Vroid Studio has just come out of beta and is now at release 1.  I use it to create anime-style hair geometries for use in Poser and Daz Studio.  The terms of use for content created with Vroid Studio are very generous.

One less well-documented feature is how to extract the corresponding hair textures.  I created a visual guide to show how to extract the hair textures using Vroid Studio.  

I tried uploading my visual guide images here, but for some reason I got an error from the web server.  Anyone who is interested my take a look at the items at my personal website here 

I will try again to add the images in this thread.

1. In the Hairstyle section, left click Edit Hairstyle.  (This is an original hairstyle I created.)

2.  Left Click on your hair group.

3. Left Click on a Material.  (I have more than one Material group in my hair mesh).

4.  Left Click Edit Texture as shown.

5. Right Click on each texture item as shown in my example.  Your hair may have a different coloured item from mine, if you have customised it).

6. From the pop-up menu, Left Click on Export.  Done.