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Fix QPainter's ColorDodge and ColorBurn composition modes

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Added checking corner cases (more specific formulas) in
color_dodge_op()/color_dodge_op_rgb64() and color_burn_op()/color_burn_op_rgb64()
to produce correct results for any input.

Task-number: QTBUG-77231
Change-Id: I274f80b356bd4236a9176a84a95604c2eb01787a
Reviewed-by: Konstantin Tokarev <annulen@yandex.ru>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
This commit is contained in:
Pavel Artsishevsky 2019-07-30 04:04:45 +03:00
parent ec62033bc2
commit a22bb694ce
1 changed files with 18 additions and 6 deletions
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24
src/gui/painting/qcompositionfunctions.cpp
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@ -1763,8 +1763,10 @@ void QT_FASTCALL comp_func_Lighten_rgb64(QRgba64 *Q_DECL_RESTRICT dest, const QR
}
/*
if Sca.Da + Dca.Sa >= Sa.Da
if Sca.Da + Dca.Sa > Sa.Da
Dca' = Sa.Da + Sca.(1 - Da) + Dca.(1 - Sa)
else if Sca == Sa
Dca' = Dca.Sa + Sca.(1 - Da) + Dca.(1 - Sa)
otherwise
Dca' = Dca.Sa/(1-Sca/Sa) + Sca.(1 - Da) + Dca.(1 - Sa)
*/
@ -1775,8 +1777,10 @@ static inline int color_dodge_op(int dst, int src, int da, int sa)
const int src_da = src * da;
const int temp = src * (255 - da) + dst * (255 - sa);
if (src_da + dst_sa >= sa_da)
if (src_da + dst_sa > sa_da)
return qt_div_255(sa_da + temp);
else if (src == sa || sa == 0)
return qt_div_255(temp);
else
return qt_div_255(255 * dst_sa / (255 - 255 * src / sa) + temp);
}
@ -1788,8 +1792,10 @@ static inline uint color_dodge_op_rgb64(qint64 dst, qint64 src, qint64 da, qint6
const qint64 src_da = src * da;
const qint64 temp = src * (65535 - da) + dst * (65535 - sa);
if (src_da + dst_sa >= sa_da)
if (src_da + dst_sa > sa_da)
return qt_div_65535(sa_da + temp);
else if (src == sa || sa == 0)
return qt_div_65535(temp);
else
return qt_div_65535(65535 * dst_sa / (65535 - 65535 * src / sa) + temp);
}
@ -1915,8 +1921,10 @@ void QT_FASTCALL comp_func_ColorDodge_rgb64(QRgba64 *Q_DECL_RESTRICT dest, const
}
/*
if Sca.Da + Dca.Sa <= Sa.Da
if Sca.Da + Dca.Sa < Sa.Da
Dca' = Sca.(1 - Da) + Dca.(1 - Sa)
else if Sca == 0
Dca' = Dca.Sa + Sca.(1 - Da) + Dca.(1 - Sa)
otherwise
Dca' = Sa.(Sca.Da + Dca.Sa - Sa.Da)/Sca + Sca.(1 - Da) + Dca.(1 - Sa)
*/
@ -1928,8 +1936,10 @@ static inline int color_burn_op(int dst, int src, int da, int sa)
const int temp = src * (255 - da) + dst * (255 - sa);
if (src == 0 || src_da + dst_sa <= sa_da)
if (src_da + dst_sa < sa_da)
return qt_div_255(temp);
else if (src == 0)
return qt_div_255(dst_sa + temp);
return qt_div_255(sa * (src_da + dst_sa - sa_da) / src + temp);
}
@ -1941,8 +1951,10 @@ static inline uint color_burn_op_rgb64(qint64 dst, qint64 src, qint64 da, qint64
const qint64 temp = src * (65535 - da) + dst * (65535 - sa);
if (src == 0 || src_da + dst_sa <= sa_da)
if (src_da + dst_sa < sa_da)
return qt_div_65535(temp);
else if (src == 0)
return qt_div_65535(dst_sa + temp);
return qt_div_65535(sa * (src_da + dst_sa - sa_da) / src + temp);
}