小编vla*_*r z的帖子

这正是它所需要的,除了它需要大约400毫秒,这是350毫秒太多:

 - (void) updateCompositeImage { //blends together the background and the sprites
    UIGraphicsBeginImageContext(CGSizeMake(480, 320));

    [bgImageView.image drawInRect:CGRectMake(0, 0, 480, 320)];

    for (int i=0;i<numSprites;i++) {
        [spriteImage[spriteType[i]] drawInRect:spriteRect[i] blendMode:kCGBlendModeScreen alpha:spriteAlpha[i]];
    }

    compositeImageView.image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
}

图像相当小,只有三个(for循环只迭代两次)

有没有办法更快地做到这一点？虽然仍然可以使用kCGBlendModeScreen和alpha？