Implement a bicubic resampling image filter, with raster and GPU backends.

In order to get this to work on the GPU side, I had to modify the width and height of the drawn texture in drawSprite() and drawDevice() to use the filtered texture's dimensions, instead of the source texture.  (This wasn't a problem before since all other image filters produce results the same dimensions as their input texture.)
For now, this implementation only does axis-aligned scaling (same as the Lanczos-3 implementation in Chrome).  It's also done for correctness and clarity, not speed, so there are lots of opportunities for speedups.

Review URL: https://codereview.appspot.com/7033049

git-svn-id: http://skia.googlecode.com/svn/trunk@7275 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 84 insertions, 0 deletions

diff --git a/gm/bicubicfilter.cpp b/gm/bicubicfilter.cpp
new file mode 100644
index 0000000000..c3f80df118
--- /dev/null
+++ b/gm/bicubicfilter.cpp
@@ -0,0 +1,84 @@
+/*
+ * 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 "SkColor.h"
+#include "SkBicubicImageFilter.h"
+
+namespace skiagm {
+
+class BicubicGM : public GM {
+public:
+    BicubicGM() : fInitialized(false) {
+        this->setBGColor(0x00000000);
+    }
+
+protected:
+    virtual SkString onShortName() {
+        return SkString("bicubicfilter");
+    }
+
+    void make_checkerboard(int width, int height) {
+        SkASSERT(width % 2 == 0);
+        SkASSERT(height % 2 == 0);
+        fCheckerboard.setConfig(SkBitmap::kARGB_8888_Config, width, height);
+        fCheckerboard.allocPixels();
+        SkAutoLockPixels lock(fCheckerboard);
+        for (int y = 0; y < height; y += 2) {
+            SkPMColor* s = fCheckerboard.getAddr32(0, y);
+            for (int x = 0; x < width; x += 2) {
+                *s++ = 0xFFFFFFFF;
+                *s++ = 0xFF000000;
+            }
+            s = fCheckerboard.getAddr32(0, y + 1);
+            for (int x = 0; x < width; x += 2) {
+                *s++ = 0xFF000000;
+                *s++ = 0xFFFFFFFF;
+            }
+        }
+    }
+
+    virtual SkISize onISize() {
+        return make_isize(400, 300);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        if (!fInitialized) {
+            make_checkerboard(4, 4);
+            fInitialized = true;
+        }
+        SkScalar sk32 = SkIntToScalar(32);
+        canvas->clear(0x00000000);
+        SkPaint bilinearPaint, bicubicPaint;
+        SkSize scale = SkSize::Make(sk32, sk32);
+        canvas->save();
+        canvas->scale(sk32, sk32);
+        bilinearPaint.setFilterBitmap(true);
+        canvas->drawBitmap(fCheckerboard, 0, 0, &bilinearPaint);
+        canvas->restore();
+        SkAutoTUnref<SkImageFilter> bicubic(SkBicubicImageFilter::CreateMitchell(scale));
+        bicubicPaint.setImageFilter(bicubic);
+        SkRect srcBounds;
+        fCheckerboard.getBounds(&srcBounds);
+        canvas->translate(SkIntToScalar(140), 0);
+        canvas->saveLayer(&srcBounds, &bicubicPaint);
+        canvas->drawBitmap(fCheckerboard, 0, 0);
+        canvas->restore();
+    }
+
+private:
+    typedef GM INHERITED;
+    SkBitmap fCheckerboard;
+    bool fInitialized;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static GM* MyFactory(void*) { return new BicubicGM; }
+static GMRegistry reg(MyFactory);
+
+}