从位图在Android的裁剪圆形区域 [英] Cropping circular area from bitmap in Android

问题描述

我有一个位图，我想从这个位图裁剪一个圆形区域。圈以外的所有像素应该是透明的。我怎样才能做到这一点？

I have a bitmap and I want to crop a circular region from this bitmap. All pixels outside the circle should be transparent. How can I do this?

推荐答案

长的头脑风暴后，我已经找到了解决方案

After long brainstorming I have found the solution

public Bitmap getCroppedBitmap(Bitmap bitmap) {
    Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
            bitmap.getHeight(), Config.ARGB_8888);
    Canvas canvas = new Canvas(output);

    final int color = 0xff424242;
    final Paint paint = new Paint();
    final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());

    paint.setAntiAlias(true);
    canvas.drawARGB(0, 0, 0, 0);
    paint.setColor(color);
    // canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
    canvas.drawCircle(bitmap.getWidth() / 2, bitmap.getHeight() / 2,
            bitmap.getWidth() / 2, paint);
    paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
    canvas.drawBitmap(bitmap, rect, rect, paint);
    //Bitmap _bmp = Bitmap.createScaledBitmap(output, 60, 60, false);
    //return _bmp;
    return output;
}

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