Unpremultiply SkBitmaps for PDF output

gm/bitmappremul.cpp

+/*
+ * Copyright 2013 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 "SkBitmap.h"
+#include "SkCanvas.h"
+#include "SkColorPriv.h"
+
+/**
+ * This GM checks that bitmap pixels are unpremultiplied before being exported
+ * to other formats. If unpremultiplication is implemented properly, this
+ * GM should come out completely white. If not, this GM looks like two
+ * sets of greyscale gradients.
+ * This tests both the ARGB4444 and ARGB8888 bitmap configurations.
+ */
+
+static const int SLIDE_SIZE = 256;
+static const int PIXEL_SIZE_8888 = SLIDE_SIZE / 256;
+static const int PIXEL_SIZE_4444 = SLIDE_SIZE / 16;
+
+static SkBitmap init_bitmap(SkBitmap::Config config) {
+    SkBitmap bitmap;
+    bitmap.setConfig(config, SLIDE_SIZE, SLIDE_SIZE);
+    bitmap.allocPixels();
+    bitmap.eraseColor(SK_ColorWHITE);
+    return bitmap;
+}
+
+static void populate_argb8888(SkBitmap* bitmap) {
+    uint8_t rowColor = 0;
+    for (int y = 0; y < SLIDE_SIZE; y++) {
+        uint32_t* dst = bitmap->getAddr32(0, y);
+        for (int x = 0; x < SLIDE_SIZE; x++) {
+            dst[x] = SkPackARGB32(rowColor, rowColor,
+                                  rowColor, rowColor);
+        }
+        if (y % PIXEL_SIZE_8888 == PIXEL_SIZE_8888 - 1) {
+            rowColor++;
+        }
+    }
+}
+
+static void populate_argb4444(SkBitmap* bitmap) {
+    uint8_t rowColor = 0;
+    for (int y = 0; y < SLIDE_SIZE; y++) {
+        uint16_t* dst = bitmap->getAddr16(0, y);
+        for (int x = 0; x < SLIDE_SIZE; x++) {
+            dst[x] = SkPackARGB4444(rowColor, rowColor,
+                                    rowColor, rowColor);
+        }
+        if (y % PIXEL_SIZE_4444 == PIXEL_SIZE_4444 - 1) {
+            rowColor++;
+        }
+    }
+}
+
+namespace skiagm {
+
+class BitmapPremulGM : public GM {
+public:
+    BitmapPremulGM() {
+        this->setBGColor(0xFFFFFFFF);
+    }
+
+protected:
+    SkString onShortName() SK_OVERRIDE {
+        return SkString("bitmap_premul");
+    }
+
+    virtual SkISize onISize() SK_OVERRIDE {
+        return SkISize::Make(512, 256);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        SkBitmap bitmap8888 = init_bitmap(SkBitmap::kARGB_8888_Config);
+        populate_argb8888(&bitmap8888);
+        SkBitmap bitmap4444 = init_bitmap(SkBitmap::kARGB_4444_Config);
+        populate_argb4444(&bitmap4444);
+
+        canvas->drawBitmap(bitmap8888, 0, 0);
+        canvas->drawBitmap(bitmap4444, SLIDE_SIZE, 0);
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+DEF_GM( return new BitmapPremulGM; )
+}