一些有关图像处理的代码片段(抓图、倒影、圆角)http://www.189works.com/article-41036-1.html

+ (UIImage *) imageFromView: (UIView *)theView {
// draw a view's contents into an image context
UIGraphicsBeginImageContext(theView.frame.size);
CGContextRef  context = UIGraphicsGetCurrentContext();

[theView.layer  renderInContext:context];
UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return theImage;
}

const CGFloat kReflectPercent = -0.25f;
const CGFloat kReflectOpacity = 0.3f;
const CGFloat kReflectDistance = 10.0f;

+ (void)addSimpleReflectionToView:(UIView *)theView
{
CALayer *reflectionLayer = [CALayer layer];
reflectionLayer.contents = [theView layer].contents;
reflectionLayer.opacity = kReflectOpacity;
reflectionLayer.frame = CGRectMake(0.0f,0.0f,theView.frame.size.width,theView.frame.size.height*kReflectPercent);  //倒影层框架设置，其中高度是原视图的百分比
CATransform3D stransform = CATransform3DMakeScale(1.0f,-1.0f,1.0f);
CATransform3D transform = CATransform3DTranslate(stransform,0.0f,-(kReflectDistance + theView.frame.size.height),0.0f);
reflectionLayer.transform = transform;
reflectionLayer.sublayerTransform = reflectionLayer.transform;
[[theView layer] addSublayer:reflectionLayer];
}

+ (CGImageRef) createGradientImage:(CGSize)size
{
CGFloat colors[] = {0.0,1.0,1.0,1.0};
//在灰色设备色彩上建立一渐变
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
CGContextRef context = CGBitmapContextCreate(nil,size.width,size.height,8,0,colorSpace,kCGImageAlphaNone);
CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace,colors,NULL,2);
CGColorSpaceRelease(colorSpace);

//绘制线性渐变
CGPoint p1 = CGPointZero;
CGPoint p2 = CGPointMake(0,size.height);
CGContextDrawLinearGradient(context,gradient,p1,p2,kCGGradientDrawsAfterEndLocation);

//Return the CGImage
CGImageRef theCGImage = CGBitmapContextCreateImage(context);
CFRelease(gradient);
CGContextRelease(context);
return theCGImage;
}

+ (UIImage *) reflectionOfView:(UIView *)theView WithPercent:(CGFloat) percent
{
//Retain the width but shrink the height
CGSize size = CGSizeMake(theView.frame.size.width, theView.frame.size.height * percent);

//Shrink the View
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
[theView.layer renderInContext:context];
UIImage *partialimg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

//build the mask
CGImageRef mask = [ImageHelper createGradientImage:size];
CGImageRef ref = CGImageCreateWithMask(partialimg.CGImage,mask);
UIImage *theImage = [UIImage imageWithCGImage:ref];
CGImageRelease(ref);
CGImageRelease(mask);
return theImage;
}

const CGFloat kReflectDistance = 10.0f;
+ (void) addReflectionToView: (UIView *)theView
{
theView.clipsToBounds = NO;
UIImageView *reflection = [[UIImageView alloc] initWithImage:[ImageHelper reflectionOfView:theView withPercent:0.45f]];
CGRect frame = reflection.frame;
frame.origin = CGPointMake(0.0f, theView.frame.size.height + kReflectDistance);
reflection.frame = frame;

// add the reflection as a simple subview
[theView addSubView:reflection];
[reflection release];
}

UIColor *color = [UIColor colorWithRed:0.95 green:0.95 blue:0.95 alpha:0];
[aImage setBackgroundColor:color]; //设置背景透明

/******设置图片圆角begin*******/
aImage.layer.masksToBounds = YES;
aImage.layer.cornerRadius = 5.0;
aImage.layer.borderWidth = 0.5;
aImage.layer.borderColor = [[UIColor grayColor] CGColor];
/******设置图片圆角end********/

- (void)viewDidLoad {
[super viewDidLoad];
UIGraphicsBeginImageContext(icon.bounds.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
const CGFloat components[4] = {0.0,0.4,0.0,1.0};
CGContextSetFillColor(ctx, components);
CGContextFillRect(ctx, CGRectMake(0, 0, icon.bounds.size.width, icon.bounds.size.height));
UIImage *background = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImage *image = [UIImage imageNamed:@"icon.png"];
UIImage *mask = [UIImage imageNamed:@"IconBase.png"];
UIImage *roundCorner = [UIImage imageNamed:@"round-corner.png"];
icon.image = image;
CALayer* subLayer = [[CALayer layer] retain];
subLayer.frame = icon.bounds;
subLayer.contents = (id)[background CGImage];
CALayer* maskLayer = [[CALayer layer] retain];
maskLayer.frame = icon.bounds;
maskLayer.contents = (id)[mask CGImage];
[subLayer setMask:maskLayer];
[[icon layer] addSublayer:subLayer];
CALayer* roundCornerLayer = [[CALayer layer] retain];
roundCornerLayer.frame = icon.bounds;
roundCornerLayer.contents = (id)[roundCorner CGImage];
[[icon layer] setMask:roundCornerLayer];
[maskLayer release];
[subLayer release];
[roundCornerLayer release];
}