Splash image in Redhat/CentOS installer is present in isolinux directory.
isolinux/splash.lss
The graphic is in a somewhat odd format, called LSS16. As the name indicates, it is limited to 16 colors. To edit the graphic, first convert it to a PPM:
lss16toppm < splash.lss > splash.ppm
Its better to use new .gif image.
Next, edit the file using The Gimp. Save the resulting file as an indexed gif withno more than 14 colors (plus black and white, for a total of 16).
To set the maximum number of colours – goto the Image Menu —>Mode—>Indexed option. Change the maximum number of colors to 14 and click on theConvert button (although convert.exe (ImageMagick tool) can also be used to limit the maximum number of colours to 14 – the palette will not be optimised and the image is likely to be of poor quality. Using GIMP as outlined above will result in a much better image).
Then, convert the file to a pnm/ppm:
giftopnm < splash.gif > splash.ppm
Before taking the next step and converting the ppm file to an LSS, ensure that the LANG environment variable is set to en_US. RedHat 9’s default LANG variable is en_US.UTF-8, which will cause the LSS conversion to fail. To actually convert the ppm to a n lss, use this command:
ppmtolss16 < splash.ppm > splash.lss