fix trivial matrix computation

gm/downsamplebitmap.cpp

Index: gm/downsamplebitmap.cpp
diff --git a/gm/filterbitmap.cpp b/gm/downsamplebitmap.cpp
similarity index 50%
copy from gm/filterbitmap.cpp
copy to gm/downsamplebitmap.cpp
index 0afcb951018847528adb76e8c61413aff8d0ace1..a59e5b85dfb294345ebc1e5680f6a18eebd32e92 100644
--- a/gm/filterbitmap.cpp
+++ b/gm/downsamplebitmap.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 Google Inc.
+ * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
@@ -16,52 +16,17 @@ static void setTypeface(SkPaint* paint, const char name[], SkTypeface::Style sty
     SkSafeUnref(paint->setTypeface(SkTypeface::CreateFromName(name, style)));
 }
 
-static SkSize computeSize(const SkBitmap& bm, const SkMatrix& mat) {
-    SkRect bounds = SkRect::MakeWH(SkIntToScalar(bm.width()),
-                                   SkIntToScalar(bm.height()));
-    mat.mapRect(&bounds);
-    return SkSize::Make(bounds.width(), bounds.height());
-}
-
-static void draw_col(SkCanvas* canvas, const SkBitmap& bm, const SkMatrix& mat,
-                     SkScalar dx) {
-    SkPaint paint;
-
-    SkAutoCanvasRestore acr(canvas, true);
-
-    canvas->drawBitmapMatrix(bm, mat, &paint);
-
-    paint.setFilterBitmap(true);
-    canvas->translate(dx, 0);
-    canvas->drawBitmapMatrix(bm, mat, &paint);
-
-    paint.setFlags(paint.getFlags() | SkPaint::kHighQualityFilterBitmap_Flag);
-    canvas->translate(dx, 0);
-    canvas->drawBitmapMatrix(bm, mat, &paint);
-}
-
-class FilterBitmapGM : public skiagm::GM {
-    void onOnceBeforeDraw() {
-
-        make_bitmap();
-
-        SkScalar cx = SkScalarHalf(fBM.width());
-        SkScalar cy = SkScalarHalf(fBM.height());
-        SkScalar scale = get_scale();
-
-
-        fMatrix[0].setScale(scale, scale);
-        fMatrix[1].setRotate(30, cx, cy); fMatrix[1].postScale(scale, scale);
-    }
+class DownsampleBitmapGM : public skiagm::GM {
 
 public:
     SkBitmap    fBM;
-    SkMatrix    fMatrix[2];
     SkString    fName;
+    bool        fBitmapMade;
 
-    FilterBitmapGM()
+    DownsampleBitmapGM()
     {
         this->setBGColor(0xFFDDDDDD);
+        fBitmapMade = false;
     }
 
     void setName(const char name[]) {
@@ -74,47 +39,63 @@ protected:
     }
 
     virtual SkISize onISize() SK_OVERRIDE {
-        return SkISize::Make(920, 480);
+        make_bitmap_wrapper();
+        return SkISize::Make(4 * fBM.width(), fBM.height());
+    }
+
+    void make_bitmap_wrapper() {
+        if (!fBitmapMade) {
+            fBitmapMade = true;
+            make_bitmap();
+        }
     }
 
     virtual void make_bitmap() = 0;
-    virtual SkScalar get_scale() = 0;
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        make_bitmap_wrapper();
 
-        canvas->translate(10, 10);
-        for (size_t i = 0; i < SK_ARRAY_COUNT(fMatrix); ++i) {
-            SkSize size = computeSize(fBM, fMatrix[i]);
-            size.fWidth += 20;
-            size.fHeight += 20;
+        int curX = 0;
+        int curWidth;
+        float curScale = 1;
+        do {
 
-            draw_col(canvas, fBM, fMatrix[i], size.fWidth);
-            canvas->translate(0, size.fHeight);
-        }
+            SkMatrix matrix;
+            matrix.setScale( curScale, curScale );
+
+            SkPaint paint;
+            paint.setFilterBitmap(true);
+            paint.setFlags( paint.getFlags() | SkPaint::kHighQualityFilterBitmap_Flag );
+
+            canvas->save();
+            canvas->translate( (SkScalar) curX, 0.f );
+            canvas->drawBitmapMatrix( fBM, matrix, &paint );
+            canvas->restore();
+
+            curWidth = (int) (fBM.width() * curScale + 2);
+            curX += curWidth;
+            curScale *= 0.75f;
+        } while (curX < 4*fBM.width());
     }
 
 private:
     typedef skiagm::GM INHERITED;
 };
 
-class FilterBitmapTextGM: public FilterBitmapGM {
+class DownsampleBitmapTextGM: public DownsampleBitmapGM {
   public:
-      FilterBitmapTextGM(float textSize)
+      DownsampleBitmapTextGM(float textSize)
       : fTextSize(textSize)
         {
             char name[1024];
-            sprintf(name, "filterbitmap_text_%.2fpt", fTextSize);
+            sprintf(name, "downsamplebitmap_text_%.2fpt", fTextSize);
             setName(name);
         }
 
   protected:
       float fTextSize;
 
