float components in xfermodes

gm/color4f.cpp

Index: gm/color4f.cpp
diff --git a/gm/color4f.cpp b/gm/color4f.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..98ce0824cca6c6231b9c6619d0b91de15d045357
--- /dev/null
+++ b/gm/color4f.cpp
@@ -0,0 +1,69 @@
+/*
+ * 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 "SkColorPriv.h"
+#include "SkShader.h"
+#include "SkSurface.h"
+
+#include "SkColorMatrixFilter.h"
+#include "SkGradientShader.h"
+
+static SkShader* make_opaque_color() {
+    return SkShader::CreateColorShader(0xFFFF0000);
+}
+
+static SkShader* make_alpha_color() {
+    return SkShader::CreateColorShader(0x80FF0000);
+}
+
+static SkColorFilter* make_cf_null() {
+    return nullptr;
+}
+
+static SkColorFilter* make_cf0() {
+    SkColorMatrix cm;
+    cm.setSaturation(0.75f);
+    return SkColorMatrixFilter::Create(cm);
+}
+
+static void draw_into_canvas(SkCanvas* canvas) {
+    const SkRect r = SkRect::MakeWH(100, 100);
+    SkShader* (*shaders[])() { make_opaque_color, make_alpha_color };
+    SkColorFilter* (*filters[])() { make_cf_null, make_cf0 };
+    
+    SkPaint paint;
+    for (auto shProc : shaders) {
+        paint.setShader(shProc())->unref();
+        for (auto cfProc : filters) {
+            SkSafeUnref(paint.setColorFilter(cfProc()));
+            canvas->drawRect(r, paint);
+            canvas->translate(120, 0);
+        }
+    }
+}
+
+DEF_SIMPLE_GM(color4f, canvas, 510, 250) {
+    canvas->translate(20, 20);
+
+    SkPaint bg;
+    // need the target to be opaque, so we can draw it to the screen
+    // even if it holds sRGB values.
+    bg.setColor(0xFFFFFFFF);
+
+    SkColorProfileType const profiles[] { kLinear_SkColorProfileType, kSRGB_SkColorProfileType };
+    for (auto profile : profiles) {
+        const SkImageInfo info = SkImageInfo::Make(500, 100, kN32_SkColorType, kPremul_SkAlphaType,
+                                                   profile);
+        SkAutoTUnref<SkSurface> surface(SkSurface::NewRaster(info));
+        surface->getCanvas()->drawPaint(bg);
+        draw_into_canvas(surface->getCanvas());
+        surface->draw(canvas, 0, 0, nullptr);
+        canvas->translate(0, 120);
+    }
+}