Just had a look at the stats on this blog and I noticed “straight line” among the search engine terms.


Then I realised that there is no straight line tool in GIMP, which is strange because I use straight lines all the time. Personally I often use multiple short straight lines and a soft brush to approximate curved edges when painting a Layer Mask.


Strangely I have no idea when or how I learned to do this, must have discovered by accident at some stage. It’s is however very simple, in Windows at least, then again everything is once you know .


1. Select the “Paintbrush” or other tool.


2. Left mouse-click where you want your line to start.


3. Press and Hold the “Shift” key on your keyboard.


4. Left mouse-click where you want your line to end.


Viola, you should now have a nice straight line.


I just checked and this “Shift” key trick works with all the tools listed in the image below for GIMP 2.6.2. I was surprised to see that it even works with the “Healing tool”, once you have first defined a clone point.




Solarisation is the effect whereby the properties of a material is affected by electromagnetic radiation.

It’s effects in photography were first discribed in 1859 by H. de la Blanchere and usually refer to the skewed tones which result from exposing an already exposed (used) film to light before or during processing. This effect was popularised in the 1920’s by American painter and phtographer Man Ray.

I saw Photoshop intructions for how to reproduce this effect digitally in a UK photo magazine (can’t remember which one, sorry), so all I had to do was GIMPify these intstructions.

A word of warning, this effect can look good on some images but just doesn’t work at all on others. Image selection is important and you may have to try this effect on a few different images to get one which “works”. The guy in the print shop thought I was crazy when he seen this image first, but he changed his mind once he saw the enlarged print.

1. I started with a photo of a neighbours 1931 Norton. The first thing we do is to desaturate the original image by selecting “Colors” > “Desaturate” from the dropdown menu. I have chosen to do this using the “Average” option.

2. To replicate the skewed tones characteristic of solarisation we need to produce a radical inverted “vee” tone curve, (GIMP shows its class here, as not all applications give sufficient control over the tone curve to replicate this effect). We have two options to create the inverted “vee” curve, a.) we can use the freehand mode, which can give a good, if somewhat wobbly curve. b.) the method I prefer as outlined here. Launch the “Curves” dialog from “Colors” > “Curves” and leave it on the default “Smooth” curve type. Grab the centre of the curve (straight line as yet) and drag it up to the top of the window.

3. Next grab the right hand end of the curve and drag it down to the bottom of the window.


4. Next gab a point on the curve near the top/apex/crest and drag it up and over so it is just beside the topmost point of the curve (I say just beside as two points cannot live at the same place, your top point will have an X coordinate of about 127, so aim to place your new one just beside it at 126 or 128 depending of whether you are dragging from left to right or right to left). Viola one inverted “vee” Solarisation type curve.

You may wish to launch the “Curves” dialog again and do some fine tuning, a gentle “S” curve often works well, I did not feel that it was necessary for this image. Be sure to try this effect out on some portraits, it can really emphasise the eyes and give a very aluminum “Metropolis” type feel as you can see in this photo of my cousins kid.

Happy GIMPin’,


I have been a long time admirer of toned Black & White photographs. I recently read a book on this subject to see it I could use any staining techniques on digital prints (I see some tea and coffee staining experiment sin my near future). This book introduced me to the fact that some toners work from the highlights to the darks and some work from the darks to the highlights, so I thought to myself that this was a principle which I might be able to replicate in GIMP. I call it Quick N’ Dirty, as it is not an accurate representation of real wold toners, but it does produce an interesting image, in my humble opinion.


The original photo is of Cullahill castle in County laois, Ireland. It has had a quick “Auto Levels” adjustment but is otherwise unchanged. Persoanlly I didn’t much care for the colours which seemed oversaturated to my eye.


1. From the “Colors”menu select “Desaturate”. As you can see I have used the “Average” option here, but feel free to experiment.



2. From the “Colors” menu I next select “Curves”. On the “Value” setting I noted that the Histogram suggested slight underexposure, as such I dragged the top of the left slightly.


3. In order to simulate a green toner acting from the darks toward the hightlights I once again opened the “Curves” dialog. This time I selected the “Green Channel”. I mouseclicked in the centre of the curve (Straight line at this point) to add a n anchor point, I then dragged the bottom half of the curve upward to add green to the darker tones.


4. In order to simulate a blue toner acting from the highlight to the darks I again opened the “Curves” dialog and this time I select the “Blue Channel”. I again added an anchor point in the centre, but this time I want to drag the top half of the curve upward to add blue to the highlights (the sky in this case). Note that the curve is not as smooth as the one I used for green, this is because I noticed that the darker area in thetop left corner of the phot was not being affected, so I skewed the curve a little to counteract this.


5. I was going to call it a day at this point, when I asked myself “how would a more purple sky look?”. So back to the “Curves” dialog again, select the “Red Channel”, add a central anchor point and drag the upper portion of the curve upward to add a little red to the highlights. That’s about it, Sharpen and save it off. This effect may not be everyone’s cup of tea but I like the resulting image and it was fun to do.


Happy GIMPin’


The installation of the GIMP on a Windows system is very straight forward. However I do remember an issue which arose a few months ago when a friend of mine decided (was persuaded) to try the GIMP. He was becoming frustrated that every time he double clicked on an image file, the image would open in his old editing application and not in his brand spanking new GIMP installation, exactly the same thing happened with my first GIMP install.


This happens because unlike many other applications the GIMP does not steal file associations when you install it. However there are two simple ways around this.


Method 1: (Custom Install)


1. Double click on the Gimp Install file (get it at www.gimp.org) and the select Run. Select Next at the Welcome screen and Next again at the License Agreement screen.


2. At the Ready to Install screen select Customize




3. I usually leave the Installation Destination at the default and select Next. On the Select Components screen I normally leave it at the default again and select Next.


4. And here is where it gets interesting, on the Select File Associations screen scroll down and select all the file types you want to have associated with the GIMP. At the very least you will probably want to select .JPG and .TIFF but see for yourself as you may have other file types on your computer wish you would like to associate with the GIMP. When your done select Next”.



5. At the Select Start Menu Folder screen select Next and at the Select Additional Tasks screen select Next.


6. This bring you to the Ready to Install screen, select Install here and watch it run. JPG’s and any other file types you selected earlier will now open in the GIMP.




Method 2: (Set File Associations in Windows)


If you have already installed and GIMP you can either run the install again, this time selecting the Custom Install as outlined above or you can set the file associations in Windows, to do this.


1. Open Windows Explorer and from the Tools drop down menu select Folder Options…


2. Go to the File Types tab scroll down the list to. JPG and select Change then select “Gimp-2.6” and select OK. If “Gimp-2.6” is not listed select Browse to locate the file Gimp-2.6.exe manually, it is usually located in C:\Program Files\GIMP-2.0\bin\Gimp-2.6.exe



3. Repeat the last step to add any other file types you wish to associate with GIMP and select “Close” to finish. GIMP will now be the default editing application for the file types you selected.



Just a few GIMP related links which may be of benifit, I’ll probobly add more as I come across them

GIMP Homepage http://www.gimp.org/

GIMP Plugin Registry http://registry.gimp.org/

GIMP User Manual http://www.gimp.org/docs/

GIMP Tutorials http://www.gimp.org/tutorials/

GHUJ GIMP Tutorials http://www.ghuj.com/

GIMP Guru Tutorials http://www.gimpguru.org/Turorials/


Gimpology http://gimpology.com/

Grokking the GIMP http://gimp-savy.com/BOOK/index.html