Crop max image dimensions respecting original aspect ratio

Is there a way to specify maximum image dimensions respecting original image aspect? Similar to phpthumb params zc=0&far=0 ?
Now when I specify crop aspect like thumbnail:width=750,height=500,aspect=1.5 portrait image is cropped to that aspect.
When I don’t specify aspect thumbnail:width=750,height=500 portrait image is squeezed to that size.

Can’t figure it out. This is one of reasons we use phpthumb on original file like [[+file_path:phpthumbof=`w=750&h=500&zc=0&far=0`]]
Any idea?

Not specifying an aspect ratio will make it keep the original aspect ratio.

Note that MoreGallery will infer the aspect ratio when you specify a width and a height (tho it should never squeeze - it should be cropping). So what you would need to do to keep the original ratio, is only specify one of them:

thumbnail:width=750

So no way for rescaling entire image to maximum width OR height (like phpthumb zc=0 and far=0), or free crop to width OR height?
Specifying only width makes unreasonably huge portrait images. For example, standard Bootstrap boxed layout has maximum width 1140px, so it’s enought to rescale to that width. But uploading 9:16 portait image would create 1140x2027px image, which is too tall for any device. So we normally rescale to someting like 1140x760px or so.