如何向UIImage或UIImageView或UIView添加外部光晕 [英] How do I add an outer glow to a UIImage or UIImageView or UIView

问题描述

我想在 UIImage / 中添加FADED阴影/外部光晕UIImageView / UIView 但我知道没有核心图形。

编辑：
请帮助!!

解决方案

使用Cirrostratus概述的方法，保留缓存的副本，然后应用变换以在拖动时更改图像的大小和/或位置。

（警告，这不是功能/测试的代码，但应该让你开始）

   - （UIImage * ）addGlowToImage：（UIImage *）imageInput; 
 {
 CGRect newSize = imageInput.bounds; 
 CGImageRef theImage = imageInput.CGImage; 
 
 //展开大小以处理glow
 newSize.size.width + = 6.0; 
 newSize.size.height + = 6.0; 
 UIGraphicsBeginImageContext（newSize）; 
 CGContextRef ctx = UIGraphicsGetCurrentContext（）; 
 
 CGContextBeginTransparencyLayerWithRect（ctx，newSize，NULL）; 
 CGContextClearRect（ctx，newSize）; 
 
 //你可以重复这个过程来建立发光。 
 CGContextDrawImage（ctx，newSize，theImage）; 
 CGContextSetAlpha（ctx，0.2）; 
 
 CGContextEndTransparencyLayer（ctx）; 
 
 //将原始图像绘制到上下文中，偏移为居中; 
 CGRect centerRect = inputImage.bounds; 
 centerRect.origin.x + = 3.0; 
 centerRect.origin.y + = 3.0; 
 CGContextDrawImage（ctx，centerRect，theImage）; 
 
 result = UIGraphicsGetImageFromCurrentImageContext（）; 
 UIGraphicsEndImageContext（）; 
 
返回结果;然后在你的方法中缩放，你会做类似于：
  
  //假设UIImage * cachedImage = [self addGlowToImage：origImage];已被调用。 
 //假设存在比例的ivars 
 
 CGRect newRect = cachedImage.bounds; 
 newRect.size.width + = scale; 
 newRect.size.height + = scale; 
 
 [cachedImage drawInRect：newRect]; //图像将缩放以填充目标矩形。 
  
一定要看看苹果文档。良好的起点是 Quartz 2D编程指南。
 
I want to add a FADED shadow/outer glow to a UIImage/UIImageView/UIView but I know no Core Graphics at all.  

Edit:
Please Help!!
解决方案
Take the approach outlined by Cirrostratus, keep a cached copy of it, and then apply a transform to change the size and/or position of the image while dragging.

(warning, this is not functional/tested code, but should get you started)
-(UIImage*)addGlowToImage:(UIImage*)imageInput;
{
    CGRect newSize = imageInput.bounds;
    CGImageRef theImage = imageInput.CGImage;

    // expand the size to handle the "glow"
    newSize.size.width += 6.0;
    newSize.size.height += 6.0;
    UIGraphicsBeginImageContext(newSize);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    CGContextBeginTransparencyLayerWithRect(ctx, newSize, NULL);
    CGContextClearRect(ctx, newSize);

    // you can repeat this process to build glow.
    CGContextDrawImage(ctx, newSize, theImage); 
    CGContextSetAlpha(ctx, 0.2);  

    CGContextEndTransparencyLayer(ctx);

    // draw the original image into the context, offset to be centered;
    CGRect centerRect = inputImage.bounds;
    centerRect.origin.x += 3.0;
    centerRect.origin.y += 3.0;
    CGContextDrawImage(ctx, centerRect, theImage);

    result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return result;
}
Then in your method while scaling you would do something like:
// assumes UIImage *cachedImage = [self addGlowToImage:origImage]; has been called already.
// assumes ivars for scale exists

    CGRect newRect = cachedImage.bounds;
    newRect.size.width += scale;
    newRect.size.height += scale;

    [cachedImage drawInRect:newRect];  // image will be scaled to fill destination rectangle.
Definitely take a look at the apple docs.  A good starting place is the Quartz 2D Programming Guide.

                        
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