ImageView设置成圆形

转发https://blog.youkuaiyun.com/yangyahuiguo/article/details/52253401?utm_source=blogxgwz2
1.中央截取正方形，可设置圆角

        Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.testimg);
        //设置bitmap.getWidth()可以获得圆形
        Bitmap bitmap1 = ClipSquareBitmap(bitmap,200,bitmap.getWidth());
        imageView.setImageBitmap(bitmap1);

    public static Bitmap ClipSquareBitmap(Bitmap bmp, int width, int radius) {
        if (bmp == null || width <= 0)
            return null;
        //如果图片比较小就没必要进行缩放了

        /**
         * 把图片进行缩放，以宽高最小的一边为准，缩放图片比例
         * */
        if (bmp.getWidth() > width && bmp.getHeight() > width) {
            if (bmp.getWidth() > bmp.getHeight()) {
                bmp = Bitmap.createScaledBitmap(bmp, (int) (((float) width) * bmp.getWidth() / bmp.getHeight()), width, false);
            } else {
                bmp = Bitmap.createScaledBitmap(bmp, width, (int) (((float) width) * bmp.getHeight() / bmp.getWidth()), false);
            }

        } else {
            width = bmp.getWidth() > bmp.getHeight() ? bmp.getHeight() : bmp.getWidth();
            Log.d("zeyu","宽" + width + ",w" + bmp.getWidth() + ",h" + bmp.getHeight());
            if (radius > width) {
                radius = width;
            }
        }
        Bitmap output = Bitmap.createBitmap(width, width, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        //设置画笔全透明
        canvas.drawARGB(0, 0, 0, 0);
        Paint paints = new Paint();
        paints.setColor(Color.WHITE);
        paints.setAntiAlias(true);//去锯齿
        paints.setFilterBitmap(true);
        //防抖动
        paints.setDither(true);

        //把图片圆形绘制矩形
        if (radius <= 0)
            canvas.drawRect(new Rect(0, 0, width, width), paints);
        else //绘制圆角
            canvas.drawRoundRect(new RectF(0, 0, width, width), radius, radius, paints);
        // 取两层绘制交集。显示前景色。
        paints.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        Rect rect = new Rect();
        if (bmp.getWidth() >= bmp.getHeight()) {
            rect.set((bmp.getWidth() - width) / 2, 0, (bmp.getWidth() + width) / 2, width);
        } else {
            rect.set(0, (bmp.getHeight() - width) / 2, width, (bmp.getHeight() + width) / 2);
        }
        Rect rect2 = new Rect(0, 0, width, width);
        //第一个rect 针对bmp的绘制区域，rect2表示绘制到上面位置
        canvas.drawBitmap(bmp, rect, rect2, paints);
        bmp.recycle();
        return output;
    }

2.这种方式也可获得圆形，但是不是以中央为圆心切的，图像偏上方

    public static Bitmap circleBitmap(Bitmap source) {

        int width = source.getWidth();
        Bitmap bitmap = Bitmap.createBitmap(width, width, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        canvas.drawCircle(width / 2, width / 2, width / 2, paint);

        //设置图片相交情况下的处理方式
        //setXfermode：设置当绘制的图像出现相交情况时候的处理方式的,它包含的常用模式有：
        //PorterDuff.Mode.SRC_IN 取两层图像交集部分,只显示上层图像
        //PorterDuff.Mode.DST_IN 取两层图像交集部分,只显示下层图像
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));

        canvas.drawBitmap(source, 0, 0, paint);

        return bitmap;
    }