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Alpha channel should be 1 by default, rather than 0 #2197

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Alpha channel should be 1 by default, rather than 0 #2197

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1ff4a21
For CPU processor, when source has no alpha make it default to 1.
pennelee Sep 25, 2025
c7b025e
Fix alpha channel for integer types.
pennelee Jan 31, 2026
24c6395
Merge branch 'AcademySoftwareFoundation:main' into feature/1781_2025_…
pennelee Feb 1, 2026
6ffa259
Fix max alpha value to be from input bitdepth not output.
pennelee Feb 3, 2026
fc66696
Forgot to update ImagePacking.h
pennelee Feb 3, 2026
63b7b7a
Merge branch 'AcademySoftwareFoundation:main' into feature/1781_2025_…
pennelee Feb 3, 2026
5a4085b
Remove the unused inputBitDepth name causing compiler error.
pennelee Feb 3, 2026
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18 changes: 13 additions & 5 deletions src/OpenColorIO/ImagePacking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,8 @@ void Generic<Type>::PackRGBAFromImageDesc(const GenericImageDesc & srcImg,
Type * inBitDepthBuffer,
float * outputBuffer,
int outputBufferSize,
long imagePixelStartIndex)
long imagePixelStartIndex,
BitDepth inputBitDepth)
{
if(outputBuffer==nullptr)
{
Expand Down Expand Up @@ -62,15 +63,21 @@ void Generic<Type>::PackRGBAFromImageDesc(const GenericImageDesc & srcImg,
aPtr = reinterpret_cast<Type*>(aRow + xStrideBytes*xIndex);
}

float maxValue = static_cast<float>(GetBitDepthMaxValue(inputBitDepth));
if (maxValue <= 0)
{
throw Exception("Invalid bit depth max value.");
}

// Process one single, complete scanline.
int pixelsCopied = 0;
while(pixelsCopied < outputBufferSize)
{
{
// Reorder channels from arbitrary channel ordering to RGBA 32-bit float.
inBitDepthBuffer[4*pixelsCopied+0] = *rPtr;
inBitDepthBuffer[4*pixelsCopied+1] = *gPtr;
inBitDepthBuffer[4*pixelsCopied+2] = *bPtr;
inBitDepthBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : (Type)0.0f;
inBitDepthBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : (Type)(maxValue);

pixelsCopied++;
xIndex++;
Expand All @@ -93,7 +100,8 @@ void Generic<float>::PackRGBAFromImageDesc(const GenericImageDesc & srcImg,
float * /*inBitDepthBuffer*/,
float * outputBuffer,
int outputBufferSize,
long imagePixelStartIndex)
long imagePixelStartIndex,
BitDepth /*inputBitDepth*/)
{
if(outputBuffer==nullptr)
{
Expand Down Expand Up @@ -140,7 +148,7 @@ void Generic<float>::PackRGBAFromImageDesc(const GenericImageDesc & srcImg,
outputBuffer[4*pixelsCopied+0] = *rPtr;
outputBuffer[4*pixelsCopied+1] = *gPtr;
outputBuffer[4*pixelsCopied+2] = *bPtr;
outputBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : 0.0f;
outputBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : (float)1.0f;
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@cozdas cozdas Feb 3, 2026

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Suggested change
outputBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : (float)1.0f;
outputBuffer[4*pixelsCopied+3] = aPtr ? *aPtr : 1.0f;


pixelsCopied++;
xIndex++;
Expand Down
3 changes: 2 additions & 1 deletion src/OpenColorIO/ImagePacking.h
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,8 @@ struct Generic
Type * inBitDepthBuffer,
float * outputBuffer,
int outputBufferSize,
long imagePixelStartIndex);
long imagePixelStartIndex,
BitDepth inputBitDepth);

static void UnpackRGBAToImageDesc(GenericImageDesc & dstImg,
float * inputBuffer,
Expand Down
3 changes: 2 additions & 1 deletion src/OpenColorIO/ScanlineHelper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -143,7 +143,8 @@ void GenericScanlineHelper<InType, OutType>::prepRGBAScanline(float** buffer, lo
&m_inBitDepthBuffer[0],
*buffer,
m_dstImg.m_width,
m_yIndex * m_dstImg.m_width);
m_yIndex * m_dstImg.m_width,
m_inputBitDepth);
}

