expand gm to exercise miplevels and various scalers

gm/showmiplevels.cpp

Index: gm/showmiplevels.cpp
diff --git a/gm/showmiplevels.cpp b/gm/showmiplevels.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..385d713fe1d15e9b10913884e3975fec03804000
--- /dev/null
+++ b/gm/showmiplevels.cpp
@@ -0,0 +1,212 @@
+/*
+ * Copyright 2016 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 "Resources.h"
+#include "SkBitmapScaler.h"
+#include "SkGradientShader.h"
+#include "SkTypeface.h"
+#include "SkImageDecoder.h"
+#include "SkStream.h"
+#include "SkPaint.h"
+#include "SkMipMap.h"
+#include "Resources.h"
+#include "sk_tool_utils.h"
+
+static SkBitmap make_bitmap(int size) {
+    SkBitmap bm;
+    bm.allocN32Pixels(size, size);
+    SkCanvas canvas(bm);
+    canvas.clear(0xFFFFFFFF);
+    SkPaint paint;
+    paint.setStyle(SkPaint::kStroke_Style);
+    paint.setStrokeWidth(size / 16.0f);
+    canvas.drawCircle(size/2.0f, size/2.0f, size/3.0f, paint);
+    return bm;
+}
+
+static SkBitmap make_bitmap2(int size) {
+    SkBitmap bm;
+    bm.allocN32Pixels(size, size);
+    SkCanvas canvas(bm);
+    canvas.clear(0xFFFFFFFF);
+    SkPaint paint;
+    paint.setStyle(SkPaint::kStroke_Style);
+
+    SkScalar inset = 2;
+    SkRect r = SkRect::MakeIWH(size, size).makeInset(0.5f, 0.5f);
+    while (r.width() > 4) {
+        canvas.drawRect(r, paint);
+        r.inset(inset, inset);
+        inset += 1;
+    }
+    return bm;
+}
+
+#include "SkNx.h"
+static SkBitmap make_bitmap3(int size) {
+    SkBitmap bm;
+    bm.allocN32Pixels(size, size);
+    SkCanvas canvas(bm);
+    canvas.clear(0xFFFFFFFF);
+    SkPaint paint;
+    paint.setStyle(SkPaint::kStroke_Style);
+    paint.setStrokeWidth(2.1f);
+
+    SkScalar s = SkIntToScalar(size);
+    Sk4f p(s, -s, -s, s);
+    Sk4f d(5);
+    while (p.kth<1>() < s) {
+        canvas.drawLine(p.kth<0>(),p.kth<1>(), p.kth<2>(), p.kth<3>(), paint);
+        p = p + d;
+    }
+    return bm;
+}
+
+class ShowMipLevels : public skiagm::GM {
+    const int fN;
+    SkBitmap  fBM[4];
+
+public:
+    static unsigned gamma(unsigned n) {
+        float x = n / 255.0f;
+#if 0
+        x = sqrtf(x);
+#else
+        if (x > 0.0031308f) {
+            x = 1.055f * (powf(x, (1.0f / 2.4f))) - 0.055f;
+        } else {
+            x = 12.92f * x;
+        }
+#endif
+        return (int)(x * 255);
+    }
+
+    static void apply_gamma(const SkBitmap& bm) {
+        return; // below is our experiment for sRGB correction
+        bm.lockPixels();
+        for (int y = 0; y < bm.height(); ++y) {
+            for (int x = 0; x < bm.width(); ++x) {
+                SkPMColor c = *bm.getAddr32(x, y);
+                unsigned r = gamma(SkGetPackedR32(c));
+                unsigned g = gamma(SkGetPackedG32(c));
+                unsigned b = gamma(SkGetPackedB32(c));
+                *bm.getAddr32(x, y) = SkPackARGB32(0xFF, r, g, b);
+            }
+        }
+    }
+
+    ShowMipLevels(int N) : fN(N) {
+        fBM[0] = sk_tool_utils::create_checkerboard_bitmap(N, N, SK_ColorBLACK, SK_ColorWHITE, 2);
+        fBM[1] = make_bitmap(N);
+        fBM[2] = make_bitmap2(N);
+        fBM[3] = make_bitmap3(N);
+    }
+
