void draw(SkCanvas* canvas) {

    SkPaint pRed;

    pRed.setColor(SK_ColorRED);

​

    SkPaint pSolidBlue;

    pSolidBlue.setColor(SK_ColorBLUE);

​

    SkPaint pThirtyBlue;

    pThirtyBlue.setColor(SK_ColorBLUE);

    pThirtyBlue.setAlphaf(0.3);

​

    SkPaint alpha;

    alpha.setAlphaf(0.3);

    // Draw 4 solid red rectangles on the 0th layer.

    canvas->drawRect(SkRect::MakeLTRB(10, 10, 60, 60), pRed);

    canvas->drawRect(SkRect::MakeLTRB(150, 10, 200, 60), pRed);

    canvas->drawRect(SkRect::MakeLTRB(10, 70, 60, 120), pRed);

    canvas->drawRect(SkRect::MakeLTRB(150, 70, 200, 120), pRed);

​

    // Draw 2 blue rectangles that overlap. One is solid, the other

    // is 30% transparent. We should see purple from the right one,

    // the left one overlaps the red because it is opaque.

    canvas->drawRect(SkRect::MakeLTRB(30, 10, 80, 60), pSolidBlue);

    canvas->drawRect(SkRect::MakeLTRB(170, 10, 220, 60), pThirtyBlue);

​

    // Save a new layer. When the 1st layer gets merged onto the

    // 0th layer (i.e. when restore() is called), it will use the provided

    // paint to do so. The provided paint is set to have 30% opacity, but

    // it could also have things set like blend modes or image filters.

    canvas->saveLayer(nullptr, &alpha);

​

    // Draw the same blue overlapping rectangles as before. Notice in the

    // final output, we have two different shades of purple instead of the

    // solid blue overwriting the red. This proves the opacity was applied.

    canvas->drawRect(SkRect::MakeLTRB(30, 70, 80, 120), pSolidBlue);

    canvas->drawRect(SkRect::MakeLTRB(170, 70, 220, 120), pThirtyBlue);

​

    // We draw two more sets of overlapping red and blue rectangles. Notice

    // the solid blue overwrites the red. This proves that the opacity from

    // the alpha paint isn't available when the drawing happens - it only

    // matters when restore() is called.

    canvas->drawRect(SkRect::MakeLTRB(10, 130, 60, 180), pRed);

    canvas->drawRect(SkRect::MakeLTRB(30, 130, 80, 180), pSolidBlue);

​

    canvas->drawRect(SkRect::MakeLTRB(150, 130, 200, 180), pRed);

    canvas->drawRect(SkRect::MakeLTRB(170, 130, 220, 180), pThirtyBlue);

​

    canvas->restore();

}