如何在iphone上的新UIImage上渲染径向渐变 [英] How to render a radial gradient onto a new UIImage on an iphone

问题描述

只是想知道如何将径向渐变（点>圆）渲染到新的UIImage（iphone）上。
我看到以下内容：

Just wondering how to render a radial gradient (point > circle) onto a new UIImage (iphone). I saw the following:

http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_shadings/dq_shadings.html

它让我觉得我需要使用CGShadingRef或CGGradientRef，并使用UIImage的'imageWithCGImage'构造函数从CG *转到UIImage ...但我无法弄清楚如何。

And it made me think i need to use CGShadingRef or CGGradientRef, and use UIImage's 'imageWithCGImage' constructor to go from the CG* to a UIImage... but i can't figure out how.

任何建议都非常感谢！

推荐答案

你应该阅读关于图形上下文与您链接的部分相同的文档。所有绘图都在图形上下文中进行。如果要创建具有径向渐变或线性渐变或其他任何内容的图像，则需要：

You should read about Graphics Contexts in the same document as the section you linked. All drawing happens in a graphics context. If you want to create an image that has a radial gradient, or a linear gradient, or anything else, you'll need to:

• 使用 UIGraphicsBeginImageContextWithOptions 。


• 执行您想要在图像中显示的任何图形。


• 致电 UIGraphicsGetImageFromCurrentImageContext 从上下文中获取图像。这给你一个UIImage，所以不需要从CGImage转换。


• Call UIGraphicsEndImageContext 来清理上下文。

• Create a graphics context for your image with UIGraphicsBeginImageContextWithOptions.
• Do whatever drawing you want to appear in the image.
• Call UIGraphicsGetImageFromCurrentImageContext to get the image from the context. This gives you a UIImage, so no need to convert from a CGImage.
• Call UIGraphicsEndImageContext to clean up the context.

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