Resolution and scaling

Not sure if this is an issue but I have a screenshot. I added the white border.

The image has a black border when taking screenshots. I am working on all the thumbnail titles for the BBC Micro with all the screenshots taken from bbcmicro .co.uk
(I was working on getting permission to use all the screenshots from the site the last few days and was given the go ahead, so once the Titles are done I will have a repository)

Where I am at with it is I can keep the borders, autocrop with imagemagik when taking them, or open an issue and see if there is a scaling option that might make sense for the code.

I am open to suggestions.

Edit: This is not correct yet due to various modes. brb.

This how I am converting my title screen screenshots.
mogrify -resize 640!x512! -quality 95 "${dest_dir}/${is_titlepng}/${fname_new}"
mogrify -crop 558x456+41+37 -resize 512!x410! -depth 4 -type optimize -alpha off -quality 95 "${dest_dir}/${is_titlepng}/${fname_new}"

Should mostly work fine with convert as well. Both are from imagemagik.

I preempt my crop with a forced scale of 640!x512!
I keep the 1 pixel ring around it that png uses as a "blur" as an fyi if there is to be a code update. It would be 556x454+42+38 as actual screen. 42x38 marks top left corner to begin crop and then it is the number of pixels to keep 556x454.

So where I am at is I can crop fine on some modes and some I cannot.
There is remove black border in the tools but that will really mess up some images I believe.

The image sizes all come out the same size so I cannot work off of that.
Border sizes appear variable depending on mode. So I am thinking for a bit.

[zoltanvb]

There are multiple solutions I can think of. From consistency point of view, it would probably be better if the active video area can be determined exactly, and then border size can be configurable on top of that, currently there is no such logic, but it can be added.

I wonder if this data is correct? https://www.dfstudios.co.uk/articles/retro-computing/bbc-micro-screen-formats/

The other solution would be a kind of "intelligent zoom" what is available in ep128emu-core: at the press of the button, the screen would be cropped to a rectangular area which is not border-coloured. It requires user interaction, but at least I found it to be handy.

I have a fork but that is not going to be current until I figure some things out.
I was able to get it to compile.

For my purposes, if I can be pointed to where the SDL initializes and how to set a background color not part of the palette I should be able to use it as a crop method (some shade of gray). I figure it will take a month or more to get through all the titles, but I can get rolling on those. I will update if I can get this part figured out.

I did play around with other changes and managed to break some things on my end, so I might make some progress down the road with the scaling.

[zoltanvb]

On second read, I do not completely get the part around coordinates.
Core currently outputs 736x288 always, with a screen aspect ratio of 4:3 (i.e. non-square pixels). If you are taking screenshots with scaling/shaders, resolution will be different, but I'm not sure that is practical for thumbnail creation.
Border size may be different in each modes. I am not very familiar with the BBC Micro itself, tried to check if there is a way to set border color for a quick test (like on other 8-bit machines), but maybe there isn't.

The libretro core does not use SDL, the framebuffer is handled directly.

I think the background color is not easily changeable, I could be wrong, but have issues there. What I went with

mogrify -bordercolor black -fuzz 20% -trim -quality 95 "${dest_dir}/${is_titlepng}/${fname_new}"
mogrify -resize '640x^>' -gravity center -background black -extent 640^x256^ -quality 95 "${dest_dir}/${is_titlepng}/${fname_new}"			
mogrify -resize 512!x410! -depth 4 -type optimize -alpha off -quality 95 "${dest_dir}/${is_titlepng}/${fname_new}"

This works fine for what I am doing. I run into an issue with Boffin gameplay which is set to 736x. Not a big deal, seems really rare and I can accommodate on my end. Besides, I will just be doing the titles and seems pretty straightforward.

The issue can close if you want. I figure screen resolution is already a consideration for the code.

Edit: 512x410 is the images coming from bbcmicro dropped from 640 so I want them matched.

[zoltanvb]

From my side, this can remain open, it serves as a reminder to implement border setting, it is a nice improvement for gaming experience.