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Fix color channel contamination when resizing small images #2414

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Fix color channel contamination when resizing small images #2414

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2fc2755
Reset resize scanline cache between color channels
Hanabi9248 Sep 11, 2026
583879f
Cover independent channels when resizing small surfaces
Hanabi9248 Sep 11, 2026
111e424
Include resize regressions in CMake unit tests
Hanabi9248 Sep 11, 2026
9a99ad6
Include resize regressions in Visual Studio unit tests
Hanabi9248 Sep 11, 2026
6ce7b89
Include resize regressions in Xcode unit tests
Hanabi9248 Sep 11, 2026
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2 changes: 2 additions & 0 deletions src/cinder/ip/Resize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,8 @@ void resample( const vector<const ChannelT<T>*> &srcChannels, const FilterBase &
}

for( size_t chan = 0; chan < srcChannels.size(); ++chan ) {
for( auto &line : linesBuffer )
line.first = -1;
for ( int32_t dstY = 0; dstY < dstHeight; ++dstY ) { // loop over dest scanlines
// prepare a weight table for dest y position by
makeWeightTable<T,typename SCALETRAIT<T>::SUMT>( MAP(dstY, m.sy, m.uy), filter, &filterParamsY, srcHeight, false, &yWeights );
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1 change: 1 addition & 0 deletions test/unit/proj/cmake/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ set( SOURCES
${UNIT_DIR}/src/JsonTest.cpp
${UNIT_DIR}/src/ObjLoaderTest.cpp
${UNIT_DIR}/src/RandTest.cpp
${UNIT_DIR}/src/ResizeTest.cpp
${UNIT_DIR}/src/SystemTest.cpp
${UNIT_DIR}/src/ShaderPreprocessorTest.cpp
${UNIT_DIR}/src/TestMain.cpp
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49 changes: 49 additions & 0 deletions test/unit/src/ResizeTest.cpp
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Original file line number Diff line number Diff line change
@@ -0,0 +1,49 @@
#include "catch.hpp"
#include "cinder/Surface.h"
#include "cinder/ip/Resize.h"

using namespace cinder;

TEST_CASE( "Resize preserves independent color channels", "[ip]" )
{
for( int height : { 1, 2, 7 } ) {
for( bool alpha : { false, true } ) {
CAPTURE( height );
CAPTURE( alpha );
Surface8u source( 2, height, alpha );
for( int y = 0; y < height; ++y )
for( int x = 0; x < 2; ++x )
source.setPixel( ivec2( x, y ), ColorA8u( 20, 80, 160, 200 ) );

auto result = ip::resizeCopy( source, source.getBounds(), ivec2( 4, height * 2 ) );
for( int y = 0; y < result.getHeight(); ++y ) {
for( int x = 0; x < result.getWidth(); ++x ) {
auto pixel = result.getPixel( ivec2( x, y ) );
REQUIRE( pixel.r == 20 );
REQUIRE( pixel.g == 80 );
REQUIRE( pixel.b == 160 );
if( alpha )
REQUIRE( pixel.a == 200 );
}
}
}
}
}

TEST_CASE( "Resize preserves floating point color channels", "[ip]" )
{
Surface32f source( 2, 1, true );
for( int x = 0; x < 2; ++x )
source.setPixel( ivec2( x, 0 ), ColorA( 0.125f, 0.25f, 0.5f, 0.75f ) );

auto result = ip::resizeCopy( source, source.getBounds(), ivec2( 4, 2 ) );
for( int y = 0; y < result.getHeight(); ++y ) {
for( int x = 0; x < result.getWidth(); ++x ) {
auto pixel = result.getPixel( ivec2( x, y ) );
REQUIRE( pixel.r == Approx( 0.125f ) );
REQUIRE( pixel.g == Approx( 0.25f ) );
REQUIRE( pixel.b == Approx( 0.5f ) );
REQUIRE( pixel.a == Approx( 0.75f ) );
}
}
}
1 change: 1 addition & 0 deletions test/unit/vc2022/unit.vcxproj
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Original file line number Diff line number Diff line change
Expand Up @@ -522,6 +522,7 @@ xcopy /y "..\..\..\lib\msw\x86\d3dcompiler_46.dll" "$(OutDir)"</Command>
<ClCompile Include="..\src\MediaTime.cpp" />
<ClCompile Include="..\src\ObjLoaderTest.cpp" />
<ClCompile Include="..\src\RandTest.cpp" />
<ClCompile Include="..\src\ResizeTest.cpp" />
<ClCompile Include="..\src\ShaderPreprocessorTest.cpp" />
<ClCompile Include="..\src\signals\SignalsTest.cpp" />
<ClCompile Include="..\src\SystemTest.cpp" />
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3 changes: 3 additions & 0 deletions test/unit/vc2022/unit.vcxproj.filters
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,9 @@
<ClCompile Include="..\src\RandTest.cpp">
<Filter>Source Files</Filter>
</ClCompile>
<ClCompile Include="..\src\ResizeTest.cpp">
<Filter>Source Files</Filter>
</ClCompile>
<ClCompile Include="..\src\SystemTest.cpp">
<Filter>Source Files</Filter>
</ClCompile>
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4 changes: 4 additions & 0 deletions test/unit/xcode/UnitTests.xcodeproj/project.pbxproj
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
objects = {

/* Begin PBXBuildFile section */
C41D3E002026091100000001 /* ResizeTest.cpp in Sources */ = {isa = PBXBuildFile; fileRef = C41D3E002026091100000002 /* ResizeTest.cpp */; };
000703221DEB7DE00086D6CA /* Path2dTest.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 000703211DEB7DE00086D6CA /* Path2dTest.cpp */; };
AABB00011234567800CCDDEE /* CinderMathTest.cpp in Sources */ = {isa = PBXBuildFile; fileRef = AABB00001234567800CCDDEE /* CinderMathTest.cpp */; };
00C7BBC024120160001D5238 /* MediaTime.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 00C7BBBF24120160001D5238 /* MediaTime.cpp */; };
Expand Down Expand Up @@ -51,6 +52,7 @@
/* End PBXCopyFilesBuildPhase section */

/* Begin PBXFileReference section */
C41D3E002026091100000002 /* ResizeTest.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = ResizeTest.cpp; sourceTree = "<group>"; };
000703211DEB7DE00086D6CA /* Path2dTest.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Path2dTest.cpp; sourceTree = "<group>"; };
AABB00001234567800CCDDEE /* CinderMathTest.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = CinderMathTest.cpp; sourceTree = "<group>"; };
006D720219952D00008149E2 /* AVFoundation.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = AVFoundation.framework; path = System/Library/Frameworks/AVFoundation.framework; sourceTree = SDKROOT; };
Expand Down Expand Up @@ -217,6 +219,7 @@
00C7BBBF24120160001D5238 /* MediaTime.cpp */,
4989E06B1DB6889500503C9A /* PolyLineTest.cpp */,
9CA851BA1C1F74000049358B /* RandTest.cpp */,
C41D3E002026091100000002 /* ResizeTest.cpp */,
114CE0E71E2F03930002A384 /* ShaderPreprocessorTest.cpp */,
9CA851BD1C1F74000049358B /* SystemTest.cpp */,
9CA851BF1C1F74000049358B /* UnicodeTest.cpp */,
Expand Down Expand Up @@ -298,6 +301,7 @@
117BC7781E836FDF003D8F25 /* FileWatcherTest.cpp in Sources */,
9CA851C01C1F74000049358B /* Base64Test.cpp in Sources */,
9CA851C31C1F74000049358B /* RandTest.cpp in Sources */,
C41D3E002026091100000001 /* ResizeTest.cpp in Sources */,
00C7BBC024120160001D5238 /* MediaTime.cpp in Sources */,
11E4FC4D1C267DB70082A67E /* FftUnit.cpp in Sources */,
4989E06C1DB6889500503C9A /* PolyLineTest.cpp in Sources */,
Expand Down