Revert "update SkToSRGBColorFilter color management"

This reverts commit 8b5092671b1d0802e88b5202f67ceb94c9e5d236.

Reason for revert: Test if this broke Android roll

Original change's description:
> update SkToSRGBColorFilter color management
> 
> Change-Id: Ia4a8bbc9d983bb5cfa02ba62c922efa1fa879d9b
> Reviewed-on: https://skia-review.googlesource.com/141054
> Commit-Queue: Mike Klein <mtklein@chromium.org>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=mtklein@chromium.org,brianosman@google.com

Change-Id: Ib34bc4375447fe88a80d9b6d19dae87c4c41d0d5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/141180
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

1 files changed, 24 insertions, 4 deletions

diff --git a/src/effects/SkToSRGBColorFilter.cpp b/src/effects/SkToSRGBColorFilter.cpp
index 0bfa40b1d3..ba01c6b2c4 100644
--- a/src/effects/SkToSRGBColorFilter.cpp
+++ b/src/effects/SkToSRGBColorFilter.cpp
@@ -5,7 +5,6 @@
  * found in the LICENSE file.
  */
 
-#include "SkColorSpaceXformSteps.h"
 #include "SkPM4fPriv.h"
 #include "SkRasterPipeline.h"
 #include "SkReadBuffer.h"
@@ -21,9 +20,30 @@ void SkToSRGBColorFilter::onAppendStages(SkRasterPipeline* p,
                                          SkColorSpace* /*dst color space*/,
                                          SkArenaAlloc* alloc,
                                          bool shaderIsOpaque) const {
-    alloc->make<SkColorSpaceXformSteps>(fSrcColorSpace.get(), kPremul_SkAlphaType,
-                                        SkColorSpace::MakeSRGB().get())
-        ->apply(p);
+    // Step 1: Linearize by undoing the src transfer function.
+    // Linear and sRGB will return true to isNumericalTransferFn(), so we check them first.
+    SkColorSpaceTransferFn srcFn;
+    if (fSrcColorSpace->gammaIsLinear()) {
+        // Nothing to do.
+    } else if (fSrcColorSpace->gammaCloseToSRGB()) {
+        p->append(SkRasterPipeline::from_srgb);
+    } else if (fSrcColorSpace->isNumericalTransferFn(&srcFn)) {
+        auto copy = alloc->make<SkColorSpaceTransferFn>(srcFn);
+        p->append(SkRasterPipeline::parametric, copy);
+    } else {
+        SkDEBUGFAIL("Looks like we got a table transfer function here, quite unexpectedly.");
+        // TODO: If we really need to handle this, we can, but I don't think Ganesh does.
+    }
+
+    // Step 2: Transform to sRGB gamut (without clamping).
+    append_gamut_transform(p,
+                           alloc,
+                           fSrcColorSpace.get(),
+                           SkColorSpace::MakeSRGB().get(),
+                           kPremul_SkAlphaType);
+
+    // Step 3: Back to sRGB encoding.
+    p->append(SkRasterPipeline::to_srgb);
 }
 
 sk_sp<SkColorFilter> SkToSRGBColorFilter::Make(sk_sp<SkColorSpace> srcColorSpace) {