Crop to visible

[Max17]

I love using XnView Classic to make thumbnails for my YouTube videos. My usual process is to capture a screen grab from my video in VLC Media Player which creates a .png file of the screen. I then:
1) open the .png file in XnView Classic,
2) zoom in,
3) scroll up/down and sideways to frame the view that I want,
4) selelect what is visible with my mouse,
5) click the Crop button, and
6) save the file as a .jpg.

The problem is that I don't always select the exact edges of what is showing in my zoomed in window view. This results in a file that is slightly shorter or narrower than the original aspect ratio and results in a thin black bar in the YouTube thumbnail. It would be great if there was a button or keyboard combination that could crop to the exact dimensions and location of what is currently displayed. I have read very many of the foumn discussions but I haven't found anything like this.

Would this be possible to implement?

[user0]

I see no reason for 'Select visible' command

use 'Custom selection...' in Edit > Set selection ratio
OR
Crop panel (Shift+X w/o selection) in XnView MP

[Max17]

I don't have XnView MP so that isn't an option for me. Maybe I will look into it.

Your other suggestion accomplishes exactly what I want. The extra advantage is that it allows infinite zooming (instead of by steps with the mouse wheel) so that perfect framing and cropping can more easily be achieved. A disadvantage would be that it is an extra step that must be reapplied for each new image opened and I sometimes want to crop several scenes and then choose which one looks best in thumbnail size. I thought I would need to select Edit>Set Selection ratio>Same as image for each new file but I see the keyboard shortcut "D" does exactly what I want without going into a menu each time.

Thanks!