Use path stroking, noise and layer manipulation with GIMP to make this Wilber Constellation for your GIMP splash image.
This tutorial assumes an understanding of GIMP layer manipulation techniques including masking and modes. Python and Perl plug-ins have been used, but they are unnecessary conveniences and are not actually needed to make this image.
The first task is to import the Wilber.svg. Instructions for this can be found in the import svg tutorial.
Once the imported svg is there, it needs to be transformed and moved around to fit the image. The paths plug-in will be helpful for this if you have gimp-python installed. Once it is installed, you can select <Image>--> Paths--> Set Paths Visible to see where the import put the paths. If you are using an older gimp, setting just the head and shadow path visible should give the same information.
The paths have been imported to the upper left portion of the image area. Using the paths plugin again and using the menu option Link All Paths, you can easily prepare the paths to be moved and transformed.
Linked paths will move together with the move tool. Through the Tool Options you can tell the move tool to move paths. With the Move Tool selected <Toolbox>--> Tool Options--> Affect; the choices are Layer, Selection or Paths.
If the paths are all linked, it the Tool Toggle should make no difference in (any path or current path) the move transformation.
When making my image, I simply used the move tool to centre the layer. Using the other transformation tools (like Scale whose options are shown here) I could have changed the size of all the paths or rotated them, and more.
To help me with moving the paths, I used <Image>--> Image--> Guides--> Center Guide with the options set to "Optical" This plug-in is installed with the gimp-perl module.
These paths that draw Wilber will be used as a mask later. I do not want all of the lines to be stroked with the same width of stroke. The paths plugin is able to stroke all visible paths. Since I will be using three different widths of stroke, it will be safe to stroke all paths with the most narrow stroke.
I decided against having the highlight areas in my Wilber constellation so the nose and pupil highlights have been manually set to be invisible. The shadow and head paths are also manually set to invisible so that we only stroke the paths that are needed.
First, all paths were stroked with the Custom Brush set at 3.0 pixels wide 90% hardness. I made sure that my custom brush was the brush the toolbox knew about and used <Image>/Paths/Stroke Visible Paths.
After that first stroke, toggle to invisible paths you want to have this narrow stroke. For me it was just the eye pupils. Make the brush a few pixels bigger for the next stroke, 5.0 pixels.
Toggle the nose and eyeball paths to invisible and stroke the remaining visible paths with the brush set to 7 pixels.
Without the script, the paths will need to be stroked individually.
Remove the guides with <Image>/Image/Guides/Remove Guides and <Image>/Paths/Set Paths Invisible then <Image>/Colors/Invert to finish this layer which will be the mask (and a little clean up where the paths did not end at the best place).
This white on black image will be used as both a Mask and as an Overlay Moded Layer in the final layer stack. Now it is time to make some noise....
When I was first fumbling around with GIMP, I had the pleasure to hear from artists like Artwiz and Tigert how they made images. They both used noise. Noise is one of the more interesting pixel manipulation thingies -- vector art will never have the richness in imagery does when made with noise on pixels. That being said, I still don't understand noise all that well. GIMP has a bunch of plug-ins and each of those has a large number of combinations of settings. I usually have to play with them a little each time I use them again.
The goal is to have two different layers of noise. One with bigger chunks (to be the constellation) and the other to be the background non-constellation stars. In all honesty, a more photo-realistic Wilber constellation was already made by Seth Burgess with one star in key points of a bunch of stars. This is more like a Wilber galaxy with clusters along paths and totally impossible. It looks good though...
The way to get mono-coloured noise like we need here is to use <Image>/Filters/Noise/RGB Noise make sure that both Correlated noise and Independent RGB are toggled off. I probably ran it at .37 or .42 because I pick numbers like that when I am just guessing and it involves a computer and not a human.
Duplicate the layer and run the same filter again, with the same settings. You will get a noisier image. Then I ran <Image>/Filters/Noise/Slur three times in a row with the default settings. After that, some adjustment with the Levels Tool and there is a layer with big stars on it.
Nonindependent RGB Noise 0.37, Slur, Levels Adjustment |
Nonindependent RGB Noise 0.42, Slurred three times, Levels Adjustment |
Stroked Wilber path will act as a mask and as a moded layer. |
Scaling the layers down to fit on the web page hid the noise that are on the layers. You can click on the thumbnails to see the full sized noise that has been rendered there.
First I copied the layer of stroked Wilber paths and pasted it to the mask on the big star layer. Then I duplicated the Wilber layer and moved that to the uppermost position in the stack and changed the layer mode to Overlay.
This is the first splash image in my gimp-2.4 gallery. The full-sized xcf and the smaller splash sized xcf for this tutorial have been made available.
