extend SkShader to report a luminance-color to be used for gamma correction

gm/gammatext.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkCanvas.h"
 #include "SkPath.h"
@@ skipping 81 matching lines @@
         cgSetPaintForText(cg, paint);
 
         uint16_t glyphs[200];
         int count = paint.textToGlyphs(text, len, glyphs);
 
         CGContextShowGlyphsAtPoint(cg, x, y, glyphs, count);
     }
 }
 #endif
 
-namespace skiagm {
-
 /**
    Test a set of clipping problems discovered while writing blitAntiRect,
    and test all the code paths through the clipping blitters.
    Each region should show as a blue center surrounded by a 2px green
    border, with no red.
 */
 
 #define HEIGHT 480
 
-class GammaTextGM : public GM {
+class GammaTextGM : public skiagm::GM {
 public:
     GammaTextGM() {
 
     }
 
 protected:
     virtual SkString onShortName() {
         return SkString("gammatext");
     }
 
@@ skipping 68 matching lines @@
                 y += paint.getTextSize() * 2;
             }
             x += SkIntToScalar(1024) / SK_ARRAY_COUNT(fg);
         }
 #ifdef SK_BUILD_FOR_MAC
         CGContextRelease(cg);
 #endif
     }
 
 private:
-    typedef GM INHERITED;
+    typedef skiagm::GM INHERITED;
 };
 
+DEF_GM( return new GammaTextGM; )
+
 //////////////////////////////////////////////////////////////////////////////
 
-static GM* MyFactory(void*) { return new GammaTextGM; }
-static GMRegistry reg(MyFactory);
+static SkShader* make_gradient(SkColor c) {
+    const SkPoint pts[] = { { 0, 0 }, { 240, 0 } };
+    SkColor colors[2];
+    colors[0] = c;
+    colors[1] = SkColorSetA(c, 0);
+    return SkGradientShader::CreateLinear(pts, colors, NULL, 2, SkShader::kClamp_TileMode);
+}
 
+static void set_face(SkPaint* paint) {
+    SkTypeface* face = SkTypeface::CreateFromName("serif", SkTypeface::kItalic);
+    SkSafeUnref(paint->setTypeface(face));
 }
+
+static void draw_pair(SkCanvas* canvas, SkPaint* paint, SkShader* shader) {
+    const char text[] = "Now is the time for all good";
+    const size_t len = strlen(text);
+    
+    paint->setShader(NULL);
+    canvas->drawText(text, len, 10, 20, *paint);
+    paint->setShader(SkShader::CreateColorShader(paint->getColor()))->unref();
+    canvas->drawText(text, len, 10, 40, *paint);
+    paint->setShader(shader);
+    canvas->drawText(text, len, 10, 60, *paint);
+}
+
+class GammaShaderTextGM : public skiagm::GM {
+    SkShader* fShaders[3];
+    SkColor fColors[3];
+
+public:
+    GammaShaderTextGM() {
+        const SkColor colors[] = { SK_ColorBLACK, SK_ColorRED, SK_ColorBLUE };
+        for (size_t i = 0; i < SK_ARRAY_COUNT(fShaders); ++i) {
+            fShaders[i] = NULL;
+            fColors[i] = colors[i];
+        }
+    }
+
+    virtual ~GammaShaderTextGM() {
+        for (size_t i = 0; i < SK_ARRAY_COUNT(fShaders); ++i) {
+            SkSafeUnref(fShaders[i]);
+        }
+    }
+
+protected:
+    virtual SkString onShortName() {
+        return SkString("gammagradienttext");
+    }
+    
+    virtual SkISize onISize() {
+        return SkISize::Make(300, 300);
+    }
+
+    virtual void onOnceBeforeDraw() {
+        for (size_t i = 0; i < SK_ARRAY_COUNT(fShaders); ++i) {
+            fShaders[i] = make_gradient(fColors[i]);
+        }
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        SkPaint paint;
+        paint.setAntiAlias(true);
+        paint.setLCDRenderText(true);
+        paint.setTextSize(18);
+        set_face(&paint);
+
+        for (size_t i = 0; i < SK_ARRAY_COUNT(fShaders); ++i) {
+            paint.setColor(fColors[i]);
+            draw_pair(canvas, &paint, fShaders[i]);
+            canvas->translate(0, 80);
+        }
+    }
+    
+private:
+    typedef skiagm::GM INHERITED;
+};
+
+DEF_GM( return new GammaShaderTextGM; )
+