Fix some GPU image filter code to preserve precision and color space

src/effects/SkLightingImageFilter.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLightingImageFilter.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
 #include "SkPoint3.h"
 #include "SkReadBuffer.h"
 #include "SkSpecialImage.h"
 #include "SkTypes.h"
 #include "SkWriteBuffer.h"
 
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "GrDrawContext.h"
 #include "GrFixedClip.h"
 #include "GrFragmentProcessor.h"
 #include "GrInvariantOutput.h"
 #include "GrPaint.h"
 #include "SkGr.h"
+#include "SkGrPriv.h"
 #include "effects/GrSingleTextureEffect.h"
 #include "effects/GrTextureDomain.h"
 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLProgramDataManager.h"
 #include "glsl/GrGLSLUniformHandler.h"
 
 class GrGLDiffuseLightingEffect;
 class GrGLSpecularLightingEffect;
 
@@ skipping 367 matching lines @@
                                                                     SkSpecialImage* input,
                                                                     const SkIRect& offsetBounds,
                                                                     const SkMatrix& matrix) const {
     SkASSERT(source->isTextureBacked());
 
     GrContext* context = source->getContext();
 
     sk_sp<GrTexture> inputTexture(input->asTextureRef(context));
     SkASSERT(inputTexture);
 
-    sk_sp<GrDrawContext> drawContext(context->makeDrawContext(SkBackingFit::kApprox,
-                                                              offsetBounds.width(),
-                                                              offsetBounds.height(),
-                                                              kRGBA_8888_GrPixelConfig,
-                                                              sk_ref_sp(source->getColorSpace())));
+    sk_sp<GrDrawContext> drawContext(
+        context->makeDrawContext(SkBackingFit::kApprox,offsetBounds.width(), offsetBounds.height(),
+                                 GrRenderableConfigForColorSpace(source->getColorSpace()),
+                                 sk_ref_sp(source->getColorSpace())));
     if (!drawContext) {
         return nullptr;
     }
 
     SkIRect dstIRect = SkIRect::MakeWH(offsetBounds.width(), offsetBounds.height());
     SkRect dstRect = SkRect::Make(dstIRect);
 
     // setup new clip
     GrFixedClip clip(dstIRect);
 
@@ skipping 1744 matching lines @@
 
     fragBuilder->codeAppendf("%s(%s)", fLightColorFunc.c_str(), surfaceToLight);
 }
 
 #endif
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkLightingImageFilter)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkDiffuseLightingImageFilter)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkSpecularLightingImageFilter)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END