Android 截取圆形图片核心代码

原文地址：http://www.eoeandroid.com/forum.php?mod=viewthread&tid=103093

核心代码：

        Bitmap sourceBitmap = BitmapFactory.decodeResource(getResources(),
                R.drawable.xiaohuai);
        //此处要求图片宽值<长度值
        int targetWidth = sourceBitmap.getWidth();
        int targetHeight = targetWidth;
        Bitmap targetBitmap = Bitmap.createBitmap(targetWidth, targetHeight,
                Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(targetBitmap);
        //抗锯齿
        canvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG
                | Paint.FILTER_BITMAP_FLAG));
        Path path = new Path();
        path.addCircle(((float) targetWidth - 1) / 2,
                ((float) targetHeight - 1) / 2,
                (Math.min(((float) targetWidth), ((float) targetHeight)) / 2),
                Path.Direction.CCW);
        canvas.clipPath(path);

        canvas.drawBitmap(sourceBitmap, new Rect(0, 0, sourceBitmap.getWidth(),
                sourceBitmap.getHeight()), new Rect(0, 0, targetWidth,
                targetHeight), null);
        ImageView imageView = (ImageView) findViewById(R.id.my_image_view);
        imageView.setImageBitmap(targetBitmap);

下面的代码更好，感谢同事的贡献

注：保存Bitmap时须保存成PNG格式的，JPG不支持透明

/**
     * 将圆形图片,返回Bitmap
     * @param bitmap 源Bitmap
     * @return
     */
    public static Bitmap getCircleBitmap(Bitmap bitmap) {
        int x = bitmap.getWidth();
        int y = bitmap.getHeight();
        Bitmap output = Bitmap.createBitmap(x,
                y, Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
 
        final int color = 0xff424242;
        final Paint paint = new Paint();
        // 根据原来图片大小画一个矩形
        final Rect rect = new Rect(0, 0, x, y);
        paint.setAntiAlias(true);
        paint.setColor(color);
        // 画出一个圆
        canvas.drawCircle(x/2, x/2, x/2-5, paint);
        //canvas.translate(-25, -6);
        // 取两层绘制交集,显示上层
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        
        // 将图片画上去
        canvas.drawBitmap(bitmap, rect, rect, paint);
        // 返回Bitmap对象
        return output;
    }