Make SkPixmap::getColor support kUnpremul pixels

Bug: skia:6319
Change-Id: Id5ad27b4e85516dfdad0c127655e6272bc0a39ac
Reviewed-on: https://skia-review.googlesource.com/19089
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>

1 files changed, 13 insertions, 6 deletions

diff --git a/src/core/SkPixmap.cpp b/src/core/SkPixmap.cpp
index 6425b29f92..9646d7c433 100644
--- a/src/core/SkPixmap.cpp
+++ b/src/core/SkPixmap.cpp
@@ -257,6 +257,13 @@ SkColor SkPixmap::getColor(int x, int y) const {
     SkASSERT(this->addr());
     SkASSERT((unsigned)x < (unsigned)this->width());
     SkASSERT((unsigned)y < (unsigned)this->height());
+
+    const bool needsUnpremul = (kPremul_SkAlphaType == fInfo.alphaType());
+    auto toColor = [needsUnpremul](uint32_t maybePremulColor) {
+        return needsUnpremul ? SkUnPreMultiply::PMColorToColor(maybePremulColor)
+                             : SkSwizzle_BGRA_to_PMColor(maybePremulColor);
+    };
+
     switch (this->colorType()) {
         case kGray_8_SkColorType: {
             uint8_t value = *this->addr8(x, y);
@@ -267,8 +274,8 @@ SkColor SkPixmap::getColor(int x, int y) const {
         }
         case kIndex_8_SkColorType: {
             SkASSERT(this->ctable());
-            SkPMColor pmColor = (*this->ctable())[*this->addr8(x, y)];
-            return SkUnPreMultiply::PMColorToColor(pmColor);
+            SkPMColor c = (*this->ctable())[*this->addr8(x, y)];
+            return toColor(c);
         }
         case kRGB_565_SkColorType: {
             return SkPixel16ToColor(*this->addr16(x, y));
@@ -276,23 +283,23 @@ SkColor SkPixmap::getColor(int x, int y) const {
         case kARGB_4444_SkColorType: {
             uint16_t value = *this->addr16(x, y);
             SkPMColor c = SkPixel4444ToPixel32(value);
-            return SkUnPreMultiply::PMColorToColor(c);
+            return toColor(c);
         }
         case kBGRA_8888_SkColorType: {
             uint32_t value = *this->addr32(x, y);
             SkPMColor c = SkSwizzle_BGRA_to_PMColor(value);
-            return SkUnPreMultiply::PMColorToColor(c);
+            return toColor(c);
         }
         case kRGBA_8888_SkColorType: {
             uint32_t value = *this->addr32(x, y);
             SkPMColor c = SkSwizzle_RGBA_to_PMColor(value);
-            return SkUnPreMultiply::PMColorToColor(c);
+            return toColor(c);
         }
         case kRGBA_F16_SkColorType: {
              const uint64_t* addr =
                  (const uint64_t*)fPixels + y * (fRowBytes >> 3) + x;
              Sk4f p4 = SkHalfToFloat_finite_ftz(*addr);
-             if (p4[3]) {
+             if (p4[3] && needsUnpremul) {
                  float inva = 1 / p4[3];
                  p4 = p4 * Sk4f(inva, inva, inva, 1);
              }