使用Cocoa将阴影添加到PNG [英] Add drop shadow to PNG using Cocoa

问题描述

我有一些透明背景的PNG，我想以编程方式添加阴影。我已经看到了为方形物体添加阴影的例子，但没有看到任何复杂的形状。

I have some PNGs with transparent backgrounds that I would like to add shadows to programatically. I've seen examples of adding shadows to square objects, but haven't seen any with complex shapes.

所以我认为我必须做的两个步骤be：

So the two steps I think I'd have to do would be:

• 隔离PNG形状


• 在PNG后面绘制一个模糊，褪色的形状和偏移。

我在Cocoa中绘制的经验不多，所以对于从哪里开始的任何见解都将非常感激！

I don't have much experience with drawing within Cocoa, so any insight on where to begin would be much appreciated!

屏幕截图：
alt http://www.iworkinprogress.com/images/pngExample.png

推荐答案

最简单的方式是打电话在绘制图像之前， CGContextSetShadow 在 drawRect：中。

Simplest way is to call CGContextSetShadow in your drawRect: before you draw the images.

- (void)drawRect:(CGRect)invalidRect
{
    CGContextRef c = UIGraphicsGetCurrentContext();
    CGContextSetShadow(c, CGSizeMake(5.0f, 5.0f), 5.0f);
    [myImage drawAtPoint:CGPointMake(50.0f, 50.0f)];
}

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