Improve color type handling in SkImage_Base::makeColorSpace()

Color space xforms  with Alpha8 images are no-ops.
Other xforms should use 8888 as dst color type.

BUG=skia:

Change-Id: Iede3d94d23c8f4c3dabdaa5450af7b5bfff8d24f
Reviewed-on: https://skia-review.googlesource.com/9996
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Matt Sarett <msarett@google.com>

2 files changed, 12 insertions, 8 deletions

diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index fe6369ed35..566bdc092f 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -308,9 +308,12 @@ sk_sp<SkImage> SkImage_Base::makeColorSpace(sk_sp<SkColorSpace> target) const {
         return nullptr;
     }
 
-    // Be sure to treat nullptr srcs as "equal to" sRGB.
+    // No need to create a new image if:
+    // (1) The color spaces are equal (nullptr is considered to be sRGB).
+    // (2) The color type is kAlpha8.
     if ((!this->colorSpace() && target->isSRGB()) ||
-            SkColorSpace_Base::EqualsIgnoreFlags(this->colorSpace(), target.get())) {
+            SkColorSpace_Base::EqualsIgnoreFlags(this->colorSpace(), target.get()) ||
+            kAlpha_8_SkColorType == this->onImageInfo().colorType()) {
         return sk_ref_sp(const_cast<SkImage_Base*>(this));
     }
 
diff --git a/src/image/SkImage_Raster.cpp b/src/image/SkImage_Raster.cpp
index 26f43c7e1f..388c8da196 100644
--- a/src/image/SkImage_Raster.cpp
+++ b/src/image/SkImage_Raster.cpp
@@ -371,13 +371,14 @@ bool SkImage_Raster::onAsLegacyBitmap(SkBitmap* bitmap, LegacyBitmapMode mode) c
 }
 
 sk_sp<SkImage> SkImage_Raster::onMakeColorSpace(sk_sp<SkColorSpace> target) const {
+    // Force the color type of the new image to be kN32_SkColorType.
+    // (1) This means we lose precision on F16 images.  This is necessary while this function is
+    //     used to pre-transform inputs to a legacy canvas.  Legacy canvases do not handle F16.
+    // (2) kIndex8 and kGray8 must be expanded in order perform a color space transformation.
+    // (3) Seems reasonable to expand k565 and k4444.  It's nice to avoid these color types for
+    //     clients who opt into color space support.
+    SkImageInfo dstInfo = fBitmap.info().makeColorType(kN32_SkColorType).makeColorSpace(target);
     SkBitmap dst;
-    SkImageInfo dstInfo = fBitmap.info().makeColorSpace(target);
-    if (kIndex_8_SkColorType == dstInfo.colorType() ||
-        kGray_8_SkColorType == dstInfo.colorType())
-    {
-        dstInfo = dstInfo.makeColorType(kN32_SkColorType);
-    }
     dst.allocPixels(dstInfo);
 
     SkPixmap src;