The GIMP is the GNU Image Manipulation Program. It is a freely distributed piece of software suitable for such tasks as photo retouching, image composition and image authoring. In the GIS lab, image processing on the Samson server is really impressive.
|Start the GIMP software in a Linux terminal.To Start type gimp & in your terminal, read through the screens that “pop up” and follow the instructions on installing and closing the tips box. You will have to install the gimp if you have never used it before. (This process is Automatic).When all is done you will get this small box appearing on the left side of your screen|
- If you do not have any imagery, probably the first way to get some is to take a screen shot. “Screen shots” are really handy if you want to save some output from your screen and insert into Powerpoint or web based presentation.To take the shot, select FILE -> ACQUIRE -> SCREEN SHOT.A box will appear with only 2 main options. Either take a screen shot of the entire screen or of a single window. You decide what is necessary.If you take a shot of the entire screen you will have to wait for the specified amount of time before a large image appears on your screen. Otherwise if you grab a single window, you will have to click on the Window you want to “grab” to select it.If all went well, you will have the screen shot appear on your screen
- If the image you have is not quite the right size or you just want a portion of it you will have to crop the image.If you right click on the image a list of menus will appear. To crop images choose tools crop.Now draw a box around the portion of the image you wish to preserve, immediately an information box will appear. Click on the “Crop” button to crop.
- In much the same way as a crop, you may wish to reduce or enlarge the size of the image. To do this you will have to use the scale or resize commands.To use these simply right click on the image, and select image resize or scale. 3. You can skew the image in one direction or constrain the dimensions, as necessary. Simply enter the new height and widths, and click okay. 4. Immediately your image will be resized.
- Saving image is probably the last thing you will need to do and often people can run into problems. The Native GIMP file format is an XFC, if you save your image as an XFC your project will be completely preserved but only readily accessible in the GIMP. At some point you will want to save as a different kind of file format.To save your image right click and click FILE -> SAVEAS or SAVE.Choose your file extension and click save.Note GIMP will narrow down your file type options based on what kind of image is on the screen. For example if your image looks like a drawing file extensions such as, .gif .tif, and .bmp are available, alternatively, if your image is like a photograph the JPEG save option becomes available. The key here is file formats are different to suit different type of imagery. It is very important to save your images as the correct type.If you do not know the difference between file formats, take a few minutes and search the Internet to find when and when not to use specific file formats.
- In general the safest formats are PNG (Portable Network Graphics) and TIFF (Tagged Interchange File Format). The reason for this is as follows:
- -these formats are designed to be easily used on any platform with any software.
- -their compression is very simple (and therefore poor) but other formats have better compression and therefore cannot be read by every piece of software. In this day and age, file size is becoming less of an issue and file interchangability is more important.
- Saving a .GIF file requires an extra step.
- The extra step is to index the image.
The reason for indexing is as follows. A GIF can display layers in sequence as seen in animated GIF like the following. Considering this you must tell thisorder before you are saving.
- To index an image right click on the image and click IMAGE -> INDEXED
When you go and resave the image, GIF should be an available file format.