Support RGBA/BGRA Premul/Unpremul from SkPNGImageEncoder

src/images/transform_scanline.h

Index: src/images/transform_scanline.h
diff --git a/src/images/transform_scanline.h b/src/images/transform_scanline.h
index 4baf6b6c6be25cecbf150ef31509afd45203ae1a..ab970aed4cb1b1ee81ee62b9b34bd5c5f14a1cc0 100644
--- a/src/images/transform_scanline.h
+++ b/src/images/transform_scanline.h
@@ -48,17 +48,32 @@ static void transform_scanline_565(const char* SK_RESTRICT src, int width,
 }
 
 /**
- * Transform from kARGB_8888_Config to 3-bytes-per-pixel RGB.
- * Alpha channel data, if any, is abandoned.
+ * Transform from kRGBA_8888_SkColorType to 3-bytes-per-pixel RGB.
+ * Alpha channel data is abandoned.
  */
-static void transform_scanline_888(const char* SK_RESTRICT src, int width,
-                                   char* SK_RESTRICT dst) {
+static void transform_scanline_RGB1(const char* SK_RESTRICT src, int width,
+                                    char* SK_RESTRICT dst) {
+    const SkPMColor* SK_RESTRICT srcP = (const SkPMColor*)src;
+    for (int i = 0; i < width; i++) {
+        SkPMColor c = *srcP++;
+        *dst++ = (c >>  0) & 0xFF;
+        *dst++ = (c >>  8) & 0xFF;
+        *dst++ = (c >> 16) & 0xFF;
+    }
+}
+
+/**
+ * Transform from kBGRA_8888_SkColorType to 3-bytes-per-pixel RGB.
+ * Alpha channel data is abandoned.
+ */
+static void transform_scanline_BGR1(const char* SK_RESTRICT src, int width,
+                                    char* SK_RESTRICT dst) {
     const SkPMColor* SK_RESTRICT srcP = (const SkPMColor*)src;
     for (int i = 0; i < width; i++) {
         SkPMColor c = *srcP++;
-        *dst++ = SkGetPackedR32(c);
-        *dst++ = SkGetPackedG32(c);
-        *dst++ = SkGetPackedB32(c);
+        *dst++ = (c >> 16) & 0xFF;
+        *dst++ = (c >>  8) & 0xFF;
+        *dst++ = (c >>  0) & 0xFF;
     }
 }
 
@@ -78,11 +93,9 @@ static void transform_scanline_444(const char* SK_RESTRICT src, int width,
 }
 
 /**
- * Transform from kARGB_8888_Config to 4-bytes-per-pixel RGBA.
- * (This would be the identity transformation, except for byte-order and
- * scaling of RGB based on alpha channel).
+ * Transform from kPremul, kRGBA_8888_SkColorType to 4-bytes-per-pixel unpremultiplied RGBA.
  */
-static void transform_scanline_8888(const char* SK_RESTRICT src, int width,
+static void transform_scanline_rgbA(const char* SK_RESTRICT src, int width,
                                     char* SK_RESTRICT dst) {
     const SkPMColor* SK_RESTRICT srcP = (const SkPMColor*)src;
     const SkUnPreMultiply::Scale* SK_RESTRICT table =
@@ -90,10 +103,10 @@ static void transform_scanline_8888(const char* SK_RESTRICT src, int width,
 
     for (int i = 0; i < width; i++) {
         SkPMColor c = *srcP++;
-        unsigned a = SkGetPackedA32(c);
-        unsigned r = SkGetPackedR32(c);
-        unsigned g = SkGetPackedG32(c);
-        unsigned b = SkGetPackedB32(c);
+        unsigned r = (c >>  0) & 0xFF;
+        unsigned g = (c >>  8) & 0xFF;
+        unsigned b = (c >> 16) & 0xFF;
+        unsigned a = (c >> 24) & 0xFF;
 
         if (0 != a && 255 != a) {
             SkUnPreMultiply::Scale scale = table[a];
@@ -109,6 +122,56 @@ static void transform_scanline_8888(const char* SK_RESTRICT src, int width,
 }
 
 /**
+ * Transform from kPremul, kBGRA_8888_SkColorType to 4-bytes-per-pixel unpremultiplied RGBA.
+ */
+static void transform_scanline_bgrA(const char* SK_RESTRICT src, int width,
+                                    char* SK_RESTRICT dst) {
+    const SkPMColor* SK_RESTRICT srcP = (const SkPMColor*)src;
+    const SkUnPreMultiply::Scale* SK_RESTRICT table =
+                                              SkUnPreMultiply::GetScaleTable();
+
+    for (int i = 0; i < width; i++) {
+        SkPMColor c = *srcP++;
+        unsigned r = (c >> 16) & 0xFF;
+        unsigned g = (c >>  8) & 0xFF;
+        unsigned b = (c >>  0) & 0xFF;
+        unsigned a = (c >> 24) & 0xFF;
+
+        if (0 != a && 255 != a) {
+            SkUnPreMultiply::Scale scale = table[a];
+            r = SkUnPreMultiply::ApplyScale(scale, r);
+            g = SkUnPreMultiply::ApplyScale(scale, g);
+            b = SkUnPreMultiply::ApplyScale(scale, b);
+        }
+        *dst++ = r;
+        *dst++ = g;
+        *dst++ = b;
+        *dst++ = a;
+    }
+}
+
+/**
+ * Transform from kUnpremul, kRGBA_8888_SkColorType to 4-bytes-per-pixel unpremultiplied RGBA.
+ */
+static void transform_scanline_RGBA(const char* SK_RESTRICT src, int width, char* SK_RESTRICT dst) {
+    memcpy(dst, src, sizeof(SkPMColor) * width);
+}
+
+/**
+ * Transform from kUnpremul, kBGRA_8888_SkColorType to 4-bytes-per-pixel unpremultiplied RGBA.
+ */
+static void transform_scanline_BGRA(const char* SK_RESTRICT src, int width, char* SK_RESTRICT dst) {
+    const SkPMColor* SK_RESTRICT srcP = (const SkPMColor*)src;
+    for (int i = 0; i < width; i++) {
+        SkPMColor c = *srcP++;
+        *dst++ = (c >>  0) & 0xFF;
+        *dst++ = (c >>  8) & 0xFF;
+        *dst++ = (c >> 16) & 0xFF;
+        *dst++ = (c >> 24) & 0xFF;
+    }
+}
+
+/**
  * Transform from kARGB_8888_Config to 4-bytes-per-pixel RGBA,
  * with scaling of RGB based on alpha channel.
  */