Modify matrix convolution GM for sRGB testing

Tag bitmap as sRGB, and adjust gain/bias in color-managed configs to
produce results that are less blown out.

Also added a colorized version of the GM, to validate that gamut
conversion is working.

BUG=skia:

Change-Id: I333988dcdaa1272121e8aa731b4188c942fe19d8
Reviewed-on: https://skia-review.googlesource.com/6466
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 33 insertions, 8 deletions

diff --git a/gm/matrixconvolution.cpp b/gm/matrixconvolution.cpp
index 153f7a530a..ce5ce52bc9 100644
--- a/gm/matrixconvolution.cpp
+++ b/gm/matrixconvolution.cpp
@@ -7,26 +7,32 @@
 
 #include "gm.h"
 #include "SkColor.h"
-#include "SkMatrixConvolutionImageFilter.h"
 #include "SkGradientShader.h"
+#include "SkMatrixConvolutionImageFilter.h"
+#include "SkPixelRef.h"
 
 namespace skiagm {
 
 class MatrixConvolutionGM : public GM {
 public:
-    MatrixConvolutionGM() {
+    MatrixConvolutionGM(SkColor colorOne, SkColor colorTwo, const char* nameSuffix)
+            : fNameSuffix(nameSuffix) {
         this->setBGColor(0x00000000);
+        fColors[0] = colorOne;
+        fColors[1] = colorTwo;
     }
 
 protected:
 
     SkString onShortName() override {
-        return SkString("matrixconvolution");
+        return SkStringPrintf("matrixconvolution%s", fNameSuffix);
     }
 
     void makeBitmap() {
-        fBitmap.allocN32Pixels(80, 80);
-        SkCanvas canvas(fBitmap);
+        // Draw our bitmap in N32, so legacy devices get "premul" values they understand
+        SkBitmap n32Bitmap;
+        n32Bitmap.allocN32Pixels(80, 80);
+        SkCanvas canvas(n32Bitmap);
         canvas.clear(0x00000000);
         SkPaint paint;
         paint.setAntiAlias(true);
@@ -35,12 +41,15 @@ protected:
         paint.setTextSize(SkIntToScalar(180));
         SkPoint pts[2] = { SkPoint::Make(0, 0),
                            SkPoint::Make(0, SkIntToScalar(80)) };
-        SkColor colors[2] = { 0xFFFFFFFF, 0x40404040 };
         SkScalar pos[2] = { 0, SkIntToScalar(80) };
         paint.setShader(SkGradientShader::MakeLinear(
-            pts, colors, pos, 2, SkShader::kClamp_TileMode));
+            pts, fColors, pos, 2, SkShader::kClamp_TileMode));
         const char* str = "e";
         canvas.drawText(str, strlen(str), SkIntToScalar(-10), SkIntToScalar(80), paint);
+
+        // ... tag the data as sRGB, so color-aware devices do gamut adjustment, etc...
+        fBitmap.setInfo(SkImageInfo::MakeS32(80, 80, kPremul_SkAlphaType));
+        fBitmap.setPixelRef(sk_ref_sp(n32Bitmap.pixelRef()), 0, 0);
     }
 
     SkISize onISize() override {
@@ -57,6 +66,19 @@ protected:
         };
         SkISize kernelSize = SkISize::Make(3, 3);
         SkScalar gain = 0.3f, bias = SkIntToScalar(100);
+        if (canvas->imageInfo().colorSpace()) {
+            // TODO: Gain and bias are poorly specified (in the feConvolveMatrix SVG documentation,
+            // there is obviously no mention of gamma or color spaces). Eventually, we need to
+            // decide what to do with these (they generally have an extreme brightening effect).
+            // For now, I'm modifying this GM to use values tuned to preserve luminance across the
+            // range of input values (compared to the legacy math and values).
+            //
+            // It's impossible to match the results exactly, because legacy math produces a flat
+            // response (when looking at sRGB encoded results), while gamma-correct math produces
+            // a curve.
+            gain = 0.25f;
+            bias = 16.5f;
+        }
         SkPaint paint;
         paint.setImageFilter(SkMatrixConvolutionImageFilter::Make(kernelSize,
                                                                   kernel,
@@ -104,12 +126,15 @@ protected:
 
 private:
     SkBitmap fBitmap;
+    SkColor fColors[2];
+    const char* fNameSuffix;
 
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
-DEF_GM(return new MatrixConvolutionGM;)
+DEF_GM(return new MatrixConvolutionGM(0xFFFFFFFF, 0x40404040, "");)
+DEF_GM(return new MatrixConvolutionGM(0xFFFF0000, 0xFF00FF00, "_color");)
 
 }