How do i keep the ratio of an image when unwrapping I have an image i would like to use as a label which will be wrapped around a cylindrical object. I would like to keep the image from stretching. If I decrease the radius of the cylinder by scaling down along the x y axis, the image squishes, or stretches if I scale up. I would like to alter the radius of the cylinder, prior to UV unwrapping, to best suit the image's dimensions. How do I go about this if the cylinder is an object that already exists and therefore I cannot determine its radius as I can when I add new one? Or is there another way to go about this?
You can view and change the dimensions of the cylinder in the panel to the right of the 3D viewport, labeled "Transform". You can then calculate a proper diameter and height for the cylinder, using the image dimensions.

In the Dimensions section, set X and Y to the desired diameter of the cylinder, then set Z to the desired height. Press ctrl + A to apply the scale, then scale to whatever size you want.

Lastly, keep in mind that for graphics, if it looks right it's good enough, so you can probably eyeball it and no one will notice.