ios界面特效：倒影

///////////////////////////////////ImageHelper.h///////////////////////////////////////////////////#import <Foundation/Foundation.h>#import <UIKit/UIKit.h>#import <QuartzCore/QuartzCore.h> @interface ImageHelper : NSObject   + (void) addReflectionToView: (UIView *) theView;@end///////////////////////////////////ImageHelper.m///////////////////////////////////////////////////      #import "ImageHelper.h"@implementation ImageHelperconst CGFloat kReflectDistance = 10.0f;   //定义倒影与实体的中间间隔 + (void) addReflectionToView: (UIView *) theView   // 外部接口，倒影处理，从这里开始{    theView.clipsToBounds = NO;       UIImageView *reflection = [[UIImageView alloc] initWithImage:[ImageHelper reflectionOfView:theView withPercent: 1]]; // 具体处理    CGRect frame = reflection.frame;    frame.origin = CGPointMake(0.0f, theView.frame.size.height + kReflectDistance);    reflection.frame = frame;    [theView addSubview:reflection];           //将倒影‘贴’在现有视图下方    [reflection release];}//核心函数，cookbook版+ (UIImage *) reflectionOfView: (UIView *)theView withPercent: (CGFloat) percent // percent这个参数用于设置阴影显示多少{       // Retain the width but shrink the height    CGSize size = CGSizeMake(theView.frame.size.width, theView.frame.size.height * percent);       // 制作镜像    UIGraphicsBeginImageContext(size);    CGContextRef context =  UIGraphicsGetCurrentContext();   [theView.layer renderInContext:context];    UIImage *partialimg = UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();       // 添加灰蒙渐变效果    CGImageRef mask = [ImageHelper createGradientImage:size];    CGImageRef ref = CGImageCreateWithMask(partialimg.CGImage, mask);    UIImage *theImage = [UIImage imageWithCGImage:ref];    CGImageRelease(ref);    CGImageRelease(mask);       return theImage;}//核心函数，xes改良版+ (UIImage *) reflectionOfView_2: (UIView *)theView withPercent: (CGFloat) percent{       // Retain the width but shrink the height    CGSize size = CGSizeMake(theView.frame.size.width, theView.frame.size.height * percent);        // 制作镜像    CGContextRef context =  MyCreateBmpContext(size.width,size.height);/     CGFloat height_left= theView.bounds.size.height - size.height;    CGContextTranslateCTM(context, 0, -height_left);    [theView.layer renderInContext:context];    CGImageRef bmpContext = CGBitmapContextCreateImage(context);      // 添加灰蒙渐变效果    CGImageRef mask = [ImageHelper createGradientImage:size];    CGImageRef ref = CGImageCreateWithMask(bmpContext , mask);    UIImage *theImage = [UIImage imageWithCGImage:ref];    CGImageRelease(ref);    CGImageRelease(mask);       return theImage;}CGContextRef MyCreateBmpContext(int pixelsWide, int pixelsHigh){    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();  // create the bitmap context CGContextRef bitmapContext = CGBitmapContextCreate (nil, pixelsWide, pixelsHigh, 8,              0, colorSpace,              // this will give us an optimal BGRA format for the device:              (kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst)); CGColorSpaceRelease(colorSpace);       return bitmapContext;}+ (CGImageRef) createGradientImage: (CGSize)size       //蒙化处理函数{    CGFloat colors[] = {0.0, 1.0, 1.0, 1.0};       // Create gradient in gray device color space    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();    CGContextRef context = CGBitmapContextCreate(nil, size.width, size.height, 8, 0, colorSpace, kCGImageAlphaNone);    CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace, colors, NULL, 2);    CGColorSpaceRelease(colorSpace);       // Draw the linear gradient    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;}

在iphone上经常可以看到图标的倒影效果，看起来挺复杂的，不过网上有很多博客都把cookbook上的代码拷贝了上来，然而经过测试那段代码只能实现一个一模一样的镜像，但不是倒立对称的。

       首先要说的是，cookbook我觉得是故意只给你看一部分的，书上看得到的是一段类方法的函数，其实真正要使用，需要自己做一个类，ImageHelper,然后比如要对myview倒影化处理，只需调用[ImageHelper  reflectToview:myview]即可。