Unpremultiply SkBitmaps for PDF output
BUG=skia:236, chromium:175548
R=vandebo@chromium.org, edisonn@google.com, reed@google.com
Author: richardlin@chromium.org
Review URL: https://chromiumcodereview.appspot.com/22329003
git-svn-id: http://skia.googlecode.com/svn/trunk@10725 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/pdf/SkPDFImage.cpp b/src/pdf/SkPDFImage.cpp
index a5cb4c2..a4872e2 100644
--- a/src/pdf/SkPDFImage.cpp
+++ b/src/pdf/SkPDFImage.cpp
@@ -18,6 +18,57 @@
namespace {
+static void unpremultiply_and_pack_argb8888(uint32_t src, uint8_t dst[3]) {
+ uint8_t alpha = SkGetPackedA32(src);
+ if (alpha != SK_AlphaOPAQUE) {
+ SkColor unpremul = SkUnPreMultiply::PMColorToColor(src);
+ dst[0] = SkColorGetR(unpremul);
+ dst[1] = SkColorGetG(unpremul);
+ dst[2] = SkColorGetB(unpremul);
+ } else {
+ dst[0] = SkGetPackedR32(src);
+ dst[1] = SkGetPackedG32(src);
+ dst[2] = SkGetPackedB32(src);
+ }
+}
+
+static void unpremultiply_and_pack_argb4444(uint16_t src0, uint16_t src1,
+ uint8_t dst[3]) {
+ // Unpack and transform the alpha values from 4 bits to 8 bits.
+ // This is necessary since the unpremultiply functions expect to work in
+ // 8-bit space, but we are passing in 4-bit values. Since we scale up
+ // the alpha, we scale down the amount the value is increased by, so that
+ // the results are correct for 4-bit color components.
+ uint8_t alpha0 = SkGetPackedA4444(src0);
+ alpha0 = alpha0 | (alpha0 << 4);
+ if (alpha0 != SK_AlphaOPAQUE) {
+ SkUnPreMultiply::Scale scale0 = SkUnPreMultiply::GetScale(alpha0);
+ dst[0] = SkUnPreMultiply::ApplyScale(scale0,
+ SkGetPackedR4444(src0)) << 4;
+ dst[0] |= SkUnPreMultiply::ApplyScale(scale0, SkGetPackedG4444(src0));
+ dst[1] = SkUnPreMultiply::ApplyScale(scale0,
+ SkGetPackedB4444(src0)) << 4;
+ } else {
+ dst[0] = SkGetPackedR4444(src0) << 4;
+ dst[0] |= SkGetPackedG4444(src0);
+ dst[1] = SkGetPackedB4444(src0) << 4;
+ }
+
+ uint8_t alpha1 = SkGetPackedA4444(src1);
+ alpha1 = alpha1 | (alpha1 << 4);
+ if (alpha1 != SK_AlphaOPAQUE) {
+ SkUnPreMultiply::Scale scale1 = SkUnPreMultiply::GetScale(alpha1);
+ dst[1] |= SkUnPreMultiply::ApplyScale(scale1, SkGetPackedR4444(src1));
+ dst[2] = SkUnPreMultiply::ApplyScale(scale1,
+ SkGetPackedG4444(src1)) << 4;
+ dst[2] |= SkUnPreMultiply::ApplyScale(scale1, SkGetPackedB4444(src1));
+ } else {
+ dst[1] |= SkGetPackedR4444(src1);
+ dst[2] = SkGetPackedG4444(src1) << 4;
+ dst[2] |= SkGetPackedB4444(src1);
+ }
+}
+
void extractImageData(const SkBitmap& bitmap, const SkIRect& srcRect,
SkStream** imageData, SkStream** alphaData) {
SkMemoryStream* image = NULL;
@@ -49,36 +100,35 @@
uint16_t* src = bitmap.getAddr16(0, y);
int x;
for (x = srcRect.fLeft; x + 1 < srcRect.fRight; x += 2) {
- dst[0] = (SkGetPackedR4444(src[x]) << 4) |
- SkGetPackedG4444(src[x]);
- dst[1] = (SkGetPackedB4444(src[x]) << 4) |
- SkGetPackedR4444(src[x + 1]);
- dst[2] = (SkGetPackedG4444(src[x + 1]) << 4) |
- SkGetPackedB4444(src[x + 1]);
- dst += 3;
alphaDst[0] = (SkGetPackedA4444(src[x]) << 4) |
- SkGetPackedA4444(src[x + 1]);
- if (alphaDst[0] != 0xFF) {
+ SkGetPackedA4444(src[x + 1]);
+ if (alphaDst[0] != SK_AlphaOPAQUE) {
hasAlpha = true;
}
if (alphaDst[0]) {
isTransparent = false;
}
+ unpremultiply_and_pack_argb4444(src[x], src[x + 1], dst);
alphaDst++;
+ dst += 3;
}
if (srcRect.width() & 1) {
- dst[0] = (SkGetPackedR4444(src[x]) << 4) |
- SkGetPackedG4444(src[x]);
- dst[1] = (SkGetPackedB4444(src[x]) << 4);
- dst += 2;
- alphaDst[0] = (SkGetPackedA4444(src[x]) << 4);
+ alphaDst[0] = SkGetPackedA4444(src[x]) << 4;
+ // Use a buffer to translate from the usual 2 4444 values
+ // in 3 bytes to the single 4444 value in 2 bytes.
+ uint8_t buffer[3];
if (alphaDst[0] != 0xF0) {
hasAlpha = true;
}
if (alphaDst[0] & 0xF0) {
isTransparent = false;
}
+ unpremultiply_and_pack_argb4444(src[x], 0x00, buffer);
+ dst[0] = buffer[0];
+ dst[1] = buffer[1];
+
alphaDst++;
+ dst += 2;
}
}
break;
@@ -108,18 +158,16 @@
for (int y = srcRect.fTop; y < srcRect.fBottom; y++) {
uint32_t* src = bitmap.getAddr32(0, y);
for (int x = srcRect.fLeft; x < srcRect.fRight; x++) {
- dst[0] = SkGetPackedR32(src[x]);
- dst[1] = SkGetPackedG32(src[x]);
- dst[2] = SkGetPackedB32(src[x]);
- dst += 3;
alphaDst[0] = SkGetPackedA32(src[x]);
- if (alphaDst[0] != 0xFF) {
+ if (alphaDst[0] != SK_AlphaOPAQUE) {
hasAlpha = true;
}
- if (alphaDst[0]) {
+ if (alphaDst[0] != SK_AlphaTRANSPARENT) {
isTransparent = false;
}
+ unpremultiply_and_pack_argb8888(src[x], dst);
alphaDst++;
+ dst += 3;
}
}
break;