CMPT 165: Using The GIMP

Saving Files

The method to save a file as a PNG/JPEG/GIF image isn't as obvious as it should be in newer version of GIMP. To save a file (as something other than GIMP's own XCF format), select “File” → “Export…”.

Then name the file with an appropriate extension: something.png, something.jpg, or something.gif.

The Toolbox

In the bottom of the image above, you can see the current colours which are displayed as two overlapping rectangles. The top colour is the foreground colour; this is the colour that will be used for anything you draw. Behind it is the background colour that is used when you erase something. If you click on either of these, you will get a colour selection window where you can change to a new colour.

Above the current colours are several tool buttons. We will discuss some of them here; you can play with the others on your own.

If you double-click any of the tools, you will activate the tool options window. Different tools have different options; feel free to explore them as well.

First, the pencil tool is used to draw. You can change the size of the line it draws by double-clicking it and using its options screen. You will see many different brush shapes and sizes that you can choose from. The eraser works exactly like the pencil, but it uses the background colour, so it erases instead of drawing.

The buttons in the first row are used to select parts of the image. When part of the image is selected, that's the only part that you can change. The select rectangles button and select ellipses button are used to select simple shapes.

Once you have made a selection, you can use the move tool to move it around. You can also use any of the other tools, but you will only be able to change the selected region. Creating and working with selections can also be done by using the “Select” and “Edit” menus.

The Zoom tool is used to magnify or shrink your image on the screen to make it easier to work with. Clicking on part of the image magnifies the image more, keeping that part in the display. Holding down the control key while clicking zooms out. The Crop tool is used to shrink the image, keeping only part of it.

The rest of the tools you can explore on your own. If you move the mouse button over a tool and leave it there for a few seconds, a short description of the tool will be displayed.

Menu Items

As in the case of the toolbox, there are far too many options in the menus to cover them all here. We will explain the fundamental ones, and then you're on your own to explore the rest.

You can change the colour depth of the image by selecting “Image” → “Mode”. Colour depth is described in Unit 5 of the Guide. You have three options here. “RGB” refers to 24-bit colour; “Grayscale” refers to 8-bit colour consisting of 256 shades of gray; “Indexed” selects an 8-or-less bit palette.

The ``Layer'' menu has many options. Basically, your image can be made of many layers that can be manipulated separately. Feel free to explore layers.

If you are working with an image and you find that some of the image just won't change the way you think it should, it might be on another layer (occasionally, GIMP creates layers at unexpected times). To get rid of the layers, select “Image” → “Flatten Image”. All of the layers in the image will merge.

Something else that's easy to overlook is the current selection. Remember that you can only change the pixels that are currently selected. To get rid of your current selection, select “Select” → “None”.