Ability to handle multiple image sets simultaneously

[johnbeech]

Raised by email request:

If you look at the attached screenshot, you'll see how some of the files I was piecing together were named. In this example, I had a total of 25 "whole" images that were broken into 9 parts each, named "heroes_01_01.png" to "heroes_01_09.png" through "heroes_25_01.png" to "heroes_25_09.png". I was hoping that Tile Merger could see this entire folder and, after setting it to "top-to-bottom" and "3 rows", would be smart enough to merge this entire folder into 25 images named "heroes_01.png" through "heroes_25.png". So, that's where this suggestion comes from.

So specifically in this example; recognise a base pattern "image_prefix_01" and a number suffix "01.png", "02.png", ... "25.png" etc. and merge them all as part of one operation.

Not sure what to name this feature, but seems like a cool workflow to support.

[johnbeech]

See: #11 feature could be called Identify Common Prefix.