一些有关图像处理的代码片段(抓图、倒影、圆角)

捕捉屏幕截图
CALayer实例使用Core Graphics的renderInContext方法可以将视图绘制到图像上下文中以便转化为其他UIImage实例。前提先#import <QuartzCore/QuartzCore.h>

+ (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;}

注：UIGraphicsBeginImageContext(CGSize size)创建一个基于位图的上下文(context)，并将其设置为当前上下文。函数功能与UIGraphicsBeginImageContextWithOptions相同，相当于该方法的opaque参数为NO，scale因子为1.0。而UIGraphicsEndImageContext()方法是移除栈顶的基于当前位图的图形上下文。

 

视图添加倒影效果

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];}

 另一：使用Core Graphics创建倒影

+ (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;}

//Create a shrunken frame for the reflection

+ (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];}

实现圆角图片：

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********/

另有方法可见：http://www.4ucode.com/Study/Topic/2058289转载文章。

实现iPhone图标的水晶立体效果

- (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];}