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：
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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;
}
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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：
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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;
}
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