A few times now, I’ve run into a bug, or a piece of strange behavior, that should probs be changed if it can: Discourse lightboxes images, but there appears to be a lower limit on the resolution for which images get lightboxed. That’s fine enough – you wouldn’t want small inline images (like, say, 
, or 
) to pop up bulky caption bars when you mouse over them. The issue, however, is that this limit is set far too high, which causes formatting issues when images of different resolutions are mixed.
The issue is twofold: ① The images don’t show up in the image browser (i.e. if you’ve clicked on a lightbox image, pressing left or right will skip past the non-lightboxed ones), and ② more importantly, there’s a vertical formatting issue when placing a non-lightboxed image next to a lightboxed one. Take a look at these two examples:
The lower limit for lightboxing appears to be 501 pixels in height (or you could call it an upper limit of 500 pixels for non-lightboxed images), with no limit for the width. Some examples – note that #2 and #4 are clickable, while #1 and #3 aren’t:
To be useful, this limit should probably be set far lower – perhaps at the 149–150-pixel boundary or so – lest it cause issues with low-res screenshots and sundry images found around the corners of the internet.
Apparently, there’s a setting called “max image height” that can be adjusted to change this, but I think that’d cause images to be limited to, say, 150 pixels in height in the post? This might be an issue I have to report to Discourse.
In the case that this can’t be fixed without an upstream change, I should note that although it won’t be applicable to all images, in the case of screenshots, you can use Discourse’s [grid][/grid] tag to at least display them correctly in the post – but the lower-res images still won’t be clickable or appear in the lightbox pop-over:
