Implement approx-match support in image filter saveLayer() offscreen.

Currently, the GPU-side image filter implementation creates
exact-match textures for the offscreen backing stores for
saveLayer().  This is because several filters have GPU
implementations which depend on the texture coordinates
being 0..1.

The fix is three-fold:

1) Store the actual requested size in the SkGpuDevice, so
that when wrapping it in an SkBitmap for passing to
filterImage(), we can give it the original size.
2) Fix the filters (SkMagnifierImageFilter,
SkLightingImageFilter) whose GPU implementation depends on
0..1 texture coordinates.
3) Remove the exception for GPU-side image filters in
SkCanvas::internalSaveLayer().

For the lighting filters, there were two bugs which were
cancelling each other out: the sobel filter matrix was
being computed upside down, but then we'd negate the
resulting normal. This worked fine in the exact-match case,
but in the approx-match case we'd sample garbage along
the edge pixels. Also, we never implemented the edge pixels
according to spec in the GPU case. It requires a
different fragment shader for each edge of the nine-patch,
which meant we couldn't use asFragmentProcessor(), and had
to implement the drawing via a filterImageGPU() override.
In order to avoid polluting the public API, I inserted a
new base class, SkLightingImageFilterInternal above
Sk[Diffuse|Specular]LightingImageFilter to handle the
implementation.

N.B.: this change will cause some minor pixel diffs in the
GPU results of the following GMs (and possibly more):
matriximagefilter, matrixconvolution, imagefiltersscaled,
lighting, imagemagnifier, filterfastbounds,
complexclip_aa_Layer_invert, complexclip_aa_layer,
complexclip_bw_layer_invert, complexclip_bw_layer.

BUG=skia:3532

Committed: https://skia.googlesource.com/skia/+/b97dafefe63ea0a1bbce8e8b209f4920983fb8b9

Review URL: https://codereview.chromium.org/1034733002

1 files changed, 52 insertions, 9 deletions

diff --git a/gm/lighting.cpp b/gm/lighting.cpp
index 36c8ba0e45..0bfbb47a95 100644
--- a/gm/lighting.cpp
+++ b/gm/lighting.cpp
@@ -7,9 +7,10 @@
 
 #include "gm.h"
 #include "SkLightingImageFilter.h"
+#include "SkOffsetImageFilter.h"
 
 #define WIDTH 330
-#define HEIGHT 440
+#define HEIGHT 660
 
 namespace skiagm {
 
@@ -86,28 +87,70 @@ protected:
         SkPaint paint;
 
         SkImageFilter::CropRect cropRect(SkRect::MakeXYWH(20, 10, 60, 65));
+        SkImageFilter::CropRect fullSizeCropRect(SkRect::MakeXYWH(0, 0, 100, 100));
+        SkAutoTUnref<SkImageFilter> noopCropped(SkOffsetImageFilter::Create(0, 0, NULL, &cropRect));
 
         int y = 0;
-        for (int i = 0; i < 2; i++) {
-            const SkImageFilter::CropRect* cr = (i == 0) ? NULL : &cropRect;
-            paint.setImageFilter(SkLightingImageFilter::CreatePointLitDiffuse(pointLocation, white, surfaceScale, kd, NULL, cr))->unref();
+        for (int i = 0; i < 3; i++) {
+            const SkImageFilter::CropRect* cr = (i == 1) ? &cropRect : (i == 2) ? &fullSizeCropRect : NULL;
+            SkImageFilter* input = (i == 2) ? noopCropped.get() : NULL;
+            paint.setImageFilter(SkLightingImageFilter::CreatePointLitDiffuse(pointLocation,
+                                                                              white,
+                                                                              surfaceScale,
+                                                                              kd,
+                                                                              input,
+                                                                              cr))->unref();
             drawClippedBitmap(canvas, paint, 0, y);
 
-            paint.setImageFilter(SkLightingImageFilter::CreateDistantLitDiffuse(distantDirection, white, surfaceScale, kd, NULL, cr))->unref();
+            paint.setImageFilter(SkLightingImageFilter::CreateDistantLitDiffuse(distantDirection,
+                                                                                white,
+                                                                                surfaceScale,
+                                                                                kd,
+                                                                                input,
+                                                                                cr))->unref();
             drawClippedBitmap(canvas, paint, 110, y);
 
-            paint.setImageFilter(SkLightingImageFilter::CreateSpotLitDiffuse(spotLocation, spotTarget, spotExponent, cutoffAngle, white, surfaceScale, kd, NULL, cr))->unref();
+            paint.setImageFilter(SkLightingImageFilter::CreateSpotLitDiffuse(spotLocation,
+                                                                             spotTarget,
+                                                                             spotExponent,
+                                                                             cutoffAngle,
+                                                                             white,
+                                                                             surfaceScale,
+                                                                             kd,
+                                                                             input,
+                                                                             cr))->unref();
             drawClippedBitmap(canvas, paint, 220, y);
 
             y += 110;
 
-            paint.setImageFilter(SkLightingImageFilter::CreatePointLitSpecular(pointLocation, white, surfaceScale, ks, shininess, NULL, cr))->unref();
+            paint.setImageFilter(SkLightingImageFilter::CreatePointLitSpecular(pointLocation,
+                                                                               white,
+                                                                               surfaceScale,
+                                                                               ks,
+                                                                               shininess,
+                                                                               input,
+                                                                               cr))->unref();
             drawClippedBitmap(canvas, paint, 0, y);
 
-            paint.setImageFilter(SkLightingImageFilter::CreateDistantLitSpecular(distantDirection, white, surfaceScale, ks, shininess, NULL, cr))->unref();
+            paint.setImageFilter(SkLightingImageFilter::CreateDistantLitSpecular(distantDirection,
+                                                                                 white,
+                                                                                 surfaceScale,
+                                                                                 ks,
+                                                                                 shininess,
+                                                                                 input,
+                                                                                 cr))->unref();
             drawClippedBitmap(canvas, paint, 110, y);
 
-            paint.setImageFilter(SkLightingImageFilter::CreateSpotLitSpecular(spotLocation, spotTarget, spotExponent, cutoffAngle, white, surfaceScale, ks, shininess, NULL, cr))->unref();
+            paint.setImageFilter(SkLightingImageFilter::CreateSpotLitSpecular(spotLocation,
+                                                                              spotTarget,
+                                                                              spotExponent,
+                                                                              cutoffAngle,
+                                                                              white,
+                                                                              surfaceScale,
+                                                                              ks,
+                                                                              shininess,
+                                                                              input,
+                                                                              cr))->unref();
             drawClippedBitmap(canvas, paint, 220, y);
 
             y += 110;