add gm to show miplevels

gm/downsamplebitmap.cpp

Index: gm/downsamplebitmap.cpp
diff --git a/gm/downsamplebitmap.cpp b/gm/downsamplebitmap.cpp
index ce10b47a84d6acd7d31aefcdbeb720a1f1a2ea91..50b15494b6f04771ffdf10bee90d1b07070c8e2a 100644
--- a/gm/downsamplebitmap.cpp
+++ b/gm/downsamplebitmap.cpp
@@ -14,6 +14,22 @@
 #include "SkStream.h"
 #include "SkPaint.h"
 
+static void make_checker(SkBitmap* bm, int size, int numChecks) {
+    bm->allocN32Pixels(size, size);
+    for (int y = 0; y < size; ++y) {
+        for (int x = 0; x < size; ++x) {
+            SkPMColor* s = bm->getAddr32(x, y);
+            int cx = (x * numChecks) / size;
+            int cy = (y * numChecks) / size;
+            if ((cx+cy)%2) {
+                *s = 0xFFFFFFFF;
+            } else {
+                *s = 0xFF000000;
+            }
+        }
+    }
+}
+
 static void setTypeface(SkPaint* paint, const char name[], SkTypeface::Style style) {
     sk_tool_utils::set_portable_typeface(paint, name, style);
 }
@@ -139,19 +155,7 @@ class DownsampleBitmapCheckerboardGM: public DownsampleBitmapGM {
       int fNumChecks;
 
       void make_bitmap() SK_OVERRIDE {
-          fBM.allocN32Pixels(fSize, fSize);
-          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;
-                  if ((cx+cy)%2) {
-                      *s = 0xFFFFFFFF;
-                  } else {
-                      *s = 0xFF000000;
-                  }
-              }
-          }
+          make_checker(&fBM, fSize, fNumChecks);
       }
   private:
       typedef DownsampleBitmapGM INHERITED;
@@ -190,6 +194,59 @@ class DownsampleBitmapImageGM: public DownsampleBitmapGM {
       typedef DownsampleBitmapGM INHERITED;
 };
 
+#include "SkMipMap.h"
+class ShowMipLevels : public skiagm::GM {
+public:
+    SkBitmap    fBM;
+
+    ShowMipLevels() {
+        this->setBGColor(0xFFDDDDDD);
+        make_checker(&fBM, 512, 256);
+    }
+
+protected:
+#if 0
+    uint32_t onGetFlags() const SK_OVERRIDE {
+        return kSkipTiled_Flag;
+    }
+#endif
+
+    SkString onShortName() SK_OVERRIDE {
+        return SkString("showmiplevels");
+    }
+
+    SkISize onISize() SK_OVERRIDE {
+        return SkISize::Make(fBM.width() + 4, 4 * fBM.height());
+    }
+
+    void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        SkScalar x = 4;
+        SkScalar y = 4;
+        canvas->drawBitmap(fBM, x, y, NULL);
+        y += fBM.height() + 4;
+
+        SkMipMap* mm = SkMipMap::Build(fBM, NULL);
+
+        SkMipMap::Level level;
+        SkScalar scale = 0.5f;
+        while (mm->extractLevel(scale, &level)) {
+            SkImageInfo info = SkImageInfo::MakeN32Premul(level.fWidth, level.fHeight);
+            SkBitmap bm;
+            bm.installPixels(info, level.fPixels, level.fRowBytes);
+            canvas->drawBitmap(bm, x, y, NULL);
+            y += bm.height() + 4;
+            scale /= 2;
+            if (info.width() == 1 || info.height() == 1) {
+                break;
+            }
+        }
+    }
+    
+private:
+    typedef skiagm::GM INHERITED;
+};
+
+
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new DownsampleBitmapTextGM(72, SkPaint::kHigh_FilterLevel); )
@@ -215,3 +272,5 @@ DEF_GM( return new DownsampleBitmapCheckerboardGM(512,256, SkPaint::kNone_Filter
 DEF_GM( return new DownsampleBitmapImageGM("mandrill_512.png", SkPaint::kNone_FilterLevel); )
 DEF_GM( return new DownsampleBitmapImageGM("mandrill_132x132_12x12.astc",
                                            SkPaint::kNone_FilterLevel); )
+
+DEF_GM( return new ShowMipLevels; )