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Added bit bias when storing R8_UNORM to be consistent with other 8bpp #671

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Added bit bias when storing R8_UNORM to be consistent with other 8bpp #671

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18 changes: 10 additions & 8 deletions DirectXTex/DirectXTexConvert.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -194,7 +194,9 @@ namespace
const XMVECTORF32 g_Grayscale = { { { 0.2125f, 0.7154f, 0.0721f, 0.0f } } };
const XMVECTORF32 g_HalfMin = { { { -65504.f, -65504.f, -65504.f, -65504.f } } };
const XMVECTORF32 g_HalfMax = { { { 65504.f, 65504.f, 65504.f, 65504.f } } };
const XMVECTORF32 g_8BitBias = { { { 0.5f / 255.f, 0.5f / 255.f, 0.5f / 255.f, 0.5f / 255.f } } };

constexpr float g_8BitBias = 0.5f / 255.f;
const XMVECTORF32 g_8BitBiasV = { { { g_8BitBias, g_8BitBias, g_8BitBias, g_8BitBias } } };
}

//-------------------------------------------------------------------------------------
Expand Down Expand Up @@ -1762,7 +1764,7 @@ bool DirectX::Internal::StoreScanline(
for (size_t icount = 0; icount < (size - sizeof(XMUBYTEN4) + 1); icount += sizeof(XMUBYTEN4))
{
if (sPtr >= ePtr) break;
const XMVECTOR v = XMVectorAdd(*sPtr++, g_8BitBias);
const XMVECTOR v = XMVectorAdd(*sPtr++, g_8BitBiasV);
XMStoreUByteN4(dPtr++, v);
}
return true;
Expand Down Expand Up @@ -1960,7 +1962,7 @@ bool DirectX::Internal::StoreScanline(
for (size_t icount = 0; icount < size; icount += sizeof(uint8_t))
{
if (sPtr >= ePtr) break;
float v = XMVectorGetX(*sPtr++);
float v = XMVectorGetX(*sPtr++) + g_8BitBias;
v = std::max<float>(std::min<float>(v, 1.f), 0.f);
*(dPtr++) = static_cast<uint8_t>(v * 255.f);
}
Expand Down Expand Up @@ -2020,7 +2022,7 @@ bool DirectX::Internal::StoreScanline(
for (size_t icount = 0; icount < size; icount += sizeof(uint8_t))
{
if (sPtr >= ePtr) break;
float v = XMVectorGetW(*sPtr++);
float v = XMVectorGetW(*sPtr++) + g_8BitBias;
v = std::max<float>(std::min<float>(v, 1.f), 0.f);
*(dPtr++) = static_cast<uint8_t>(v * 255.f);
}
Expand Down Expand Up @@ -2065,7 +2067,7 @@ bool DirectX::Internal::StoreScanline(
const XMVECTOR v0 = *sPtr++;
const XMVECTOR v1 = (sPtr < ePtr) ? XMVectorSplatY(*sPtr++) : XMVectorZero();
XMVECTOR v = XMVectorSelect(v1, v0, g_XMSelect1110);
v = XMVectorAdd(v, g_8BitBias);
v = XMVectorAdd(v, g_8BitBiasV);
XMStoreUByteN4(dPtr++, v);
}
return true;
Expand All @@ -2084,7 +2086,7 @@ bool DirectX::Internal::StoreScanline(
const XMVECTOR v0 = XMVectorSwizzle<1, 0, 3, 2>(*sPtr++);
const XMVECTOR v1 = (sPtr < ePtr) ? XMVectorSplatY(*sPtr++) : XMVectorZero();
XMVECTOR v = XMVectorSelect(v1, v0, select1101);
v = XMVectorAdd(v, g_8BitBias);
v = XMVectorAdd(v, g_8BitBiasV);
XMStoreUByteN4(dPtr++, v);
}
return true;
Expand Down Expand Up @@ -2145,7 +2147,7 @@ bool DirectX::Internal::StoreScanline(
{
if (sPtr >= ePtr) break;
XMVECTOR v = XMVectorSwizzle<2, 1, 0, 3>(*sPtr++);
v = XMVectorAdd(v, g_8BitBias);
v = XMVectorAdd(v, g_8BitBiasV);
XMStoreUByteN4(dPtr++, v);
}
return true;
Expand All @@ -2161,7 +2163,7 @@ bool DirectX::Internal::StoreScanline(
{
if (sPtr >= ePtr) break;
XMVECTOR v = XMVectorPermute<2, 1, 0, 7>(*sPtr++, g_XMIdentityR3);
v = XMVectorAdd(v, g_8BitBias);
v = XMVectorAdd(v, g_8BitBiasV);
XMStoreUByteN4(dPtr++, v);
}
return true;
Expand Down
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