使用图像的自定义进度条

Question

我正在使用自定义进度条来显示基于百分比值的图像的一部分。我的想法是有两个图像，原始版本和版本。我正在显示b & w，并且基于原始图像的百分比来裁剪。工作很好，但从上到下。

我想问一下，有什么办法可以让原始图像从下到上“成长”？

下面是我的代码示例到现在为止：

UIImageView *imgDefViewGray = [[UIImageView alloc] initWithFrame:CGRectMake(170, 85, 60, 60)]; 
    imgDefViewGray.image = [UIImage imageNamed:@"castle-gray.png"]; 
    [self addSubview:imgDefViewGray]; 

    UIImageView *imgDefView = [[UIImageView alloc] initWithFrame:CGRectMake(170, 85, 60, 60)]; 
    imgDefView.image = [UIImage imageNamed:@"castle.png"]; 

    CGRect rect = CGRectMake(0, 0 , 60, **50**); 
    CGImageRef imageRef = CGImageCreateWithImageInRect([imgDefView.image CGImage], rect); 
    UIImage *img = [UIImage imageWithCGImage:imageRef]; 

    imgDefView = [[UIImageView alloc] initWithFrame:CGRectMake(170, 85, 60, **50**)]; 
    imgDefView.image = img; 
    [self addSubview:imgDefView]; 

因此，通过改变大胆（双星号）的价值，我已经实现了裁剪的原始图像，就像我想，但方向顶部 - >底部。我希望它底部 - >顶部。

在此先感谢

Answer 1

多次尝试之后，我想通了，得到我想要的结果。以下是我解决我的问题的方法。我希望将来有谁会面对或想要同样的事物会发现它有用。

UIImageView *imgDefViewGray = [[UIImageView alloc] initWithFrame:CGRectMake(170, 85, 60, 60)]; 
    imgDefViewGray.image = [UIImage imageNamed:@"castle-gray.png"];//60x60 b&w image 

    UIImage originalImg = [UIImage imageNamed:@"castle.png"];//60x60 original image 
    CGRect rect = CGRectMake(0, originalImg.size.height-scaleDefence), 60 , scaleDefence);//scaleDefence is just a float variable that converts current percentage value to px. 

    CGImageRef imageRef = CGImageCreateWithImageInRect([originalImg CGImage], rect); 
    UIImage *croppedImg = [UIImage imageWithCGImage:imageRef]; 

    UIImageView *imgDefView = [[UIImageView alloc] initWithFrame:CGRectMake(0, originalImg.size.height-scaleDefence, 60, scaleDefence)];//dynamically changing y-axis depending on cropped image's height. 
    imgDefView.image = croppedImg; 

    [imgDefViewGray addSubview:imgDefView];//make original image part of b&w 
    [self addSubview:imgDefViewGray];//finally add the result to the view