Resolution patcher for Anno 1503

A simple Python script which patches the game “Anno 1503” to run at higher resolutions. To do so it has to replace one of the available default resolutions.

Running

You need Python 3 to run the script. I have tested it with Python 3.11, but it should run on 3.9 or higher as well. There are no additional dependencies for running.

Here is an example invocation on Unix with the game installed through Wine:

# Patch the game to the default resolution 1600x900 in current directory
./anno-1503-resolution-patcher.py

# Specify resolution and game path explicitly
./anno-1503-resolution-patcher.py -x 1600 -y 900 '~/.wine/drive_c/GOG Games/Anno 1503 AD'

# To see full instructions and a list of know working resolutions run this
./anno-1503-resolution-patcher.py --help

The patcher should work on Windows as well, but I have not been able to try it out. Running the script will produce one or more patched DLL files and a patched text file. You have to swap out the files yourself. Only one patched DLL file will actually work. Here are the files which will be patched and need to be replaced:

AnnoFrame.dll
Texte.dat

Why it is so complicated

The script is looking for a byte pattern which matches the existing resolution. However, there can be multiple matches for the pattern and the offset in the DLL varies depending on which build of the game you have. Therefore it is impossible (at least with this naive approach) to know which patten is the one to replace. I took the safe route of creating all possible replacements and offloading the verification work onto the user.

If anyone can figure out a more reliable way please let me know.

How it works

See the comment at the bottom of the source code.

License

Released under the MIT-0 license. See the LICENSE file for details. This is as close to a “Do whatever you want” license as it gets. This code exists primarily for posterity and reproducibility.

Acknowledgement

A patched DLL was provided by user millimarg from the Annozone forums. In a subsequent post he explained how he created the patch, albeit in German. I have created this patcher script for posterity, both to document how it works and to provide a reproducible method of creating your own patch in case the download to the original patch ever gets lost.