This can easily be automated in Photoshop.
Before you begin make sure all your 4 x 6 images are in one folder, and take a note of the folder location. You may wish to split up the job using several different folders, as this will generate lots of new documents, especially if you have 300 photos!
Click File > Automate > Contact Sheet II
Choose the folder ...
Here's a modified version. This will scan subfolders for jpeg files (line 28), save a panorama with a name of the first jpeg file + -pano and will remove the jpeg files in the end:
var runphotomergeFromScript = true; // must be before Photomerge include
//@includepath "/C/Program Files/Adobe/Adobe Photoshop CC 2019/Presets/Scripts/"
There is a way to do this. It's takes a few steps, but can easily be recorded as an action.
Photoshop doesn't support HSL color natively, so first of all you need to download and install the HSB/HSL Filter from Adobe's site.
The filter changes an ordinary RGB image so the red, green and blue channels represent hue, saturation and lightness instead. It will ...
Duplicate your layer (this is destructive)
Filter > Other > HSB/HSL
Input RGB, Row Order HSB or HSL (up to you)
The image will now look distorted as the R, G & B channels are represented as H, S, L/B respectively
Invert the Green (now Saturation) channel
Select RGB (all) channels
Convert back to RGB using the same filter, just reversed (...