Attached are some graphics for combined types of electrification: overhead DC plus 3rd rail and overhead AC plus third rail. For obvious reasons, there is no graphic for overhead AC plus overhead DC!
There's a problem with the front/back images as shown in the picture below... The third rail needs to be in the back image and the catenary needs to be in the front image.
How would I separate them...?
May it be I see it more simply than it is but try to do this:
Pillars of upper electrification have to be in back image but wires of that electrification have to be in front images. So pair third-rail electrification with pillars of upper electrification - and move them both to back images.
You may use as hint this (very imperfect) project of upper electrification by myself (pictures are located on graphics.simutrans.com):
Front images:
(http://graphics.simutrans.com/albums/userpics/10043/Elektrifikace160Predni.png)
Back images:
(http://graphics.simutrans.com/albums/userpics/10043/Elektrifikace160Zadni.png)
So add third-rail to back images. And then it would be right. You may use those files as you want ... and need. Their real size is 512*768 and 512*896 pixels.
You probably need to redo them from the two originals (catenary and 3rd rail) - copy the bits from third rail image and put over the back images of the catenary (i.e. the pillar images, not the wire images).
Ahh, I see what you mean! How would I make sure that I aligned/registered them correctly? For the originals, I just aligned them using the toolbar buttons, but I don't think that I can do that here...
Often I put a single black pixel in the top left of the image I am copying, select by colour (not #e7ffff) and paste the result into the correct row of the png image. You'll need to check the black pixel matches up with the correct x,y of the top left of the region you want to paste the image to.
The Hood,
I think that I'm being a little dim, but I don't follow entirely - I put a black pixel in the top left of the smaller of the two images (i.e., the third rail graphics), and then copy and paste that image into the new image - I'm not quite sure that I understand how that helps alignment...?
Think of it this way. Each 128x128 image is aligned perfectly to fit a tile in both the catenary and 3rd rail images. You need to superimpose the third rail images on the back images of the catenary so that each 128x128 tile of the 3rd rail is over the 128x128 tile of the back images (pillars) of the catenary. Here's what I would do in GIMP:
1) open up the third rail image.
2) Place a single black pixel at 0,0 (x,y)
3) select by colour #e7ffff, then invert the selection and copy
4) open the catenary image
5) paste the third rail image
6) align the black pixel from step 2 with 0,256 in the catenary image (i.e. over the back images)
7) anchor the pasted material (ctrl-H)
8) remove black pixel
9) save as combined image
Aha, thank you! How are these?
Yup, that's better. Adding it to SVN now...
Excellent!