如何在drawRect中为用CGContextDrawPath等绘制的路径设置动画填充颜色？

我想知道是否可以对使用CoreGraphics绘制的路径的填充颜色进行动画处理？
我正在绘制：
使用Quartz进行简单绘制-核心图形

I wonder if is possible to animate the fill color of a path I have drawn using CoreGraphics? I am drawing this: Simple drawing with Quartz - Core Graphics

，我想将其填充颜色从白色更改为灰色。
这可能吗？

and I want to change its fill color from white to let's say gray. Is this possible?

我知道view.layer.content属性的存在，但这在这里有用吗？不过，我不确定在这种情况下如何使用它。

I know the existence of view.layer.content property but Is this useful here? Though, I am not sure how can I use it in this case.

预先感谢。

更新

我正在尝试这种方法（因为它有故障，所以我可以判断它是否可以正常工作）
CGImageRef并使用UIView动画将其传递给self.layer.contents，这是可动画的
，但是....除了没有动画之外，我得到的结果很奇怪。

I am trying this approach (its buggy, hence I can tell if its going to work) basically I am creating a CGImageRef and pass it to self.layer.contents which is animatable using UIView animations but .... I am getting strange results, besides is not animating.

int bitsPerComponent = 8;
int channels = 4;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *data = malloc(self.bounds.size.width*self.bounds.size.height*channels);

CGContextRef context = CGBitmapContextCreate(data,                      //pointer to data
                                             self.bounds.size.width,    //width
                                             self.bounds.size.height,   //height
                                             bitsPerComponent,          //bitsPerComponent
                                             self.bounds.size.width*channels,//bytesPerRow
                                             colorSpace,                    //colorSpace
                                             kCGImageAlphaPremultipliedFirst);  //bitmapInfo

//method that uses below link's code
[self _drawBackgroundInContext:context color:UIColorFromMandalaBoxType(type)];

CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL,         //info, NULL
                                                              data,         //pointer to data
                                                              self.bounds.size.width*self.bounds.size.height*channels, //number of bytes
                                                              NULL);        //release callback


CGImageRef image = CGImageCreate(self.bounds.size.width,            //width
                                 self.bounds.size.height,         //height
                                 bitsPerComponent,                //bitsPerComponent
                                 bitsPerComponent*channels,       //bitsPerPixel
                                 self.bounds.size.width*channels, //bytesPerRow
                                 colorSpace,                        //colorSpace
                                 kCGImageAlphaPremultipliedFirst,   //bitmapInfo
                                 dataProvider, NULL, false, kCGRenderingIntentDefault);

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:1.5f];
self.layer.contents = (id)image;
[UIView commitAnimations];

CGImageRelease(image);
CGDataProviderRelease(dataProvider);
CGContextRelease(context);
free(data);
CGColorSpaceRelease(colorSpace);

逻辑还可以吗？这里的错误在哪里？ ;（

Is logic OK?, and where is the mistake here? ;(