Create special surfaces according to original device (not always in N32)

src/effects/SkDisplacementMapEffect.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDisplacementMapEffect.h"
 
 #include "SkBitmap.h"
@@ skipping 261 matching lines @@
 sk_sp<SkSpecialImage> SkDisplacementMapEffect::onFilterImage(SkSpecialImage* source,
                                                              const Context& ctx,
                                                              SkIPoint* offset) const {
     SkIPoint colorOffset = SkIPoint::Make(0, 0);
     sk_sp<SkSpecialImage> color(this->filterInput(1, source, ctx, &colorOffset));
     if (!color) {
         return nullptr;
     }
 
     SkIPoint displOffset = SkIPoint::Make(0, 0);
-    sk_sp<SkSpecialImage> displ(this->filterInput(0, source, ctx, &displOffset));
+    // Creation of the displacement map should happen in a non-colorspace aware context. This
+    // texture is a purely mathematical construct, so we want to just operate on the stored
+    // values. Consider:
+    // User supplies an sRGB displacement map. If we're rendering to a wider gamut, then we could
+    // end up filtering the displacement map into that gamut, which has the effect of reducing
+    // the amount of displacement that it represents (as encoded values move away from the
+    // primaries).
+    // With a more complex DAG attached to this input, it's not clear that working in ANY specific
+    // color space makes sense, so we ignore color spaces (and gamma) entirely. This may not be
+    // ideal, but it's at least consistent and predictable.
+    Context displContext(ctx.ctm(), ctx.clipBounds(), ctx.cache(), OutputProperties(nullptr));
+    sk_sp<SkSpecialImage> displ(this->filterInput(0, source, displContext, &displOffset));
     if (!displ) {
         return nullptr;
     }
 
     const SkIRect srcBounds = SkIRect::MakeXYWH(colorOffset.x(), colorOffset.y(),
                                                 color->width(), color->height());
 
     // Both paths do bounds checking on color pixel access, we don't need to
     // pad the color bitmap to bounds here.
     SkIRect bounds;
@@ skipping 329 matching lines @@
 void GrGLDisplacementMapEffect::GenKey(const GrProcessor& proc,
                                        const GrGLSLCaps&, GrProcessorKeyBuilder* b) {
     const GrDisplacementMapEffect& displacementMap = proc.cast<GrDisplacementMapEffect>();
 
     uint32_t xKey = displacementMap.xChannelSelector();
     uint32_t yKey = displacementMap.yChannelSelector() << kChannelSelectorKeyBits;
 
     b->add32(xKey | yKey);
 }
 #endif