在UIImage周围添加透明空间 [英] Add transparent space around a UIImage

问题描述

假设我们有600X400的图像，我们希望最终得到1000X100的新图像，其中包含中心的初始图像和周围的透明空间。我怎样才能在代码中实现这一目标？

Lets say we have an image of 600X400 and we want to end up with an new image of 1000X100 which contains the initial image in the centre and transparent space around it. How can I achieve that in code?

推荐答案

你创建一个1000x1000的新图像上下文，在中间绘制你的旧图像，然后得到新的来自上下文的 UIImage 。

You create a new image context that is 1000x1000, draw your old image in the middle, then get the new UIImage from the context.

// Setup a new context with the correct size
CGFloat width = 1000;
CGFloat height = 1000;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(width, height), NO, 0.0);        
CGContextRef context = UIGraphicsGetCurrentContext();       
UIGraphicsPushContext(context);                             

// Now we can draw anything we want into this new context.
CGPoint origin = CGPointMake((width - oldImage.size.width) / 2.0f,
                            (height - oldImage.size.height) / 2.0f);
[oldImage drawAtPoint:origin];

// Clean up and get the new image.
UIGraphicsPopContext();                             
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

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