Compare 2 images directly I would like to compare 2 images with little color changes to another. (To be specific, the raw render result and the output of my compositing viewer-node). 

For now, i use two UV/Image Editor windows, displaying my two images. The problem now is that i need to resize/move both images so that the edge is fitting correctly (wich is unpleasent work). Also, when moving the border around, both images also move a bit...



Is there a better method to display two images on top of each other with a movable border between them?
In the compositor you can use the split viewer node.



From the manual:


  The SplitViewer node takes two images and displays one-half of each on each side (top socket on the right half, bottom socket input on the left). Use this node for making side-by-side comparisons of two renderings/images, perhaps from different render layers or from different scenes. When transitioning between scenes, you want to be sure the stop action is seamless; use this node to compare the end of one scene with the beginning of another to ensure they align.