GIMP, which stands for GNU Image Manipulation Program, is powerful graphics software that can be downloaded for free. Not only can you edit photographs and build raster images from scratch, you can add filters and common effects like drop shadows and outer glow. Making clothes transparent in GIMP can be as simple as a few clicks of the mouse. All you have to do is add an alpha channel for transparency and then remove the clothes with any of several selection tools.
Prepare the Image in GIMP
Open the image in GIMP. GIMP can open all of the common image filetypes: .jpg's, .gif's, .png's, .tiff's, .bmp's, .ico's, .psp's and even .pdf's. Navigate to the folder where your image is stored and open the file.
Find the "Layers" panel. When your image is open in GIMP, you'll see a narrow "Layers, Channels, Paths, Undo" window on the right side of your desktop. Halfway down, you should find the "Layers" panel.
Right-click on the only visible layer and choose "Add Alpha Channel." This adds transparency to any image you're working on in GIMP. Any part of the image that you delete from now on will show up transparent in your finished product.
Save the image as a .png, .gif or .tiff. These are file types that preserve transparency. If you save as a .jpg or .bmp, you'll lose any transparency you've added.
Delete the Clothing
Select the areas you'd like to make transparent. There are several tools provided by GIMP for this purpose. The easiest method, if the clothing is monochromatic (one color), is to use the "Color Select" tool on the top right of the toolbox panel.
Use the "Paths" tool (which looks like an old-fashioned fountain pen) to carefully trace the area you'd like to delete. When you've closed the path, you have a few options. You can "stroke the path," or add a black line to the edge, by right-clicking on the path and choosing "Stroke Path." Then go to the "Layers, Channels, Paths, Undo" panel, and in the "Layers" palette, choose the third "Paths" tab. There you'll see the path you've just created.
Right-click on the path and choose "Path to Selection." Then hit "Delete," and the clothing will become transparent.
Ultimately, the trick is adding the alpha channel and saving the file as an image type that preserves transparency. There are lots of ways to delete the clothing once those two steps are completed. You can try the magic wand or use the "Scissors Select" tool for intelligent edge-fitting. You can even use the manual eraser to do it.
Remember to save your work frequently in order to avoid losing it.