Ratio of transformedSrc upon only specifying one dimension

[seop]

I wonder if it is guaranteed to have the original source's ratio of the image when I only supply the maxWidth or maxHeight to transformedSrc.

So far, I have noticed that the transformed image has the same ratio, but because I do not know the exact technology behind it, I am not so sure if I can assume that its ratio is always the same (meaning, none of the image is cropped while transforming).