Screenshot the map preview in the game lobby
Open this image with Paint.net, remove green background (make it transparent). You can either work with it at double resolution, then downsize it at the end, or downsize it now by 50% (Highest quality setting). We'll call this guy "Small"

Make a new image with many layers:
Layer1: Axes, place grey lines bisecting both sides. At this point you may notice the map-maker hasn't made a symmetric map. Generally, you want ones with dimensions multiples of 2, to be able to place buildings exactly in the center
Layer2: Default map layout. Layer settings to xor, opacity 150
Layers3-5: Copies of "small" flipped along all axes (Flipping applies to the whole image, not just a single layer, socopy the image to a new instance, flip there, and copy back. Layer settings to Multiply, opacity 60

You should now have an image that super-imposes all spawns. Places where they overlap are shown as darker. The original layout is shown in inverted color, so dark red cliffs show as cyan, and cyan tiberium shows as dark red. This way you can track how the average compares to the original.

Now add another layer to your image "best-fit", and trace by hand what you think is be best fit FOR ONLY ONE QUADRANT. Use grey for start locations, black for cliffs and bright green for tiberium spitters (and dark blue for blue spitters). Make sure the cliffs are minimum 3-sideways and 2-diagonal units away from the spitters. Also, trees and some doodads won't show up in the preview image, so won't be here. Treat them like cliffs and include them now, because you don't want to have to come back to this step to add them back in later.

Since we're making an axially-symmetric map, the one quadrant will work for all other quadrants.
Make a new image, and again make the Layer1 be background axes
Layer2: "best-fit" in all its glory. Layer settings default
Layers3-5: Copies of "best-fit" flipped along all axes. Layer settings default.

Now you should have your perfectly symmetric image! Duplicate this, and merge it down to "v1"
Now, "v1" may still not be perfect, if the dimensions aren't quite right (e.g. Manufacturing Consent by Psydev is 96x83, when it should be 96x84 to be able to have the 2x2 building in its center) make a new image of the right size, copy "v1" in, select and adjust manually = "v2"

Now it is perfect!

If you want you can make some nice before-after comparasions (or even a .gif if you're ambitous)
Image1: A color-inverted version of "small". Re-color cliffs to dark red, and the tiberium to cyan (you'll have to change the colors on a separate copy of "small", then downsize it)
Image2: "best-fit"
Image3: "v1" (or v2, but being a different resolution, it might not be an apt comparion).


But how on earth do we convert beautiful "v2" into an actual map? Should we try to count out pixels in the map editor, and place everything by hand? BY NO MEANS! We saved effort by duplicating the quadrant via symmetry. There's a way to get all the information into the map editor without having to count anything else: convert the image to a text file, and change the coordinates of the pixles (dependent on colour) into different actors in the uncompressed "map.ymal", then paint over the location of those actors! (A good way I find is to pick a particular cliff piece, and go around applying that shape to wherever it'll work. CnC is wierd when it comes to cliff geometries. Maybe i'll look wrong, but that's fine. Being FAIR is much more important than being PRETTY!)


Install Cygwin, making sure you include the imagemagick package

	convert map_image.png map_image.txt

Sort by color (use Sublime Text like a boss to split each line after the coordinate, move it 1 up, then merge with the suceeding line)
Do the grey, green, and blue declarations first, and black ones last

	nl map_image.txt > map_image1.txt

This will append line-numbers to each line, which you need to use to differentiate "Actor0", "Actor1", "Actor2" etc.

Grey:
	Actor0: mpspawn
		Owner: Neutral
		Location: 15,23

Green:
	Actor4: split2
		Owner: Neutral
		Location: 3,33

Blue:
	Actor26: splitblue
		Owner: Neutral
		Location: 3,33

Black:
	Actor27: v13
		Owner: Neutral
		Location: 26,3


With like 700+ different actors, there's no way you'll type all this in manually. I guess you could write a bash script to insert the right stuff, but I can't be bothered, just use your text editor.


CRUCIAL: Your indentation needs to be exact (1 tab for Actor, 2 for Actor's parameters). Plus, what Paint.net calls (0,0) is called (1,1) in OpenRA. Coordinates from "map_image1.txt" need to be incrementd by 1 to work in OpenRA. Now if you use Sublime, incrementing numbers is super-easy - just install the 'Super Calculator' plugin, select for all coordinates (e.g. select-all "Location:" lines to select the lines with the right numbers), put a "+1" after the numbers, then calculate.


Voila! You should now have a map that has spawns, spitters, and a shit-ton of yellow everywhere <: . Now just paint cliffs over the yellow! Remember, fairness is more important than prettyness. Use trees to cover up discontinuities and blemishes. Don't forget to layer rocks under sparse trees just to make sure they're impassable. It's plesant to narrow chokes with villages/rocks/trees.


I don't know how this works, cuz I'm just a script-kiddy really, but what I love about this open-source project is that it's all out there, just in text files, so I can simply copy-paste the relevant code and it'll work!

I took this from Manufacturing Consent's "Players:" category:

Players:
	PlayerReference@Neutral:
		Name: Neutral
		OwnsWorld: True
		NonCombatant: True
		Faction: gdi
	PlayerReference@Multi0:
		Name: Multi0
		Playable: True
		Faction: Random
		Enemies: Creeps
	PlayerReference@Multi1:
		Name: Multi1
		Playable: True
		Faction: Random
		Enemies: Creeps
	PlayerReference@Multi2:
		Name: Multi2
		Playable: True
		Faction: Random
		Enemies: Creeps
	PlayerReference@Multi3:
		Name: Multi3
		Playable: True
		Faction: Random
		Enemies: Creeps
	PlayerReference@Creeps:
		Name: Creeps
		NonCombatant: True
		Faction: gdi
		Enemies: Multi0, Multi1, Multi2, Multi3



And your map should now be done! Well, not really. Now's time for decoration and doodads. Please be consistent with your (e.g. tree) placement! If its un-walkable, it's the same as a cliff, so its no fair to have a bunch of trees around the main-base chokes of half the bases (i.e. the bottom bases in Manufcturing Consent) without them also being there in the top!
Hopefully you rememberd to think about trees and doodads BEFORE now, so they're included in the symmetric image. If not, I guess it's not the end of the world, but we've gone through such trouble to be symmetric, it'd be a pity to fail now.