-      SkScalar get_scale() SK_OVERRIDE {
-          return 32.f/fTextSize;
-      }
-
-      void make_bitmap() SK_OVERRIDE {
+      virtual void make_bitmap() SK_OVERRIDE {
           fBM.setConfig(SkBitmap::kARGB_8888_Config, int(fTextSize * 8), int(fTextSize * 6));
           fBM.allocPixels();
           SkCanvas canvas(fBM);
@@ -135,16 +116,16 @@ class FilterBitmapTextGM: public FilterBitmapGM {
           canvas.drawText("Hamburgefons", 12, fTextSize/2, 4.8f*fTextSize, paint);
       }
   private:
-      typedef FilterBitmapGM INHERITED;
+      typedef DownsampleBitmapGM INHERITED;
 };
 
-class FilterBitmapCheckerboardGM: public FilterBitmapGM {
+class DownsampleBitmapCheckerboardGM: public DownsampleBitmapGM {
   public:
-      FilterBitmapCheckerboardGM(int size, int num_checks)
-      : fSize(size), fNumChecks(num_checks)
+      DownsampleBitmapCheckerboardGM(int size, int numChecks)
+      : fSize(size), fNumChecks(numChecks)
         {
             char name[1024];
-            sprintf(name, "filterbitmap_checkerboard_%d_%d", fSize, fNumChecks);
+            sprintf(name, "downsamplebitmap_checkerboard_%d_%d", fSize, fNumChecks);
             setName(name);
         }
 
@@ -152,16 +133,12 @@ class FilterBitmapCheckerboardGM: public FilterBitmapGM {
       int fSize;
       int fNumChecks;
 
-      SkScalar get_scale() SK_OVERRIDE {
-          return 192.f/fSize;
-      }
-
-      void make_bitmap() SK_OVERRIDE {
+      virtual void make_bitmap() SK_OVERRIDE {
           fBM.setConfig(SkBitmap::kARGB_8888_Config, fSize, fSize);
           fBM.allocPixels();
           SkAutoLockPixels lock(fBM);
-          for (int y = 0; y < fSize; y ++) {
-              for (int x = 0; x < fSize; x ++) {
+          for (int y = 0; y < fSize; ++y) {
+              for (int x = 0; x < fSize; ++x) {
                   SkPMColor* s = fBM.getAddr32(x, y);
                   int cx = (x * fNumChecks) / fSize;
                   int cy = (y * fNumChecks) / fSize;
@@ -174,16 +151,16 @@ class FilterBitmapCheckerboardGM: public FilterBitmapGM {
           }
       }
   private:
-      typedef FilterBitmapGM INHERITED;
+      typedef DownsampleBitmapGM INHERITED;
 };
 
-class FilterBitmapImageGM: public FilterBitmapGM {
+class DownsampleBitmapImageGM: public DownsampleBitmapGM {
   public:
-      FilterBitmapImageGM(const char filename[])
+      DownsampleBitmapImageGM(const char filename[])
       : fFilename(filename)
         {
             char name[1024];
-            sprintf(name, "filterbitmap_image_%s", filename);
+            sprintf(name, "downsamplebitmap_image_%s", filename);
             setName(name);
         }
 
@@ -191,11 +168,7 @@ class FilterBitmapImageGM: public FilterBitmapGM {
       SkString fFilename;
       int fSize;
 
-      SkScalar get_scale() SK_OVERRIDE {
-          return 192.f/fSize;
-      }
-
-      void make_bitmap() SK_OVERRIDE {
+      virtual void make_bitmap() SK_OVERRIDE {
           SkString path(skiagm::GM::gResourcePath);
           path.append("/");
           path.append(fFilename);
@@ -218,22 +191,11 @@ class FilterBitmapImageGM: public FilterBitmapGM {
           fSize = fBM.height();
       }
   private:
-      typedef FilterBitmapGM INHERITED;
+      typedef DownsampleBitmapGM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
-DEF_GM( return new FilterBitmapTextGM(3); )
-DEF_GM( return new FilterBitmapTextGM(7); )
-DEF_GM( return new FilterBitmapTextGM(10); )
-DEF_GM( return new FilterBitmapCheckerboardGM(4,4); )
-DEF_GM( return new FilterBitmapCheckerboardGM(32,32); )
-DEF_GM( return new FilterBitmapCheckerboardGM(32,8); )
-DEF_GM( return new FilterBitmapCheckerboardGM(32,2); )
-DEF_GM( return new FilterBitmapCheckerboardGM(192,192); )
-DEF_GM( return new FilterBitmapImageGM("mandrill_16.png"); )
-DEF_GM( return new FilterBitmapImageGM("mandrill_32.png"); )
-DEF_GM( return new FilterBitmapImageGM("mandrill_64.png"); )
-DEF_GM( return new FilterBitmapImageGM("mandrill_128.png"); )
-DEF_GM( return new FilterBitmapImageGM("mandrill_256.png"); )
-DEF_GM( return new FilterBitmapImageGM("mandrill_512.png"); )
+DEF_GM( return new DownsampleBitmapTextGM(72); )
+DEF_GM( return new DownsampleBitmapCheckerboardGM(512,256); )
+DEF_GM( return new DownsampleBitmapImageGM("mandrill_512.png"); )