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Fix premul conversion from ARGB32 to A2RGB30 formats. 

When a premultiplied alpha changes value because it is rounded to fewer
bits the premultiplied colors may need to be recalculated with the new
value. Otherwise the color will both be wrong and potentially invalid.

Change-Id: I9ec74a22aac73cd7ffab04e180cf2bf35bb4c315
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
bb10
Allan Sandfeld Jensen 2015-05-06 14:23:57 +02:00
parent 754efa57d8
commit 8f760808e0
5 changed files with 106 additions and 2 deletions
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10
src/gui/painting/qdrawhelper.cpp
View File

@ -6640,6 +6640,10 @@ void qt_memfill32(quint32 *dest, quint32 color, int count)
}
#endif
#ifdef QT_COMPILER_SUPPORTS_SSE4_1
template<QtPixelOrder> const uint *QT_FASTCALL convertA2RGB30PMFromARGB32PM_sse4(uint *buffer, const uint *src, int count, const QPixelLayout *, const QRgb *);
#endif
void qInitDrawhelperAsm()
{
CompositionFunction *functionForModeAsm = 0;
@ -6704,7 +6708,7 @@ void qInitDrawhelperAsm()
}
#endif // SSSE3
#if QT_COMPILER_SUPPORTS_SSE4_1
#if defined(QT_COMPILER_SUPPORTS_SSE4_1)
if (qCpuHasFeature(SSE4_1)) {
#if !defined(__SSE4_1__)
extern const uint *QT_FASTCALL convertARGB32ToARGB32PM_sse4(uint *buffer, const uint *src, int count, const QPixelLayout *, const QRgb *);
@ -6718,10 +6722,12 @@ void qInitDrawhelperAsm()
qPixelLayouts[QImage::Format_ARGB32].convertFromARGB32PM = convertARGB32FromARGB32PM_sse4;
qPixelLayouts[QImage::Format_RGBA8888].convertFromARGB32PM = convertRGBA8888FromARGB32PM_sse4;
qPixelLayouts[QImage::Format_RGBX8888].convertFromARGB32PM = convertRGBXFromARGB32PM_sse4;
qPixelLayouts[QImage::Format_A2BGR30_Premultiplied].convertFromARGB32PM = convertA2RGB30PMFromARGB32PM_sse4<PixelOrderBGR>;
qPixelLayouts[QImage::Format_A2RGB30_Premultiplied].convertFromARGB32PM = convertA2RGB30PMFromARGB32PM_sse4<PixelOrderRGB>;
}
#endif
#if QT_COMPILER_SUPPORTS_AVX2 && !defined(__AVX2__)
#if defined(QT_COMPILER_SUPPORTS_AVX2) && !defined(__AVX2__)
if (qCpuHasFeature(AVX2)) {
extern const uint *QT_FASTCALL convertARGB32ToARGB32PM_avx2(uint *buffer, const uint *src, int count, const QPixelLayout *, const QRgb *);
extern const uint *QT_FASTCALL convertRGBA8888ToARGB32PM_avx2(uint *buffer, const uint *src, int count, const QPixelLayout *, const QRgb *);

17
src/gui/painting/qdrawhelper_p.h
View File

@ -847,9 +847,25 @@ template<enum QtPixelOrder> inline uint qConvertRgb32ToRgb30(QRgb);
template<enum QtPixelOrder> inline QRgb qConvertA2rgb30ToArgb32(uint c);
// A combined unpremultiply and premultiply with new simplified alpha.
// Needed when alpha loses precision relative to other colors during conversion (ARGB32 -> A2RGB30).
template<unsigned int Shift>
inline QRgb qRepremultiply(QRgb p)
{
const uint alpha = qAlpha(p);
if (alpha == 255 || alpha == 0)
return p;
p = qUnpremultiply(p);
Q_CONSTEXPR uint mult = 255 / (255 >> Shift);
const uint newAlpha = mult * (alpha >> Shift);
p = (p & ~0xff000000) | (newAlpha<<24);
return qPremultiply(p);
}
template<>
inline uint qConvertArgb32ToA2rgb30<PixelOrderBGR>(QRgb c)
{
c = qRepremultiply<6>(c);
return (c & 0xc0000000)
| (((c << 22) & 0x3fc00000) | ((c << 14) & 0x00300000))
| (((c << 4) & 0x000ff000) | ((c >> 4) & 0x00000c00))
@ -859,6 +875,7 @@ inline uint qConvertArgb32ToA2rgb30<PixelOrderBGR>(QRgb c)
template<>
inline uint qConvertArgb32ToA2rgb30<PixelOrderRGB>(QRgb c)
{
c = qRepremultiply<6>(c);
return (c & 0xc0000000)
| (((c << 6) & 0x3fc00000) | ((c >> 2) & 0x00300000))
| (((c << 4) & 0x000ff000) | ((c >> 4) & 0x00000c00))

