samplecode/SampleSubpixelTranslate.cpp

/*
 * Copyright 2014 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 "SampleCode.h"
#include "SkBlurMaskFilter.h"
#include "SkCanvas.h"
#include "SkColorPriv.h"
#include "SkImageDecoder.h"
#include "SkRandom.h"
#include "SkStream.h"

// Intended to exercise pixel snapping observed with scaled images (and
// with non-scaled images, but for a different reason):  Bug 1145

class SubpixelTranslateView : public SampleView {
public:
    SubpixelTranslateView(const char imageFilename[],
                          float horizontalVelocity,
                          float verticalVelocity)
      : fHorizontalVelocity(horizontalVelocity),
        fVerticalVelocity(verticalVelocity) {
      SkString resourcePath = GetResourcePath(imageFilename);
      SkImageDecoder* codec = nullptr;
      SkFILEStream stream(resourcePath.c_str());
      if (stream.isValid()) {
          codec = SkImageDecoder::Factory(&stream);
      }
      if (codec) {
          stream.rewind();
          codec->decode(&stream, &fBM, kN32_SkColorType, SkImageDecoder::kDecodePixels_Mode);
          delete codec;
      } else {
          fBM.allocN32Pixels(1, 1);
          *(fBM.getAddr32(0,0)) = 0xFF0000FF; // red == bad
      }
      fCurPos = SkPoint::Make(0,0);
      fSize = 200;
    }

protected:
    SkBitmap fBM;
    SkScalar fSize;
    float fHorizontalVelocity, fVerticalVelocity;

    SkPoint fCurPos;

    // overrides from SkEventSink
    bool onQuery(SkEvent* evt) override {
        if (SampleCode::TitleQ(*evt)) {
            SampleCode::TitleR(evt, "SubpixelTranslate");
            return true;
        }
        return this->INHERITED::onQuery(evt);
    }

    void onDrawContent(SkCanvas* canvas) override {

        static const SkFilterQuality gQualitys[] = {
            kNone_SkFilterQuality,
            kLow_SkFilterQuality,
            kMedium_SkFilterQuality,
            kHigh_SkFilterQuality
        };

        SkPaint paint;
        paint.setTextSize(48);
        paint.setSubpixelText(true);

        paint.setAntiAlias(true);
        for (size_t i = 0; i < SK_ARRAY_COUNT(gQualitys); ++i) {
            paint.setFilterQuality(gQualitys[i]);
            SkRect r = SkRect::MakeXYWH( fCurPos.fX + i * (fSize + 10), fCurPos.fY, fSize, fSize );
            canvas->drawBitmapRect( fBM, r, &paint );
        }

        canvas->drawText( "AA Scaled", strlen("AA Scaled"), fCurPos.fX + SK_ARRAY_COUNT(gQualitys) * (fSize + 10), fCurPos.fY + fSize/2, paint );

        paint.setAntiAlias(false);
        for (size_t i = 0; i < SK_ARRAY_COUNT(gQualitys); ++i) {
            paint.setFilterQuality(gQualitys[i]);
            SkRect r = SkRect::MakeXYWH( fCurPos.fX + i * (fSize + 10), fCurPos.fY + fSize + 10, fSize, fSize );
            canvas->drawBitmapRect( fBM, r, &paint );
        }
        canvas->drawText( "Scaled", strlen("Scaled"), fCurPos.fX + SK_ARRAY_COUNT(gQualitys) * (fSize + 10), fCurPos.fY + fSize + 10 + fSize/2, paint );

        paint.setAntiAlias(true);
        for (size_t i = 0; i < SK_ARRAY_COUNT(gQualitys); ++i) {
            paint.setFilterQuality(gQualitys[i]);
            canvas->drawBitmap( fBM, fCurPos.fX + i * (fBM.width() + 10), fCurPos.fY + 2*(fSize + 10), &paint );
        }

        canvas->drawText( "AA No Scale", strlen("AA No Scale"), fCurPos.fX + SK_ARRAY_COUNT(gQualitys) * (fBM.width() + 10), fCurPos.fY + 2*(fSize + 10) + fSize/2, paint );

        paint.setAntiAlias(false);
        for (size_t i = 0; i < SK_ARRAY_COUNT(gQualitys); ++i) {
            paint.setFilterQuality(gQualitys[i]);
            canvas->drawBitmap( fBM, fCurPos.fX + i * (fBM.width() + 10), fCurPos.fY + 2*(fSize + 10) + fBM.height() + 10, &paint );
        }

        canvas->drawText( "No Scale", strlen("No Scale"), fCurPos.fX + SK_ARRAY_COUNT(gQualitys) * (fBM.width() + 10), fCurPos.fY + 2*(fSize + 10) + fBM.height() + 10 + fSize/2, paint );


        fCurPos.fX += fHorizontalVelocity;
        fCurPos.fY += fVerticalVelocity;
        this->inval(nullptr);
    }

private:
    typedef SampleView INHERITED;
};

//////////////////////////////////////////////////////////////////////////////

static SkView* MyFactory() { return new SubpixelTranslateView("mandrill_256.png", .05f, .05f); }
static SkViewRegister reg(MyFactory);