This tutorial is a list of the steps you need to take to edit a GRF file, and if you like, send your modifications to others.
Since all GRFCodec programs are command line utilities (no graphical interface is built in), you have to make yourself familiar with the DOS or Windows command prompt. However, that's beyond the scope of this tutorial.
On the other hand, you could just use the GRF Wizard, which automates the steps to decode, encode and diff the graphics files. You can get GRF Wizard from the GRFCodec homepage.
These are the basic steps to modifiy a GRF file:
grfcodec -d trg1.grfThis will decode trg1.grf, and put an editable PCX file in the SPRITES folder. If you have the Windows version of TTD, substitute trg1r.grf instead of trg1.grf.
Note that the image will be quite huge (800 x 19000 pixel), and if you instead want to split it into smaller files, use
grfcodec -d trg1.grf -w 800 -h 600
After the -p option, you specify a number indicating which palette you want. You have the following choice:
|3||DOS TTD, Candyland|
|4||Windows TTD, Candyland|
|6||TT Original, Mars landscape|
So, for example, use "
-p 2" when you're decoding a file from the Windows
version of TTD, like so:
grfcodec -d trg1r.grf -p 2
You should then load trg1.pcx in the SPRITES folder. Or, if you used the second command above to split it into smaller files, open trg100.pcx, which is the first part. The following parts simply have higher numbers.
If at this point you find that the colours are wrong, you need to decode the GRF again, using a different colour palette. In that case please follow the instructions in step 1a).
If however everything looks fine, you can then start changing the sprites. Note that it is fairly difficult to actually change their size, but changing the look is easy enough. (Read the GRFCodec documentation to find out how to change the size.)
Once you've changed all you need, save the PCX file again.
grfcodec -e trg1.grfThis will take a bit longer than decoding, but shouldn't take too long. Once it's done, you can start TTD and see the fruits of your labour!
If only there was a way to send only the changed sprites...
...and luckily, there is! It's called GRFDiff, and you use it like this:
grfdiff trg1.bak trg1.grfHere, trg1.bak is a backup copy of the original GRF file. GRFCodec should have made it during step 3. Once it exists, GRFCodec won't touch it again, so it'll always remain the original copy.
Now what this command does, is take all the sprites that are new and put them in a file called trg1.grd. This file should be fairly small, so that you can easily send it to your friend. What your friend then has to do is run GRFMerge like this:
grfmerge trg1.grdThat will integrate your changes into his trg1.grf, and everyone will be happy.
Unless he doesn't have GRFMerge...
...in that case, you can instead tell GRFDiff to make a self-extracting file. That means it turns the GRD file into a program, which you can run instead of GRFMerge. To do that, run
grfdiff -x trg1.bak trg1.grf -o yourmod.exeThat will make yourmod.exe, or any other name you give it. Be creative, and make the name relevant to what you actually changed.
Then simply send out yourmod.exe, and tell people to copy it to their TTD folders and run it. Tadaa! They've got your modified sprites.
If you want to make your .exe file compatible with both the DOS and the Windows version of the game, you of course need to edit both trg1.grf and trg1r.grf. Then you combine the changes from both files into one executable like this:
grfdiff -x -o yourmod.exe trg1.bak trg1.grf + trg1r.bak trg1r.grf
By specifying the plus sign between two sets of files, you tell GRFDiff to take the changes from both sets and make a single output file, yourmod.exe.
When run, yourmod.exe will patch either both of the files if they are installed, or otherwise it will just skip those that it can't find. That way, it'll work no matter whether the DOS or the Windows version is installed, or even if both are present.
Easy, wasn't it?