You are inquisitive and well ..
Everything that was previously written is true
What is missing, however, is the proverbial dot over and ...
I don't know if I can write precisely in this foreign language ..
Let's start with this -> my first 3K map had 25 GB - png format (it was the first such a large map after allowing the dimensions 3135 x 2975) and I sent this one to be placed in Map Finder
Of course I got a reprimand ... ....
Then I found out that pictures placed on the server in MF - must have certain parameters.
I also learned how Luis checks and adjusts the drawings before going to MF
Let's call it - the boundary / impassable conditions that condition the file in jpg format
We also know that MF is only available for downloading maps manually
It used to be the only available map source. Now it is active under certain conditions ...
Currently, all the traffic related to the maps for the game has been taken over by other servers
Only the map in jpg format can be downloaded automatically.
To meet expectations - I prepare my jpg files exactly as Luis does - when converting png -> jpg
Now, after this introduction, which is important to understand why I am making my maps this way, let's go to the point
If you are making a map ..
and the input material is 24-32 bit color
the program is also 32 bit color (the previous version of Gimp had no choice - the current one has the option to choose the color depth -> 8, 24, 32)
.. then the output was 24 bit color for the png file
So it was necessary to generate an 8 bit color png file
From this file, Luis obtained a jpg file
The quality of this jpg file and the weight was worse than the jpg file (my file)generated directly from 24 bit color (with the same conversion parameters)
It is different if you are using 8-bit material and working in an 8-bit program. Then it doesn't matter -> you can send the png file to Luis. After generating the jpg file (according to the procedure) you will get the same jpg file that Luis will generate. Of course, your png as a non-lossy format - especially when zoomed in, it will look sharper than jpg.
But it doesn't change anything -> players will get a jpg file (it will download automatically), and who is playing on the map enlarged by 300%?
Yes I know - people have such small monitors - they want to see the units .. .. -> but they have a jpg file - as a map
And now finally - what you presented above ..
The 778 map was indexed color, and that is the problem
If you use other colors than they were on this map -> outside the range of indexed colors then ..
eg you had a drawing and 240 colors were used there
When drawing, you will use other 20 colors
Total 260 distinct colors
There are only 256 colors in an 8 bit file
So 4 colors will be removed (replaced)
You'll send this file to Luis
Luis converts it to jpg using -> JPEG, quality: 70, subsampling ON (2x2) (these are the - quality boundary parameters)
All players will get such a map ..
As I wrote
"To meet expectations - I prepare my jpg files exactly like Luis does - when converting png -> jpg"
He considers this on the basis of what the player will get
For files at least 24 bits - making a jpg file yourself - is a positive thing (all the maps that I have made from scratch)
For 8-bit files - it does not matter
For files produced as a mixture (indexed colors + other materials) it can be on + or neutral
If you use a png or jpg (8 -bit) file as input -> then looking at the result -> jpg file for the player -> it doesn't matter