When the images are overlaid, the relative intensity of the images (alpha blend) is controlled by a slider control at the left side.You can click anywhere in the slider to set the blend directly, or you can drag the slider to change the blend interactively. The button above the slider toggles between 0% and 100% blends, and if you double click the button, the blend toggles automatically every second until you click the button again.This can be useful when looking for multiple small changes.
You can also pan the image simply by left-dragging it.The context menu there allows you to compare them using from the context menu.If you want to see the difference between the last committed revision and your working copy, assuming that the working copy hasn't been modified, just right click on the file. This will perform a diff between the revision before the last-commit-date (as recorded in your working copy) and the working BASE.Note that a simple text search is used, so if you want to restrict the list to C source files you should enter There are many tools available for diffing text files, including our own Tortoise Merge, but we often find ourselves wanting to see how an image file has changed too. for any of the common image file formats will start Tortoise IDiff to show image differences.By default the images are displayed side-by-side but you can use the View menu or toolbar to switch to a top-bottom view instead, or if you prefer, you can overlay the images and pretend you are using a lightbox.
If you select the option, then the pan controls (scrollbars, mousewheel) on both images are linked.