Is it possible to stroke a CGImageRef using Core Graphics?

I have a CGImageRef to a shape with a transparent background. Is is possible to stroke the image, like you can stroke a path with CGContextStrokePath()? Alternativ开发者_开发知识库ely, can you convert the image to a path and stroke that?

You can use CGContextDrawTiledImage. It's not exactly what you are looking for, but as far as I know there is no built-in way to do what you want. You can use a combination of well-placed rects and clipping paths to achieve the look you are going for, however.

It turns out there's no easy way to do this, so I ended up having to iterate over each pixel (you can get a pointer to the image data using CGBitmapContextGetData()) and adjusting the RGB value of every one that was adjacent to an opaque pixel.