UIImageView curl shadow effect using shadowPath

In my last post I discussed how to display UIImageView with border and shadow. One important thing to consider while displaying shadow is performance. This can be improved by explicitly specifying shadow path property in CALayer class. According to iOS CALayer class reference documentation "Specifying an explicit path usually improves rendering performance".  If shadowPath property is not defined then the shadow is created using layers composited alpha channel. In this post we will see how to create curl shadow effect using shadowPath property. The output of our image will look like as shown in figure 1.

Figure1: (a) original photo (b) photo with border and curl shadow