Update: Varying the Color of Trees and Forests
Hello ProfGremli! OK, so, with regard to blending the color of the individual trees with that of the main forests you have at least two options. First, you can alter the color of the trees pattern. Second, you can alter the color of the main forests. Since you asked about how to alter the color of the trees pattern, I'll address that question first. However, before I do, I would also like to mention that since writing this tutorial I have learned that it is a good idea to use a range of colors (e.g. dark Brown, dark green, light green, yellow) within your forests to make them more diverse and lifelike (see the attached image for an example). This means that you will both want to use a range of different colored tree patterns, and create a new "Tree Color" (or alternatively, use an existing tree color layer) in which you paint multiple colors on the same layer (see the second attached image for an example). I'll touch on this more in a minute, but first let's address your question.
- Altering the Color of Tree Patterns: For the benefit of anyone else reading this, what we are discussing here is how to alter the color of the Tree Patterns which I uploaded in a zip file in an earlier post. Now, assuming that you have copied these files to the patterns folder of GIMP (see earlier posts for details), when you open GIMP the tree patterns should show up within your Patterns Tab (if I'm not mistaken I think I included 3 different colored tree patterns). Right Click on any one of these Tree Patterns and select "Open Pattern As Image". This will open the pattern file for that Tree Pattern. Next, zoom in to about 200% so that you can see the tree patterns in better detail. With the "Select By Color Tool" (Threshold set to 15) select any transparent point of the image (e.g. don't select any of the trees) and invert the selection (Select > Invert). Now all of the individual trees ought to be selected. Next create a new Transparent layer called "New Color". Choose a color from your Foreground/Background Colors that you want to replace the existing color with. Next, with the Bucket Fill Tool, fill the selection of the "New Color Layer" with the new color. Next change the Layer Mode of the "New Color" layer to Hard Light. Duplicate this layer. You should end up with trees that closely approximate the new color you have chosen, though you may need to add additional layers and or experiment with the Layer Modes to get the color just where you want it. Next right click on any of the layer and select "Merge Visible Layers". Finally, rename and save the pattern file. Now, close GIMP, and restart it again, and you should find the new Trees Pattern image has been added to your GIMP patterns.
- Varying the Color of Your Forests: In the original Tutorial I suggested making three different "Tree Color" layers (Brown, Green and Yellow) all whose Layer Modes were set to "Soft Light". Well, as previously mentioned, I've experimented with forests a bit since writing this Tut and have found that (a) its better to have a variety of layers of different colors each of which is set to different Layer Modes (and at least one of which is a green layer whose Layer Mode is set to "Multiply"), and (b) it's also good to diversify the colors of the forest by adding a variety of different colored tree patterns and by adding a Tree Colors Layer that itself contained a combination of different colors. At this point I've done allot of experimenting but haven't yet developed anything like a standard method for creating forests of varied colors; each time I experiment with a new map I change some things around. Still, to give you an idea of what's involved, below you'll find an example of a forest I created for one of my most recent maps. To achieve the diverse colors within this forest I used at least 3 different Tree Patterns ranging in color from Brown, to Dark Green, to Yellow. I also used 7 different Tree Color Layers. The first Layer was Dark Green (1d2300) and was set to Overlay. The second and third layer were both Green (3b580e), but the Layer Mode of the second was set to "Overlay" while that of the third was set to "Multiply". The fourth layer was a yellow green color (869f30) set to "Soft Light". The fifth layer was a light olive green color (b5b57e) also set to "Soft Light". Finally, I added a multicolored layer. I began by duplicating the yellow-green layer and then painting a dark Rust-Orange over certain parts of the forest, and a light yellow over other parts. Then I added a slight Gaussian Blur to this layer (10px) and set the Layer Mode to "Soft Light". I then duplicated this layer and added a second Gaussian blur (20px) and kept the Layer Mode on "Soft Light" (see the second image below). At any rate, that's how I created "this" forest, but I encourage you to experiment with colors and layer modes to come up with a multicolored forest that suits your own tastes.
arsheesh's Turorial available in the "Tutorials in PDF Format" thread
Just wanted to let you know I've linked arsheesh's great tutorial. It is available in the GIMP-Related Tutorials section in Post #2 of the Tutorials in PDF Format thread in the Tutorials/How To forum.