I am sure most of us have made an old style map from time to time only to discover we didn't have a parchment texture to use as a backing for it. When this happens it's generally off to Google to lookup a texture and hope we can get one in a good size to use with our map without violating copyrights. Photoshop has some in-built canvas textures you can use but they tend to have issues with quality and repetition.
Well I finally got tired of having to do this (and tired of photoshop's canvas textures not always working) so I came up with my own way to generate a parchment texture from scratch. Hopefully the rest of you can get some use out of it. It is designed to work with Photoshop CS but I am sure it will work fine in earlier versions (and I know it will work in later ones up to cs4) and someone proficient in GIMP could probably figure out a way to do this in that program as well.
1. Open up a new photoshop document the same size (and resolution if you plan on printing) as your primary map.
2. Fill the map with a light tan color. I use something like #D3CEB5.
3. Go to your noise filters and hit add noise. Add about 5% uniform. Make sure that monochromatic is checked This will help break up our texture a bit for the other filters we will be using.
4. Use an Artistic -> Dry Brush filter. This will mix up the texture and create variations in the texture that will remove any flatness or repetition from the appearance. For settings you can go wild with this. For mine I used these:
Brush Size: 2
Brush Detail: 8
5. Go to filters and apply an ocean ripple (distort -> ocean ripple). This will stretch out the dry brush we used and mix it up even more. Keep your size small and your magnitude around the middle. I used a size of 3 and a magnitude of 8.
6. Add some more noise with noise -> add noise. The same settings as before should work fine. This brings back some of the grain we want for the final texture.
7. Finally we want to make our texture pop out at us like real parchment so go to artistic -> rough pastels. You can tweak the settings on this a bit if you want. The ones I use are my defaults:
Stroke Length: 6
Stroke Detail: 4
8. Hit ok, you should now have a nice looking parchment texture to use for any of your old style maps or canvases.