skip transfer functions when not needed

Change-Id: I72e1084e6a14b3c1fa3f0a5c2100f13c6bcb24c7
Reviewed-on: https://skia-review.googlesource.com/130062
Commit-Queue: Mike Klein <mtklein@chromium.org>
Auto-Submit: Mike Klein <mtklein@chromium.org>
Reviewed-by: Brian Osman <brianosman@google.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/core/SkColorSpaceXformSteps.cpp b/src/core/SkColorSpaceXformSteps.cpp
index c05bf6304e..08a59fc672 100644
--- a/src/core/SkColorSpaceXformSteps.cpp
+++ b/src/core/SkColorSpaceXformSteps.cpp
@@ -83,4 +83,23 @@ SkColorSpaceXformSteps::SkColorSpaceXformSteps(SkColorSpace* src, SkAlphaType sr
 
     // Step II) if dst has linear blending, encode back using dst transfer function before storing
     this->late_encode = !dstNL;
+
+    // Fill out all the transfer functions we'll use:
+    SkColorSpaceTransferFn srcTF, dstTF;
+    SkAssertResult(src->isNumericalTransferFn(&srcTF));
+    SkAssertResult(dst->isNumericalTransferFn(&dstTF));
+    this->srcTFInv = srcTF.invert();
+    this->dstTF    = dstTF;
+    this->dstTFInv = dstTF.invert();
+
+    // If we linearize then immediately reencode with the same transfer function, skip both.
+    if ( this->linearize_src   &&
+        !this->late_unpremul   &&
+        !this->gamut_transform &&
+         this->early_encode    &&
+        0 == memcmp(&srcTF, &dstTF, sizeof(SkColorSpaceTransferFn)))
+    {
+        this->linearize_src = false;
+        this->early_encode  = false;
+    }
 }