如何制作一个圆角图像

void

addRoundedRectToPath(CGContextRef
context, CGRect rect, 

float

ovalWidth,

float

ovalHeight);

{

float

fw,
fh;

if

(ovalWidth
== 0 || ovalHeight == 0) {

CGContextAddRect(context,
rect);

return

;

}

CGContextSaveGState(context);

CGContextTranslateCTM
(context, CGRectGetMinX(rect), CGRectGetMinY(rect));

CGContextScaleCTM
(context, ovalWidth, ovalHeight);

fw
= CGRectGetWidth (rect) / ovalWidth;

fh
= CGRectGetHeight (rect) / ovalHeight;

CGContextMoveToPoint(context,
fw, fh/2);

CGContextAddArcToPoint(context,
fw, fh, fw/2, fh, 1);

CGContextAddArcToPoint(context,
0, fh, 0, fh/2, 1);

CGContextAddArcToPoint(context,
0, 0, fw/2, 0, 1);

CGContextAddArcToPoint(context,
fw, 0, fw, fh/2, 1);

CGContextClosePath(context);

CGContextRestoreGState(context);

}

-
(UIImage *)roundCornersOfImage:(UIImage *)source;

{

int

w
= source.size.width;

int

h
= source.size.height;

CGColorSpaceRef
colorSpace = CGColorSpaceCreateDeviceRGB();

CGContextRef
context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);

CGContextBeginPath(context);

CGRect
rect = CGRectMake(0, 0, w, h);

addRoundedRectToPath(context,
rect, 5, 5);

CGContextClosePath(context);

CGContextClip(context);

CGContextDrawImage(context,
CGRectMake(0, 0, w, h), source.CGImage);

CGImageRef
imageMasked = CGBitmapContextCreateImage(context);

CGContextRelease(context);

CGColorSpaceRelease(colorSpace);

return

[UIImage
imageWithCGImage:imageMasked];   

}

//该代码片段来自于: http://www.sharejs.com/codes/objectc/142