Android中使用Bitmap类将矩形图片转为圆形的方法

一般要做正圆形图片，只能是正方形的基础上才能实现，否则就变成椭圆了，下面说说如何使长方形的图片生成正圆形图片
废话不多说，没图没真相，先上图吧：
原图：

变成正圆后：

下面上代码：

public static 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;
 }
 ZLog.i(TAG, "ps:"+ left +", "+ top +", "+ right +", "+ bottom);

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;
}

下面再解释下：
由于图片是长方形，所以图片的 宽、高 肯定会有一边要小于另一边，要生成正方形就已最小的一边为基准，再来裁切定位另一边的显示范围
至于圆角的半径则是正方形宽的一半，用过 CSS 的就知道，画圆很方便 border-radius设为 50％ 就可以了，都是一个道理
android 的 UI 真是太繁琐了

矩形画个圆角的代码：

public static Bitmap makeRoundCorner(Bitmap bitmap, int px)
{
 int width = bitmap.getWidth();
 int height = bitmap.getHeight();
 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(0, 0, width, height);
 RectF rectF = new RectF(rect);
 paint.setAntiAlias(true);
 canvas.drawARGB(0, 0, 0, 0);
 paint.setColor(color);
 canvas.drawRoundRect(rectF, px, px, paint);
 paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
 canvas.drawBitmap(bitmap, rect, rect, paint);
 return output;
}