CGImageRef 和绘图层
我有这样的代码：
CGDataProviderRef provider = CGDataProviderCreateWithFilename([myFile UTF8String]);
CGImageRef img = CGImageCreateWithJPEGDataProvider(provider, NULL, true, kCGRenderingIntentDefault);
稍后我以这种方式在 UIImage 中加载 CGImageRef：
UIImage *uiImage = [[UIImage alloc] initWithCGImage:destImage];
我想在该图像上画一个圆圈。关键是圆圈移动了，所以必须删除并重新绘制。我想实现这一点的最佳方法是使用图层，所以我的问题是：如何向该代码添加一个图层并在其上画一个圆圈？我稍后如何重置图层并重新绘制该圆圈？
谢谢你！
I have this code:
CGDataProviderRef provider = CGDataProviderCreateWithFilename([myFile UTF8String]);
CGImageRef img = CGImageCreateWithJPEGDataProvider(provider, NULL, true, kCGRenderingIntentDefault);
Later I load that CGImageRef in a UIImage this way:
UIImage *uiImage = [[UIImage alloc] initWithCGImage:destImage];
I'd like to draw a circle over that Image. The point is the circle moves so it has to be deleted and redraw. I guess the best way of accomplishing this is with layers so my question is: How can I add a layer to that code and draw a circle on it? How can I later reset the layer and redraw that circle?
Thank you!
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您将需要使用 UIImageView，然后向该视图添加单独的图层。如果你的图层[圆]移动了，只需将其位置属性设置为新的中心即可；视图系统将负责重新组合所有内容。
要让您的圆圈显示在图层中，您可以使用固定图像、子类 CALayer 并重写drawInContext:，或者设置委托并实现drawLayer:inContext:。
You'll want to use a UIImageView, and then add a separate layer to that view. If your layer [circle] moves, just set its position property to the new center; the view system will take care of re-compositing everything.
To get your circle to show up in the layer, you can either use a fixed image, subclass CALayer and override drawInContext:, or set the delegate and implement drawLayer:inContext:.