Android长方形图片生成正圆形，以及矩形图片生成圆角

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;}