Image shows a problem to beware of in Gimp: a dialogue box is hidden behind the toolbox.
This lecture introduces image editing software. It assumes you already have an image – either a digital photo or a digital drawing. You may wish to do the digital drawing techniques lecture first. It would be best to be playing with a pre-existing image while you work through this lecture.
I will be introducing various principles for editing digital images. Good image editing software will allow you to do these (and much more). I will refer to Photoshop, the industry standard, and GIMP, which is a free download. There are many resources available and I’m not going to reinvent what already exists. This lecture will present basic image editing principles in an appropriate order. The software does much much more than this – if you’re into it, you’ll explore further on your own. There are often quick keys associated with these processes, which will speed up your workflow.
1. Open and Save/Export
You need to open your image in the software and save/export it. You may be able to drag the file icon onto the software icon to open it. Otherwise, go file (top left hand menu) – open – then navigate to your image. If you want to create a file, go file – new – then determine the dimensions etc in the resulting dialogue box.
Note: In GIMP, there is often an extra dialogue box that you have to go through when you are doing something. This often hides behind the toolbox (yes, its a design flaw, but GIMP is amazing and free! I’m not complaining!). If nothing is happening, hunt around for this dialogue box.
Saving is more complex. There are many different image file types, some appropriate for web (jpeg, png and gif) and others appropriate for higher quality print (TIFF, eps). You can also save as a pdf – the digital publishing standard run by Adobe. This is for stand-alone digital files (ie, not viewed via a browser or other software). Make sure you are choosing the right file type for its final destination. For Web and other digital contexts, you would usually save a photograph as a JPEG, because it compresses the image while maintaining the image quality quite well. A gif file will have a certain (somewhat outre) appearance without as much detail. Possible for cartoons etc, but even then, a jpeg is more likely unless you want that retro look. A PNG file may be a good alternative to a jpeg.
In GIMP, go file – export – then select file type at the bottom of the screen.
In Photoshop, go file – save as – then select file type. There is also a ‘save for web’ option which is great if you want to fiddle with the options and get immediate feedback on the effects.
Tip: make sure your image is the correct dimension (ie pixel/millimetre size) for its final destination before saving/exporting (see resizing).
2. Resize and crop
Resizing refers to changing the pixel or mm dimensions of the image. Cropping means removing one or more sides of the existing image to re-position some part of the image that you like. These are very different activities, and sometimes you may need to do both. However, make sure you keep your original intact. Always work on a copy, not the original.
In GIMP, go image (top menu) – scale.
In Photoshop, go image (top menu) – image size – then make you adjustments.
Note: Resizing an existing image may not work too well if the original is of low resolution.
In GIMP, find the toolbox tool (it looks like a scalpel) and select the area, then return.
In Photoshop, find the angular tool in the toolbar (fifth from the top). Draw a square representing the area you want to keep. Hit ‘return’.
Any action which edits the actual image requires you to work with layers. If you don’t work with layers and do something you later want to undo, you may not be able to undo. Each layer should contain one aspect of an image – for example, one text, one photograph, or one drawing. Make copies of important layers, then hide them, in case you need them later. Experiments should be carried out in layers, so you can trash the layer if you don’t like the experiment, but you don’t lose the rest of your work.
To show layers:
Both Photoshop and GIMP have a new window for layers. If they are not obvious, In GIMP go to the top menu ‘Window’ – ‘dockable dialogues’ – layers’. In Photoshop, go to the top menu ‘Window’ – ‘layers’.
Once you have the layers window showing, you need to learn how to create and trash (bottom of layer window for GIMP and Photoshop, the bin icon) layers. Note there are different sorts of layers for different types of actions.
To create a layer
In GIMP, Layers window top arrow – layers menu – new layer. This generates new (sometimes hidden) dialogue box that you need to agree to. Usually you’ll want a transparent layer.
In Photoshop, Layers window top arrow – new layer.
4. Altering the colour range in an image
You may need to do this to make the image blend better with a pre-existing colour scheme, or you want to digitally improve the brightness, etc. There are a variety of tools, and no matter how you good you get at it, experimentation is always necessary.
Altering the colour range:
In GIMP, go to the top ‘Colors’ menu, then you need to play with the first 7 of the options.
In Photoshop, go Image (top menu) – Adjustments – then you need to play with the first 8 functions in that drop down menu.
Tip: You’ll find that many of them won’t have any impact on a black and white image (or they’ll be unavailable).
5. Adding effects
Referred to as filters in both Photoshop and GIMP. They can be over-used, and if you have a series of images, it is important to write down what effects, and what order, you are using them in, so you can re-create them. (Advanced users can set up rules). A commonly used and very valuable effect is blur.
To add an effect:
In GIMP and Photoshop, go to the ‘Filters’ top menu then (for example) blur – Gaussian Blur.
Gimp and Photoshop offer a variety of tools in the toolbox window (some of them have already been mentioned). these are bit of programming which require you to use your mouse/trackpad. I mention only the most commonly used ones.
You may need to draw on an existing image (eg, to touch up a bit that you don’t like). Remember to do anything like this on a different layer so you can get rid of it. To draw, you will need to know how to select a colour. You will probably also need to zoom (in Gimp, toolbox magnifying glass; in Photoshop, lower left corner – change the percentage) in on the image (possibly until you can see individual pixels).
In GIMP, pencil and paintbrush in the toolbox. Alter the color in the box colour box under the tools.
In Photoshop, pencil and paintbrush in the toolbox.
In GIMP, the pink eraser tool in the toolbox.
In Photoshop, the rectangular eraser tool in the toolbox.
selecting an area
Important if you want to do something to a specific part of an image but not all of it. Make sure you are working on the correct layer. In the toolbox, you have a choice of a rectangle, a lassoo, or an elipse.
In GIMP, toolbox – first three tools.
In Photoshop, toolbox – first two tools (clicking and holding the tool gives you more options).
In GIMP, the ‘A’ tool in the toolbox.
In Photoshop, the ‘T’ tool in the toolbox.
In Photoshop, the line tool in the toolbox (near the T)
Look on Youtube for tutorials. There are also lots of books. Make sure whatever you use, it is referring to the correct version of the software.
Further resources for Photoshop
I tend to rely on the Photoshop help menu.
Further resources for GIMP
There are lots of online video tutorials for learning Gimp.
There are many video tutorials for Photoshop on Lynda.com (and a couple for Gimp). To access Lynda.com as an RMIT student for free, go to the RMIT library website and chose the databases tab. Choose Lynda.com in the database titles menu, then ‘go’. You need to create a different Lynda password.
I heart Gimp!
[Written for Contemporary Media Work Practices, a course at RMIT University]