add upm->upm helper

Change-Id: I912e58339b3b84be17d6a98d52cbc11f376c9a89
Reviewed-on: https://skia-review.googlesource.com/132093
Commit-Queue: Mike Klein <mtklein@chromium.org>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@chromium.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/core/SkColorSpaceXformSteps.h b/src/core/SkColorSpaceXformSteps.h
index 07e968d65e..6c38411692 100644
--- a/src/core/SkColorSpaceXformSteps.h
+++ b/src/core/SkColorSpaceXformSteps.h
@@ -15,6 +15,13 @@ struct SkColorSpaceXformSteps {
     SkColorSpaceXformSteps(SkColorSpace* src, SkAlphaType srcAT,
                            SkColorSpace* dst);
 
+    static SkColorSpaceXformSteps UnpremulToUnpremul(SkColorSpace* src, SkColorSpace* dst) {
+        // The need to transform unpremul to unpremul comes up often enough that it's
+        // nice to centralize it here, especially because this use of kOpaque_SkAlphaType
+        // isn't the most intuitive.  We basically want to always skip unpremul and premul.
+        return SkColorSpaceXformSteps(src, kOpaque_SkAlphaType, dst);
+    }
+
     bool unpremul;
     bool linearize;
     bool gamut_transform;