Graphics Made With GIMP

The most important questions to ask as you work to understand the graphics of the free image manipulation program GIMP relate to image transparency, layers, animation, and vectors. Knowing how GIMP handles these characteristics of digital images will give you a good overview of what tasks you can perform with this program. For example, knowing that GIMP uses layers, which are virtual transparencies, enables you to add new images to existing pictures without destroying the original picture's information.

Raster Versus Vector

GIMP graphics are of the raster type, which means that GIMP stores image data as a sequence of bytes, which are units of digital information. Raster images are one of two popular formats for image data. The other is the vector format, which stores images as instructions that indicate to a graphics program how it should recreate an image. Since raster images store an image's visual parts, you'll degrade the image quality if you enlarge those parts enough to make them visible. Vector images, which have no such parts, will maintain image quality no matter what size you scale them to.

Opacity

GIMP graphics are variable in transparency. This means you can adjust how much of the graphics from underlying layers are visible for a particular layer. For example, if you have two layers in a GIMP document and set the top layer's transparency to half by dragging its "Opacity" slider to "50," any graphics on the bottom layer will be partially visible. This variable transparency is lost if you export a GIMP image to a format that can't handle transparency, such as JPEG or PNG. To preserve the variable transparency of the individual layers in your GIMP images, keep images in the GIMP format, or in the PSD format, which Photoshop can open.

Portability

You can export GIMP graphics to other image formats, though doing so will often result in a loss of information from your Gimp source file. GIMP's export formats include the two image types most commonly seen on the Web, JPEG and GIF, including animated GIFs. GIMP can also export its images to a file type that is not an image format at all, but a text file holding statements from the popular programming language "C." Exporting to this extension makes GIMP create a C program that recreates your GIMP image. You'll need a C compiler to make use of this format.

Animation

Some GIMP graphics are animated. GIMP will convert an image's layers into animation frames, if you try to save the image in the GIF format. Once you choose this option, GIMP will display a message asking if you'd like to create animation frames from your image's layers. While saving to this format, GIMP lets you choose the time lapse in between the animation's frames. Note that you may lose color information if you save in the GIF format, which can only store 256 colors.

References

• "The GIMP User Manual"; GIMP Documentation Team; 2009
• GIMP: Simple Animations

Resources

• GIMP: GIMP Manual