Android - 使用画布在位图之外设置具有背景颜色的图像叠加层

Question

我正在制作相机活动叠加层，我已经成功地在矩形之外创建了不透明的颜色（不透明的黑色）。而且我还成功地在大矩形内创建了一个小矩形。请看下图。如您所见，小矩形上有蓝色背景。问题是，我想在图像（位图）之外制作蓝色背景，而不是覆盖图像。问题是，如果我用透明填充更改图像，蓝色背景将覆盖它。如何使蓝色背景仅覆盖图像的外部？我已经尝试从谷歌找到所有可能的答案，但我没有运气，也许我开始的方法不对，需要建议。

这是我的代码

bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
    Canvas osCanvas = new Canvas(bitmap);

    RectF outerRectangle = new RectF(0, 0, getWidth(), getHeight());

    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(getResources().getColor(R.color.opaque_black));
    paint.setAlpha(99);
    osCanvas.drawRect(outerRectangle, paint);


    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT));

    paint.setColor(Color.TRANSPARENT);
    paint.setStyle(Paint.Style.FILL);
    RectF r1 = new RectF(
            (float) (xStartingPoint),
            (float) (yStartingPoint),
            (float) (parentWidth),
            (float) (parentHeight));

    osCanvas.drawRoundRect(r1, (float) (cornerRadiusRatio * parentHeight),
            (float) (cornerRadiusRatio * parentHeight), paint);

    paint.setStrokeWidth(strokeWidth);
    paint.setColor(getResources().getColor(R.color.colorDeepSky));
    paint.setStyle(Paint.Style.STROKE);

    RectF r2 = new RectF(
            (float) (xStartingPoint),
            (float) (yStartingPoint),
            (float) (parentWidth),
            (float) (parentHeight));

    osCanvas.drawRoundRect(r2, (float) (cornerRadiusRatio * parentHeight),
            (float) (cornerRadiusRatio * parentHeight), paint);

    if (callbackMsg.equals(AppConstant.KTP_SELF)) {
        paint.setColor(getResources().getColor(R.color.colorDeepSky));

        drawRect(osCanvas, paint,
                (float) (xChildStartingPoint),
                (float) (yChildStartingPoint),
                (float) (childWidth + xChildStartingPoint + 0.3 * childWidth),
                (float) (childHeight + 0.7 * yChildStartingPoint));
    }

    RectF outerRectangle2 = new RectF(
    (float) xChildStartingPoint,
    (float) yChildStartingPoint,
    (float) (childWidth + xChildStartingPoint + 0.3 * childWidth),
    (float) (childHeight + 0.7 * yChildStartingPoint));

    Paint paint2 = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint2.setColor(getResources().getColor(R.color.blue));
    paint2.setAlpha(99);
    osCanvas.drawRect(outerRectangle2, paint2);

    Rect r3 = new Rect(
            (int) (xChildStartingPoint),
            (int) (yChildStartingPoint),
            (int) (childWidth + xChildStartingPoint + 0.3 * childWidth),
            (int) (childHeight + 0.7 * yChildStartingPoint));

    paint2 = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint2.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT));
    paint2.setColor(Color.TRANSPARENT);
    paint2.setStyle(Paint.Style.FILL);
    Bitmap mbitmap = BitmapFactory.decodeResource(getResources(),R.drawable.icon_profile2);
    osCanvas.drawBitmap(mbitmap, null, r3, paint2);

谢谢

Answer 1

好的，找到答案了

我正在使用PorterDuff 和DST_OUT 模式

注意： 如果要使图像背景透明并用颜色填充外部区域，请使用 DST_OUT 如果要使外部区域充满颜色，请使用 DST_IN

这是代码，我使用的是 Kotlin

    var paint2 = Paint(Paint.ANTI_ALIAS_FLAG)
        paint2.color = resources.getColor(R.color.opaque_black)
        osCanvas.drawRect(outerRectangle2, paint2)

        paint2 = Paint(Paint.ANTI_ALIAS_FLAG)
        val r3 = Rect(
                xChildStartingPoint.toInt(),
                yChildStartingPoint.toInt(),
                (childWidth + xChildStartingPoint + 0.3 * childWidth).toInt(),
                (childHeight + 0.7 * yChildStartingPoint).toInt())

        paint2.xfermode = PorterDuffXfermode(PorterDuff.Mode.DST_IN)
        val mBitmap = BitmapFactory.decodeResource(resources, R.drawable.selfie_outline)
        osCanvas.drawBitmap(mBitmap, null, r3, paint2)