Amiga Extra Half-Brite mode support?

Hi there Cosmigo, I would love to see Pro Motion get support for the Amiga’s Extra Half Brite/Bright mode. (For those who don’t know what EHB mode is, please check out the link below for a good explanation.)

Right now the only way to get “Half Bright” colours in Pro Motion is to make a duplicate of your colours and batch modify them in the ‘Multi Color HSBC’ tab in the Color Palette Window’, by dragging the ‘B’ slider down to -50. This works okay, as long as the original colours have RGB values that are even numbers. Odd numbers get rounded up, whereas the Amiga hardware/software rounds them down. This means the colours generated in this way are ever so slightly off. Which becomes very noticeable in the Amiga’s 4 Channel Bit Depth.

It would be great if the math was compatible with how the Amiga generated the Half-Bright colours.
Cherry on the top would be if EHB generation was done dynamically/on-the-fly. So that any changes made to the source 32 colours are updated to the EHB colours in real time.
The Grafx2 app has an EHB feature, but you have to press a button to (re)-generate them each time you modify a colour.

Here is a good write-up explaining exactly what Extra Half-Brite is.

https://amiga.lychesis.net/knowledge/EHB

That link didn’t work for me. I had to trim it back to:
https://amiga.lychesis.net/knowledge/EHB.html

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Ah… I see. Thank you Zodman, for letting me know and providing a correct link. I’ll update my post. :+1:

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Thanks for the link though; I’m a huge Amiga fan and had no idea this existed!

This task seems something that could (and probably should) be done via a custom plugin that manipulates the current palette to obtain exactly the results you’re asking for. The plugin will have to convert the RGB colors into some other color system before the half-brightness manipulation (well described in the article you linked, i.e. a mere bitwise-shift to the right of RGB colors express as percentages). It should be fairly straightforward to reproduce the exact algorithm used by the Amiga.

Having such features in custom plug-ins prevents bloating the application with native features which might not be used by all — which is the reason the plug-ins interface was created in the first place. Also, a custom plug-in would allow a fine-tuned implementation according to needs, and allow others to create variations thereof that might work best for their own uses.

That being said, it would be nice if PMNG would support some sort of internal scripting for manipulating the palette and transform colors in a simple way. This feature request has come up in various forms in the course of time, delineating a general need for an automated way to process colors according to custom rules, e.g. to generate color ramps, color schemes, etc.

If I remember correctly, there is already a feature which allows some degree of control in color manipulations via expressions, but I’m not sure about the details and couldn’t find it in the online documentation.