i need a way replace a section of a link with something else instead. for
example, when HTTrack finds a link like website.com/image_001_512.jpg it
downloads this link instead website.com/image_001_1024.jpg

is this possible or is there another way of doing it?
this is the problem. a folder has many images in it, but the folder is set to
forbidden access unless you call the file specifically, so you can call each
image from the browser but you can't download the folder without using a link
that includes that images name and format.

using HTrack i can get the thumbnail images of each image. behind each
thumbnail is a link to a html page with the image embedded in a javascript
viewer, so HTTrack doesn't download the image because it isn't actually a
link, it's just a url path to the image. and that is actually what i need to
grab. but it turns out the the thumbnails are named exactly as the full size
images except for the trailing 512.jpg vs 1024.jpg so if i can get HTTrack to
download 1024.jpg when it sees 512.jpg, i would have a working method.

it is a huge archive, i could do this by hand if it were even several hundred
links, but this is going to involve tens of thousands of links so the swap of
512.jpg for 1024.jpg has to happen on the fly.

i hope i've haven't been too confusing and i hope i can get some advice on how
to accomplish this. 

thanks.