[MapServer-users] How to use OPACITY and COLOR in STYLE for raster float32 data

[Trygve Aspenes]

I have raster data with float32 data.

To colorize this I have defined several CLASSES each with a STYLE for a 
specific interval of float values.

eg:
        CLASS
             NAME "no meassure"
             GROUP "this-palette"
             EXPRESSION ([pixel] >= 0 and [pixel] < 0.03)
             STYLE
                 COLOR 190 190 190
                 OPACITY 5
             END # STYLE
         END # CLASS
and onvards for increasing pixel values.

This works ok, but I dont understand what happens to this color (as 
given in the CLASS above) in the resulting png image from a getMap 
request.

The provided link is the png produced by a getMap request with the given 
style.
If you look closely the large area between the bluish areas should have 
the style as given above. However if I display the image with display 
these pixels have values 54 54 54 0.129412

https://drive.google.com/file/d/1pof5BQoR3vzIo6KRvOmEtjgBMeZehCy_/view?usp=sharing

(just clicking the link will not show this I think, you have to download 
it and view it in some viewer which can provide pixel details or a 
screenshot is provided here 
https://drive.google.com/file/d/1IOgkvwCtfHAEL2jCGhe9arhoI26D-MRV/view?usp=sharing

So my question is: How on earth can the given style with color 190 190 
190 and opacity 5 become 54 54 54 0.129412?

Opacity is a integer between 0 and 100 ( as in percent?) and some 
scaling is done by the mapserver code to get to alpha (between 0 and 
255) 
https://github.com/MapServer/MapServer/blob/main/src/mapfile.c#L2797-L2806

But If I give Opacity 5 I would expect to get something like 0.02.

Trygve