so on import. To
inform the user, the importer checks for the Y-flip flag in the file and if
it's not there, prints a warning about the data having wrong orientation.
@par
To account for this on the application side for files that you don't have a
control of, flip texture coordinates of the mesh or patch texture data
loading in the shader.

<b></b>

@m_class{m-block m-success}

@thirdparty This plugin makes use of the
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11 changes: 3 additions & 8 deletions src/MagnumPlugins/BasisImporter/Test/BasisImporterTest.cpp
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Expand Up @@ -281,14 +281,8 @@ void BasisImporterTest::rgbUncompressedNoFlip() {
CORRADE_VERIFY(importer->openFile(Utility::Directory::join(BASISIMPORTER_TEST_DIR,
"rgb-noflip.basis")));

Containers::Optional<Trade::ImageData2D> image;
std::ostringstream out;
{
Warning redirectWarning{&out};
image = importer->image2D(0);
}
Containers::Optional<Trade::ImageData2D> image = importer->image2D(0);
CORRADE_VERIFY(image);
CORRADE_COMPARE(out.str(), "Trade::BasisImporter::image2D(): the image was not encoded Y-flipped, imported data will have wrong orientation\n");
CORRADE_VERIFY(!image->isCompressed());
CORRADE_COMPARE(image->format(), PixelFormat::RGBA8Unorm);
CORRADE_COMPARE(image->size(), (Vector2i{63, 27}));
Expand All @@ -298,7 +292,8 @@ void BasisImporterTest::rgbUncompressedNoFlip() {
if(_manager.loadState("PngImporter") == PluginManager::LoadState::NotFound)
CORRADE_SKIP("PngImporter plugin not found, cannot test contents");

CORRADE_COMPARE_WITH(Containers::arrayCast<Color3ub>(image->pixels<Color4ub>().flipped<0>()),
/* Flipping is done on import */
CORRADE_COMPARE_WITH(Containers::arrayCast<Color3ub>(image->pixels<Color4ub>()),
Utility::Directory::join(BASISIMPORTER_TEST_DIR, "rgb-63x27.png"),
/* There are moderately significant compression artifacts */
(DebugTools::CompareImageToFile{_manager, 49.67f, 8.326f}));
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