将图片保存成png 或者jpg格式

-(void)saveImage:(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]);
    
}