16
src/gui/painting/qdrawhelper_sse4.cpp
View File

@ -74,6 +74,22 @@ const uint *QT_FASTCALL convertRGBXFromARGB32PM_sse4(uint *buffer, const uint *s
return buffer;
}
template<QtPixelOrder PixelOrder>
const uint *QT_FASTCALL convertA2RGB30PMFromARGB32PM_sse4(uint *buffer, const uint *src, int count,
const QPixelLayout *, const QRgb *)
{
for (int i = 0; i < count; ++i)
buffer[i] = qConvertArgb32ToA2rgb30_sse4<PixelOrder>(src[i]);
return buffer;
}
template
const uint *QT_FASTCALL convertA2RGB30PMFromARGB32PM_sse4<PixelOrderBGR>(uint *buffer, const uint *src, int count,
const QPixelLayout *, const QRgb *);
template
const uint *QT_FASTCALL convertA2RGB30PMFromARGB32PM_sse4<PixelOrderRGB>(uint *buffer, const uint *src, int count,
const QPixelLayout *, const QRgb *);
QT_END_NAMESPACE
#endif

38
src/gui/painting/qdrawingprimitive_sse2_p.h
View File

@ -35,6 +35,7 @@
#define QDRAWINGPRIMITIVE_SSE2_P_H
#include <private/qsimd_p.h>
#include "qdrawhelper_p.h"
#ifdef __SSE2__
@ -256,6 +257,43 @@ inline QRgb qUnpremultiply_sse4(QRgb p)
vl = _mm_packus_epi16(vl, vl);
return _mm_cvtsi128_si32(vl);
}
template<enum QtPixelOrder PixelOrder>
QT_FUNCTION_TARGET(SSE4_1)
inline uint qConvertArgb32ToA2rgb30_sse4(QRgb p)
{
const uint alpha = qAlpha(p);
if (alpha == 255)
return qConvertRgb32ToRgb30<PixelOrder>(p);
if (alpha == 0)
return 0;
Q_CONSTEXPR uint mult = 255 / (255 >> 6);
const uint invAlpha = qt_inv_premul_factor[alpha];
const uint newalpha = (alpha >> 6);
const __m128i via = _mm_set1_epi32(invAlpha);
const __m128i vna = _mm_set1_epi32(mult * newalpha);
const __m128i vr1 = _mm_set1_epi32(0x1000);
const __m128i vr2 = _mm_set1_epi32(0x80);
__m128i vl = _mm_cvtepu8_epi32(_mm_cvtsi32_si128(p));
vl = _mm_mullo_epi32(vl, via);
vl = _mm_add_epi32(vl, vr1);
vl = _mm_srli_epi32(vl, 14);
vl = _mm_mullo_epi32(vl, vna);
vl = _mm_add_epi32(vl, _mm_srli_epi32(vl, 8));
vl = _mm_add_epi32(vl, vr2);
vl = _mm_srli_epi32(vl, 8);
vl = _mm_packus_epi32(vl, vl);
uint rgb30 = (newalpha << 30);
rgb30 |= ((uint)_mm_extract_epi16(vl, 1)) << 10;
if (PixelOrder == PixelOrderRGB) {
rgb30 |= ((uint)_mm_extract_epi16(vl, 2)) << 20;
rgb30 |= ((uint)_mm_extract_epi16(vl, 0));
} else {
rgb30 |= ((uint)_mm_extract_epi16(vl, 0)) << 20;
rgb30 |= ((uint)_mm_extract_epi16(vl, 2));
}
return rgb30;
}
#endif
QT_END_NAMESPACE

27
tests/auto/gui/image/qimage/tst_qimage.cpp
View File

@ -190,6 +190,8 @@ private slots:
void devicePixelRatio();
void rgb30Unpremul();
void rgb30Repremul_data();
void rgb30Repremul();
void metadataPassthrough();
@ -2946,6 +2948,31 @@ void tst_QImage::rgb30Unpremul()
QCOMPARE(bbits[2], (3U << 30) | (201 << 20) | (393 << 10) | 777);
}
void tst_QImage::rgb30Repremul_data()
{
QTest::addColumn<uint>("color");
for (int i = 255; i > 0; i -= 15) {
QTest::newRow(qPrintable(QStringLiteral("100% red=") + QString::number(i))) << qRgba(i, 0, 0, 0xff);
QTest::newRow(qPrintable(QStringLiteral("75% red=") + QString::number(i))) << qRgba(i, 0, 0, 0xc0);
QTest::newRow(qPrintable(QStringLiteral("50% red=") + QString::number(i))) << qRgba(i, 0, 0, 0x80);
QTest::newRow(qPrintable(QStringLiteral("37.5% red=") + QString::number(i))) << qRgba(i, 0, 0, 0x60);
}
}
void tst_QImage::rgb30Repremul()
{
QFETCH(uint, color);
QImage a(1, 1, QImage::Format_ARGB32);
a.setPixel(0, 0, color);
QImage b = a.convertToFormat(QImage::Format_A2BGR30_Premultiplied);
b = b.convertToFormat(QImage::Format_ARGB32);
uint expectedColor = qUnpremultiply(qPremultiply(color));
uint newColor = b.pixel(0, 0);
QVERIFY(qAbs(qRed(newColor) - qRed(expectedColor)) <= 1);
}
void tst_QImage::metadataPassthrough()
{
QImage a(64, 64, QImage::Format_ARGB32);