保存图片到本地和相册

1.保存到iOS相册需要引入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.保存图片到本地

-(UIImage *) getImageFromURL:(NSString *)fileURL {
    NSLog(@"执行图片下载函数");
    UIImage * result;
    
    NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
    result = [UIImage imageWithData:data];
    
    return result;
}


-(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    if ([[extension lowercaseString] isEqualToString:@"png"]) {
        [UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];
    } else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {
        [UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];
    } else {
        //ALog(@"Image Save Failed\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);
        NSLog(@"文件后缀不认识");
    }
}

保存
-(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]];
    
    return result;
}

NSString * documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSLog(@"保存路径:%@",documentsDirectoryPath);
    //Get Image From URL
    UIImage * imageFromURL = [self getImageFromURL:@"http://file.duteba.com/phone/2009/04/5/ftGxL8kcUL.jpg"];
    
    //Save Image to Directory
    [self saveImage:imageFromURL withFileName:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];
    
    //Load Image From Directory
    UIImage * imageFromWeb = [self loadImage:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];
    [img setImage:imageFromWeb];
    
    //取得目录下所有文件名
    NSArray *file = [[[NSFileManager alloc] init] subpathsAtPath:documentsDirectoryPath];
    //NSLog(@"%d",[file count]);
    NSLog(@"%@",file);
    显示

NSString *documentsDirectory2 = [path2 objectAtIndex:0]; //path数组里貌似只有一个元素
    //字符串拼接得到文件完整路径
    NSString *filestr = @"/MyImage.jpg";
    NSString *newstr = [documentsDirectory2 stringByAppendingString:filestr];
    NSLog(@"完整路径是:%@",newstr);
    
    NSData *dd = [NSData dataWithContentsOfFile:newstr];
    [img222 setImage:[UIImage imageWithData:dd]];
另外，还可以将图片的路径保存在plist文件里，这样可以避免过多的IO操作。