+protected:
+
+    SkString onShortName() override {
+        SkString str;
+        str.printf("showmiplevels_%d", fN);
+        return str;
+    }
+
+    SkISize onISize() override {
+        return { 824, 862 };
+    }
+
+    static void DrawAndFrame(SkCanvas* canvas, const SkBitmap& orig, SkScalar x, SkScalar y) {
+        SkBitmap bm;
+        orig.copyTo(&bm);
+        apply_gamma(bm);
+
+        canvas->drawBitmap(bm, x, y, nullptr);
+        SkPaint paint;
+        paint.setStyle(SkPaint::kStroke_Style);
+        paint.setColor(0xFFFFCCCC);
+        canvas->drawRect(SkRect::MakeIWH(bm.width(), bm.height()).makeOffset(x, y).makeOutset(0.5f, 0.5f), paint);
+    }
+
+    template <typename F> void drawLevels(SkCanvas* canvas, const SkBitmap& baseBM, F func) {
+        SkScalar x = 4;
+        SkScalar y = 4;
+
+        SkPixmap prevPM;
+        baseBM.lockPixels();
+        baseBM.peekPixels(&prevPM);
+
+        SkAutoTUnref<SkMipMap> mm(SkMipMap::Build(baseBM, nullptr));
+
+        int index = 0;
+        SkMipMap::Level level;
+        SkScalar scale = 0.5f;
+        while (mm->extractLevel(scale, &level)) {
+            SkImageInfo info = SkImageInfo::MakeN32Premul(level.fWidth, level.fHeight);
+            SkPixmap levelPM{ info, level.fPixels, level.fRowBytes };
+
+            SkBitmap bm = func(prevPM, levelPM);
+            DrawAndFrame(canvas, bm, x, y);
+
+            if (info.width() <= 2 || info.height() <= 2) {
+                break;
+            }
+            if (index & 1) {
+                x += info.width() + 4;
+            } else {
+                y += info.height() + 4;
+            }
+            scale /= 2;
+            prevPM = levelPM;
+            index += 1;
+        }
+    }
+
+    void drawSet(SkCanvas* canvas, const SkBitmap& orig) {
+        SkAutoCanvasRestore acr(canvas, true);
+
+        drawLevels(canvas, orig, [](const SkPixmap& prev, const SkPixmap& curr) {
+            SkBitmap bm;
+            bm.installPixels(curr);
+            return bm;
+        });
+
+        const SkBitmapScaler::ResizeMethod methods[] = {
+            SkBitmapScaler::RESIZE_BOX,
+            SkBitmapScaler::RESIZE_TRIANGLE,
+            SkBitmapScaler::RESIZE_LANCZOS3,
+            SkBitmapScaler::RESIZE_HAMMING,
+            SkBitmapScaler::RESIZE_MITCHELL,
+        };
+
+        SkPixmap basePM;
+        orig.lockPixels();
+        orig.peekPixels(&basePM);
+        for (auto method : methods) {
+            canvas->translate(orig.width()/2 + 8.0f, 0);
+            drawLevels(canvas, orig, [basePM, method](const SkPixmap& prev, const SkPixmap& curr) {
+                SkBitmap bm;
+                SkBitmapScaler::Resize(&bm, prev, method, curr.width(), curr.height());
+                return bm;
+            });
+        }
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        canvas->translate(4, 4);
+        for (const auto& bm : fBM) {
+            this->drawSet(canvas, bm);
+            canvas->translate(0, bm.height() * 0.85f);
+        }
+    }
+    
+private:
+    typedef skiagm::GM INHERITED;
+};
+DEF_GM( return new ShowMipLevels(255); )
+DEF_GM( return new ShowMipLevels(256); )
+