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improve precision for blend

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git-svn-id: http://skia.googlecode.com/svn/trunk@529 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
reed@android.com 2010-03-12 19:23:27 +00:00
parent fffe48f4ac
commit 370eeeb032
1 changed files with 8 additions and 4 deletions
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12
src/effects/SkAvoidXfermode.cpp
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@ -116,6 +116,10 @@ static SkPMColor SkFourByteInterp(SkPMColor src, SkPMColor dst, unsigned scale)
return SkPackARGB32(a, r, g, b);
}
static inline unsigned Accurate255To256(unsigned x) {
return x + (x >> 7);
}
void SkAvoidXfermode::xfer32(SkPMColor dst[], const SkPMColor src[], int count,
const SkAlpha aa[])
{
@ -140,14 +144,14 @@ void SkAvoidXfermode::xfer32(SkPMColor dst[], const SkPMColor src[], int count,
// now reverse d if we need to
d = MAX + (d ^ mask) - mask;
SkASSERT((unsigned)d <= 255);
d = SkAlpha255To256(d);
d = Accurate255To256(d);
d = scale_dist_14(d, mul, sub);
SkASSERT(d <= 256);
if (d > 0) {
if (NULL != aa) {
d = SkAlphaMul(d, SkAlpha255To256(*aa++));
d = SkAlphaMul(d, Accurate255To256(*aa++));
if (0 == d) {
continue;
}
@ -198,7 +202,7 @@ void SkAvoidXfermode::xfer16(uint16_t dst[], const SkPMColor src[], int count,
if (d > 0) {
if (NULL != aa) {
d = SkAlphaMul(d, SkAlpha255To256(*aa++));
d = SkAlphaMul(d, Accurate255To256(*aa++));
if (0 == d) {
continue;
}
@ -239,7 +243,7 @@ void SkAvoidXfermode::xfer4444(uint16_t dst[], const SkPMColor src[], int count,
if (d > 0) {
if (NULL != aa) {
d = SkAlphaMul(d, SkAlpha255To256(*aa++));
d = SkAlphaMul(d, Accurate255To256(*aa++));
if (0 == d) {
continue;
}