iPhone开发：UIImage的一系列操作

1.Combine two UIImages－合成

To add two UIImages together you need to make use of Graphics Context.

- (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {  

    UIGraphicsBeginImageContext(image1.size);  

    // Draw image1  

    [image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];  

    // Draw image2  

    [image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];  

    UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();  

    UIGraphicsEndImageContext();  

    return resultingImage;  

}

 

2.Create a UIImage from a part of another UIImage－截取

This requires a round-trip to Core Graphics land:

- (UIImage *)imageFromImage:(UIImage *)image inRect:(CGRect)rect {  

    CGImageRef sourceImageRef = [image CGImage];  

    CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, rect);  

    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];  

    return newImage;  

} 

 

3.Save UIImage to Photo Album－保存到相册

This is just a one-liner:

 

UIImageWriteToSavedPhotosAlbum(image, self, @selector(imageSavedToPhotosAlbum: didFinishSavingWithError: contextInfo:), context);

And to know if the save was successful:

- (void)imageSavedToPhotosAlbum:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {  

    NSString *message;  

    NSString *title;  

    if (!error) {  

        title = NSLocalizedString(@"SaveSuccessTitle", @"");  

        message = NSLocalizedString(@"SaveSuccessMessage", @"");  

    } else {  

        title = NSLocalizedString(@"SaveFailedTitle", @"");  

        message = [error description];  

    }  

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title  

                                                    message:message  

                                                   delegate:nil  

                                          cancelButtonTitle:NSLocalizedString(@"ButtonOK", @"")  

                                          otherButtonTitles:nil];  

    [alert show];  

    [alert release];  

}