Sponge (reticulation, pores) texture in Inkscape
I'm trying to vectorize this Gray's anatomy diagram from the Wikimedia commons:
(Yeah, I know. Kind of an awkward image, but I'm a medical student studying Urology and we need good medical diagrams too.)
I'm trying to find a way to replicate the spongy texture in the image in the least painful way possible. I've looked into using texture images and masking, but the textures I've found are either the wrong color or just too jarringly different from the cartoon-y diagrammatic style of the rest of the image.
I'm trying to avoid having to hand-draw tons of little shadows/pores here, but if that's what it takes, any suggestions on how to do that efficiently would also be appreciated.
I know you tagged your question with inkscape, but this is how I would do it with Illustrator. Maybe you can do the same in Inkscape, but I'm not all that familiar with it.
1. Start with an arbitrarily colored rectangle
2. Apply a Stained Glass Texture to your rectangle
Effect > Texture > Stained Glass...
Adjust the settings as you see fit!
3. Vectorize with Live Trace
I used the "Color 6" default, we'll remove the color in the next step.
(You must first expand the appearance to be able to live trace the stained glass texture)
I selected the black webby-shape and moved it to another layer so I could ignore all the red. Then I created another rectangle (same size as the artboard) and used Merge to "invert" the shapes, then deleted the black webby-shape.
4. Apply a Clipping Mask
This is also apparently a good way to generate a giraffe skin pattern :)
JohnB's answer is definitely the best technique for Illustrator. Just in case, I thought of an alternative idea that you can use in any program.
I found this cracked soil texture in CG Textures (category Soil, there a few similar ones):
And adding a black and white filter and a Photoshop effect called Stamp, I ended up with this:
Because it's a seamless pattern, you can repeat it and use it as a background.