pthumb / image+ bug(?) - output height in pixels sometimes gives offset of 1 pixel

Hi,
When using pthumb to output images with fixed size sometimes the result differs by 1 pixel.
I ask for image height of 400px, and some images always result in 399px.
I could not detect the difference in the source images which cause this - I assume some rounding of aspect ratio...
I changed to image+ but I get the same behavior.

pthumb:


image+:
Target (minimal) Width: 400
Target (minimal) Height: 270

Output as Image+, Generate Thumb URL: yes, not custom output chunk

My temporary solution using image+ is to re-crop it with a very small change - the recalculation usually fixes it and the image output size is as expected.

Since I have an image list with float left, a 1-pixel change in height breaks the entire grid.
Did anyone else encounter this and have a solution?

I would like to avoid any of the following solutions I thought of:
- have the image as a CSS background (bad for SEO)
- have the image with fixed width height according to the breakpoint (not responsive as I would like)
- CSS object fit (best solution I found but a problem with browser support)

I think this may be a browser bug. I've read of cases where image heights in Firefox are often 1 pixel different from those in Chrome. I'm not sure if that's still true, but you might check in different browsers.

thanks for your answer.
I'm not sure I agree - but thankfully I could not recreate it to test on firefox vs chrome.

Please see attached screenshot - in the devtools it was written Natural: 400px,
and for one image for no clear reason Natural: 399px

My understanding was the source image is generated by the pthumb resizer.
Next time it happens I will try to save locally the image from multiple browsers
and see in photoshop if browsers are related to it.

Uploading screenshots doesn't work right now, so you have to put them somewhere else and provide a link to them.