numPixels = m_dstImg.m_width;
Expand Down
46 changes: 23 additions & 23 deletions tests/cpu/CPUProcessor_tests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -276,9 +276,9 @@ OCIO_ADD_TEST(CPUProcessor, with_one_matrix)
1.0000f, 1.2500f, 1.9900f };

const std::vector<float> resImg
= { -0.01929f, -0.3995f, 0.4002f, 0.5f,
1.58960f, 0.9050f, 1.5025f, 0.5f,
2.070699f, 1.6505f, 2.4002f, 0.5f };
= { -0.01929f, -0.3995f, 0.4002f, 1.5f,
1.58960f, 0.9050f, 1.5025f, 1.5f,
2.070699f, 1.6505f, 2.4002f, 1.5f };

ComputeValues<OCIO::BIT_DEPTH_F32, OCIO::BIT_DEPTH_F32>(
__LINE__, processor,
Expand Down Expand Up @@ -620,10 +620,10 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
5120, 20480, 65535 };

const std::vector<uint16_t> resImg
= { 95, 24, 0, 0,
268, 178, 123, 0,
955, 598, 394, 0,
65535, 8589, 1986, 0 };
= { 95, 24, 0, 65535,
268, 178, 123, 65535,
955, 598, 394, 65535,
65535, 8589, 1986, 65535 };

ComputeValues<OCIO::BIT_DEPTH_UINT16, OCIO::BIT_DEPTH_UINT16>(
__LINE__, processor,
Expand Down Expand Up @@ -656,10 +656,10 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
128, 1023, 640 };

const std::vector<uint16_t> ui10_resImg
= { 0, 6, 15, 0,
26, 48, 106, 0,
36, 106, 252, 0,
48, 1023, 384, 0 };
= { 0, 6, 15, 1023,
26, 48, 106, 1023,
36, 106, 252, 1023,
48, 1023, 384, 1023 };

ComputeValues<OCIO::BIT_DEPTH_UINT10, OCIO::BIT_DEPTH_UINT10>(
__LINE__, processor,
Expand All @@ -668,10 +668,10 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
NB_PIXELS);

const std::vector<uint16_t> ui16_resImg
= { 0, 394, 955, 0,
1656, 3092, 6794, 0,
2301, 6794, 16162, 0,
3092, 65535, 24593, 0 };
= { 0, 394, 955, 65535,
1656, 3092, 6794, 65535,
2301, 6794, 16162, 65535,
3092, 65535, 24593, 65535 };

ComputeValues<OCIO::BIT_DEPTH_UINT10, OCIO::BIT_DEPTH_UINT16>(
__LINE__, processor,
Expand Down Expand Up @@ -704,21 +704,21 @@ OCIO_ADD_TEST(CPUProcessor, with_one_1d_lut)
1024, 2048, 4095 };

const std::vector<uint16_t> ui12_resImg
= { 0, 11, 25, 0,
37, 60, 103, 0,
49, 103, 193, 0,
424, 1009, 4095, 0 };
= { 0, 11, 25, 4095,
37, 60, 103, 4095,
49, 103, 193, 4095,
424, 1009, 4095, 4095 };

ComputeValues<OCIO::BIT_DEPTH_UINT12, OCIO::BIT_DEPTH_UINT12>(
__LINE__, processor,
&ui12_inImg[0], OCIO::CHANNEL_ORDERING_RGB,
&ui12_resImg[0], OCIO::CHANNEL_ORDERING_RGBA,
NB_PIXELS);
const std::vector<uint16_t> ui16_resImg
= { 0, 178, 394, 0,
598, 955, 1655, 0,
779, 1655, 3089, 0,
6789, 16143, 65535, 0 };
= { 0, 178, 394, 65535,
598, 955, 1655, 65535,
779, 1655, 3089, 65535,
6789, 16143, 65535, 65535 };

ComputeValues<OCIO::BIT_DEPTH_UINT12, OCIO::BIT_DEPTH_UINT16>(
__LINE__, processor,
Expand Down