title: Implementing different PorterDuff modes in android
body: <p>I am working on a picture editing tool in which I need to merge two images. Most of the image editing tools like gimp use <b>PorterDuff modes</b> for merging or blending images. I am also using the same approach in android.<br> As android provides limited number of PorterDuff modes, I am not able to achieve the desired result. So, I am thinking of implementing PorterDuff modes(Overlapping, Hard-Light, Soft-Light, Color-burn, Color-dodge) which are not included in android. <br>The problem is I don't know where to start. So, any reference or guidance in this regard will be highly appreciated.</p>