将UIImage保存成JPG或PNG格式存储在本地

 -(void)pngAndJpg:(UIImage*)image{
     NSString  *pngPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Test.png"];
     NSString  *jpgPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Test.jpg"];

     // Write a UIImage to JPEG with minimum compression (best quality)
     // The value 'image' must be a UIImage object
     // The value '1.0' represents image compression quality as value from 0.0 to 1.0
     [UIImageJPEGRepresentation(image, 1.0) writeToFile:jpgPath atomically:YES];

     // Write image to PNG
     [UIImagePNGRepresentation(image) writeToFile:pngPath atomically:YES];

     // Let's check to see if files were successfully written...

     // Create file manager
     NSError *error;
     NSFileManager *fileMgr = [NSFileManager defaultManager];

     // Point to Document directory
     NSString *documentsDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];

     // Write out the contents of home directory to console
     NSLog(@"Documents directory: %@", [fileMgr contentsOfDirectoryAtPath:documentsDirectory error:&error]);

 }