将UIImage保存到iOS照片库和对应程序沙盒中

1.保存到iOS照片库需要引入QuartzCore.framework框架，具体代码如下：
.h文件
#import <QuartzCore/QuartzCore.h>
UIImageView *imageView;
@property (nonatomic, retain) IBOutlet UIImageView *imageView;
.m文件
UIGraphicsBeginImageContext(imageView.bounds.size);
[imageView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *temp = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(temp, nil, nil, nil);

2.保存到对应的沙盒目录中，具体代码如下：
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"sms.gif"]];   // 保存文件的名称
BOOL result = [UIImagePNGRepresentation(imageView.image)writeToFile: filePath    atomically:YES]; // 保存成功会返回YES