When you insert an image field you have various options for how to resize or crop the images as required to fit the specified dimensions (see screenshot), and in your case it sounds like you want to choose to crop the images so that they are always the same size, resulting in a shortcode something like
That's unexpected, unless your images are smaller than 300px * 300px, as the crop option won't expand the images to fill that size.
Can I take a look at your site to see?
I will mark your next reply as private so that I can get log-in credentials from you—you may want to create a temporary admin user for me to use that you can later delete. And be sure to have a current backup of your site.
Thanks for that, looking at your site I can confirm that the issue is with upscaling small images.
There are essentially two options available when inserting the shortcode for the image, one being to "pad" the image so that the image takes up the designated amount of space on the page even if that means some blank space where the image is too small, the other being to stretch the image to expand to the required size.
But in my testing, I found these only work for custom image sizes (rather than registered sizes such as "medium"), and they also only appear to have an effect on portrait images rather than landscape images.
And what I think you want—to upscale the images without distortion—doesn't appear to be possible at all.
I've escalated this so that I can get some clarification from my colleagues about what is intended and whether that works, and I'll get back to you when they share their findings.
I had confirmation that this is expected, as registered sizes perform cropping/scaling etc. at the time the images are added, and so cropping/scaling is only applied when outputting images in custom sizes which have not already had it applied.
My colleague did identify a minor problem with padding portrait images that is being looked into further, but it doesn't apply in your case where you are dealing with landscape images that are smaller than the size you want to display them at, for which the stretch option will expand the width as required.
