Digital pictures are like any other digital file. The image is made up from millions of small bits of data. You can edit, alter or change a digital picture in ways you couldn't with traditional photography. Using a photo editing program, you can make a person appear thinner in a digital picture by altering the data that creates the picture. Not all programs give you this option; advanced editors like Paint.net, GIMP or Adobe Photoshop contain effects and tools where this type of editing can be accomplished.
Open one of the three programs mentioned above on your home computer. Click "File" in the navigation bar and select "Open" from the drop-down menu. Locate the picture you want to edit, highlight the picture and click "OK." The image will appear on screen.
Click "Layer" in the navigation bar and select "Duplicate layer" from the menu. A layer is similar to a see-through sheet of film placed on top of the original picture. Creating a duplicate layer makes a sheet that looks the same as the picture. You can make adjustments to this sheet and when "Merged" or "Flattened" at the end, the program will change the underlying picture. You can also delete the layers if you don't want to use them in the final picture.
Select "Filter" in the navigation bar and select "Liquify" from the choices. In the tool bar portion of the window, increase the size of the tool to "150 pixels." Using a larger tool will make it easier to change the size of the person.
Place the tool on one side of the individual and move the cursor along the side and towards the middle of the person. Repeat this stroke on the other side of the person, and gradually the person will start to appear thinner in the picture.
Click "Layer" and select "Flatten" or "Merge down" so it can be saved. Click "File" and select "Save as." Give your edited image a new name or title and save the image to your hard drive.