Bitmap-把方形图片处理为圆形

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;


 protected Bitmap makeRoundCorner(Bitmap bitmap) {
        int width = bitmap.getWidth();
        int height = bitmap.getHeight();
        int left = 0, top = 0, right = width, bottom = height;
        float roundPx = height / 2; 
        if (width > height) {
            left = (width - height) / 2; 
            top = 0; 
            right = left + height;
            bottom = height;
        } else if (height > width) {
            left = 0; 
            top = (height - width) / 2; 
            right = width;
            bottom = top + width;
            roundPx = width / 2; 
        }    

        Bitmap output = Bitmap.createBitmap(width, height,
                Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        int color = 0xff424242;
        Paint paint = new Paint();
        Rect rect = new Rect(left, top, right, bottom);
        RectF rectF = new RectF(rect);

        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;
    }