Creating image transparency in The Gimp is very handy, specially when you are a web designer. Image transparency is specially useful in websites where you have backgrounds with patterns; it makes blending these images a lot easier. If transparency is available the image will have to be created using part of the website’s background as its own and would have to be then positioned with accuracy so that it blends following the website’s background pattern. This, as some of you may know, is very hard to achieve. In this tutorial I will teach you how to make transparent images in formats such as gif, png and bmp, using what is undoubtedly the best free and open source image editor: The Gimp.
Add Alpha Channel
Open your image. As you can see, the image has a uniform color (white) as background; this is ideal to create a transparent image. You will later see why.
On The Gimp’s main window, click on “Layer“, then on “Transparency” and finally on “Add Alpha Channel“, this will add transparency to the picture.
Now, the white areas in the picture have to be cleared so they can become transparent. If the color you are deleting does not gradually mix with the object on your picture, you can use the magic wand, however, if the picture had a shadow that gradually blends with the background, the magic wand is not a good option.
Deleting Color Areas With The Magic Wand
To delete these areas, select the Magic Wand tool from the toolbox.
Click anywhere on the white space surrounding the glasses in the picture. The magic wand will select all the contiguous white space.
To delete this white space, just click on the “Delete” key on your keyboard, or click on “Edit” and “Clear“, on The Gimp’s main Window. The following picture shows the final outcome. As you can see, all contiguous area surrounding the object was cleared and became transparent. To delete the remaining white spaces in the glasses, repeat the same operation with the magic wand.
Ideally your image must have a uniform color; if it does not the process becomes longer and more cumbersome, since the “magic wand” or “select by color” tools become worthless and everything that needs to be deleted must be done manually.
Deleting Color Areas With The Color Select Tool
The Color Select Tool as its name indicates, selects all areas in the picture, contiguous or not, that have the same color. This is ideal when the object on your picture has a shadow, since it will leave the shadow and delete only the color that blends with it; the color you selected to be deleted. The disadvantage with this tool is that if you have parts of your object that have the same color you are deleting, it will delete them too!
To clear areas using the “Color Select Tool” go to the toolbox and select it.
To clear the area containing the color you wish to delete, you are basically going to repeat the same steps as in the previous section. Click on the area containing the color that you wish to clear, then click the “Delete” key on your keyboard or click on “Edit” and “Clear“.
As you can see the “Color Select Tool” selected every single part on the image, not just the contiguous areas.