问优化iPad 3的图像绘制

EN

   UIImage *mask = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle]pathForResource:@"3.0-Carousel-Ref-Mask.jpg" ofType:nil]];
    //
    UIImage *image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle]pathForResource:self.name ofType: nil]];
    UIGraphicsBeginImageContextWithOptions(mask.size, NO, [[UIScreen mainScreen]scale]);
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(ctx, 0.0, mask.size.height);
    CGContextScaleCTM(ctx, 1.f, -1.f);

    [image drawInRect:CGRectMake(0.f, -mask.size.height, image.size.width, image.size.height)];
    UIImage *flippedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    CGImageRef maskRef = mask.CGImage;
    CGImageRef maskCreate = CGImageMaskCreate(CGImageGetWidth(maskRef),
                                              CGImageGetHeight(maskRef),
                                              CGImageGetBitsPerComponent(maskRef),
                                              CGImageGetBitsPerPixel(maskRef),
                                              CGImageGetBytesPerRow(maskRef),
                                              CGImageGetDataProvider(maskRef), NULL, false);
    CGImageRef masked = CGImageCreateWithMask([flippedImage CGImage], maskCreate);

    CGImageRelease(maskCreate);

    UIImage *maskedImage = [UIImage imageWithCGImage:masked scale:[[UIScreen mainScreen]scale] orientation:UIImageOrientationUp];
    CGImageRelease(masked);


    if (maskedImage) {
        [mainView performSelectorOnMainThread:@selector(imageDidLoad:)
                                             withObject:[NSArray arrayWithObjects:maskedImage, endView, nil]
                                          waitUntilDone:YES];
    } else
        NSLog(@"Unable to find sample image: %@", self.name);