After one does the installation instructions below, all that is needed is to supply a new Genesis 8 face texture then run the software to generate all Genesis 2 textures.

If using Windows, Windows Subsystem for Linux 2 (WSL2) is needed. This will allow Linux commands in Windows.

How to install WSL2 in Windows:
Run powershell as an administrator by pressing the Windows button, typing "powershell", then right clicking on it and pressing "run as administrator". In powershell, run "wsl --install".

Libpng-dev site
Install by running in a Linux or WSL2 command prompt "sudo apt install libpng-dev".
Note: if using Linux and your Linux distro does not have a libpng-dev version that can be installed with apt install (package manager), compiled versions can be downloaded under "Previous binaries" in the site. E.g., for Ubuntu, go to this page and download the bullseye (stable) amd64 versions of libpng16-16, libpng-tools, and libpng-dev deb files. Install each deb with "sudo apt install ./deb_name.deb" in the order listed in the prior sentence. libpng-dev should then be installed.

Png++ (e.g., version 0.2.9) download.
Place these program files into a directory named "png++" in the base directory of this software.

Imagemagick (if wanting to automatically convert to png images). In Linux, install with "sudo apt install imagemagick".
Seperate scripts are provided for Linux (conv_png.sh) and Windows (conv_png.bat) for the png conversion.
If using WSL2, currently is recommended to use the Windows version of imagemagick. This can be downloaded here. Download the .exe file and open it to install. When it gets to the window "Select Additional Tasks" make sure to have "Install legacy utilities (e.g., convert)" checked.
Possibly there is a way to install imagemagick in WSL2 but in testing "apt install" did not install it (missing package). There are instructions to install it from source code link, but a test did not show the ability to run the "convert" program on jpg files successfully using this method. If wanting to try this source code method, a C compiler is needed for this and can be installed with "sudo apt install build-essential". Using the Windows version is recommened instead of WSL2 version.

Genesis 8 textures (to be converted)
Genesis 2 textures (for reference)
These are not included with the software because their licensing may not allow that.

How to obtain DAZ's genesis textures:

One needs to first download Genesis 8 into DAZ 3D to have the textures availible.

Once downloaded, an example location of Genesis 8 textures is: "C:\Daz 3D\Applications\Data\DAZ 3D\My DAZ 3D Library\Runtime\Textures\DAZ\Characters\Genesis8\FemaleBase".

Alternatively, one can use textures that are created by DAZ 3D's face transfer plugin plugin link.

An example of where those textures may be located is: "C:\Daz 3D\Applications\Data\DAZ 3D\My DAZ 3D Library\Runtime\Textures\user_name\Face Transfer\model_name", where user_name is your username and model_name is your DAZ 3D model name.

The Genesis 8 textures need to be copied into the folder: "input/gen8textures" in the base directory of this software.
The face texture must be converted to a png file and named in the following way:
g8fbasefacemapd_1001.png

The script conv_png.sh (Linux) or conv_png.bat (Windows) is included to perform the jpg file conversion. If using the Windows version, run the script in powershell, not a WSL2 terminal. Place the script into any folder that has files that conversion is wanted to be done on. Run the script to convert all jpg files to png files. If running this script is wanted, imagemagick needs to be installed. In Linux, the script may need to be made executable by running "chmod +x conv_png.sh".

Next, one needs to download Genesis 2 into DAZ 3D for those textures.

Once downloaded, an example location of Genesis 2 textures is: "C:\Daz 3D\Applications\Data\DAZ 3D\My DAZ 3D Library\Runtime\Textures\DAZ\Characters\Genesis2\BaseFemale".

The Genesis 2 textures need to be copied into the folder: "input/gen2textures" in the base directory of this software.

The textures must be converted to png files and named in the following way:
eyes: v5breeeyes7m.png
face: v5breeheadm.png
mouth: v5breeinmouthm.png
limbs: v5breelimbsm.png
torso: v5breetorsom.png

The results of the texture conversion will be in the "output" folder.

Overall, the directories should be set this way:

/input/gen2textures/		# place all gen 2 textures here
/input/gen8textures/		# place all gen 8 textures here
/output/			# where new textures will be output
/png++/				# where png++ files should be placed
/src/				# where source code for project is stored
gen8to2conv			# program to run the software

For each run that new texture conversions are wanted, supply a Genesis 8 face texture which will be used for all Genesis 2 textures to be created.

Run from the base directory of this software:
./gen8to2conv
The software will print the statement "completed" when it has successfully completed running.

Note: this software was compiled on Ubuntu 21.10 with GCC & G++ version 7.5.0. If a different distro is used, e.g., WSL2, it may need to be recompiled to run successfully. See "compiling software" directions below for that.

Some post-processing of the generated images in an image editor by the user may be wanted to customize them based on user preferences. This software aims to do most of the texture conversion work automatically, and allow the user to make any final touches wanted. A known issue is that some lines between face texture sections may not be blended correctly. A blur tool in an image editor (e.g., GIMP) can be used to fix the blending in the textures. Perhaps in the future the software can be programmed to do the blending automatically.

Example use of a blur tool in GIMP: select the region with the area that blending is wanted with the rectangle or free select tool from the left hand menu. Before creating your selection, choose "feather edges" from the left side menu "tool options", and set it to radius 100 (or whatever wanted; this sets blending in the selection). Select from top menu: Filters->Blur->Gaussian Blur. Set size X and Y to value wanted, e.g., 10. One should be able to interactively see the blending in the image before applying the blur. This should produce a color blend effect. There are other methods including changing transparency of copy-and-pasted texture sections to blend regions that can preserve texture details that blurring may reduce.

Color correcting body textures to head colors: the software attempts to sample the colors in the face texture and match the body textures to those colors. However, at times the matching has issues. An image editor can correct the colors in the body images. For example, in GIMP, tools from the tool bar such as Colors->Color Balance, Hue-Saturation, Brightness-Contrast, Levels, and Curves, can adjust colors to the desired levels. Whatever 3d software is used with the model may have options to adjust texture color shading when it is applied to the model also.

Compiling software:

If wanting to do development work one needs G++ on Linux or an equivalent C++ compiler.
Note: this software has only been tested to work in Linux and Windows with WSL2 so far.

G++ can be installed in Linux or WSL2 with "sudo apt install build-essential".

An automated rebuilding and running of the software can be done by running "rebuild.sh" from the base directory in a command prompt.

Notes: this software uses somewhat of a bespoke approach to do the texture conversion. This involves selected image portion rescaling, shifting, etc. Also, the color conversion is based on sampling colors between textures. Results seem decent in tests. Anyone contributing improvements by development to the software is welcome.

Running on Windows without WSL2:

It is not known how to compile or run this software in Windows without WSL2 because the Libpng or Png++ libraries seem to have issue with this. Possibly Libpng with GnuWin32 could be used link. It is unclear if Png++ works on Windows without WSL2. Development is welcome to try to get the software working without WSL2, but perhaps will need recoding the software to not use Png++.

If one is not using WSL2, one may need to specify the library path for Libpng with "-I <Libpng_folderpath>" when compiling.