Astronomy-focused Python tool with a GUI to prepare texture maps of celestial bodies. The program automates common texture actions, most of which can't be found in graphics editors, such as reprojection and color/albedo calibration.

CTC may be considered as a complement to the capabilities of TrueColorTools: you can copy the calculated color (with gamma correction disabled in TCT) and calibrate the texture using it.

Installation

Running through Python

Cylindrical Texture Calibrator has been tested on Windows 10/11, macOS and Linux (this can be used to run on Windows 7). Python version 3.10 or higher is required. Depending on the system, you may need to replace the python command with python3.

1. Clone the repository or download the archive using the GitHub web interface;
2. Open the console in the project root folder;
3. Create a virtual environment with python -m venv .venv;
4. Install the dependencies with .venv/bin/pip install -r requirements.txt;
5. Execute .venv/bin/python -u runCTC.py.

Executable file

SevenSpheres compiles stable versions of CTC for Windows 8/10/11. Thus, Python is not required in this installation way.

1. Go to the latest release page;
2. Download and unpack the first archive;
3. Launch the runCTC.exe.

Notes

• The operations are applied to the image exactly in the order in which they are listed.
• In calibration, the alpha channel is considered a mask. That is, transparent places do not affect the result.
• Albedo and color calibration use a precise formula to calculate mean brightness that accounts for the distortions of planetographic projection.
• The albedo calibration is actually a green channel calibration. This is the best approximation that can be made without other spectral data.
• Why are reprojections only available to planetographic projection? In the Celestia space simulator this is the projection used for spheroids (for 3D models it is the planetocentric projection).
• Cyclic longitude shift uses the Fourier transform, and as a consequence is subpixelized.
• Gamma correction is an image transformation that lightens shadows and lowers contrast. It is needed to simulate the similar effect of the human eye. Household photos automatically apply gamma correction, but space images only occasionally take it into account. If in doubt which checkbox from the two to choose, choose the CIE sRGB, it works better in shadows.
• To de-apply standard gamma correction, you can use "Apply custom gamma correction" item with value 2.2. But note that every gamma correction operation results in data loss.

My thanks to arbodox for the creation of the project logo.