I am wondering if there is a cheap photo editing suite out there that can size an image, change the canvas size, give me the histogram, and adjust levels via applescript.
Thanks in advance.
There is the freeware, fast and powerful suite of command-line tools (accesible via “do shell script”) ImageMagick (google for it), the super-scriptable $30 GraphicConverter (google for it), and the groovy and now also freeware Imagine Photo from Yarra Valley Software (google for it).
→ not sure, though, if these will provide the histogram info, or how kind the interface will be to adjust levels…
Thanks jj for describing iMagine Photo as groovy 
iMagine Photo can’t do histograms, though it can return you values for individual pixels, along lines, at points, in a rectangle or oval if that helps in anyway.
iMagine Photo can resize images.
I am not a photoshop user so I am not sure what is meant by the term canvas size, but if it relates to specifying the resolution of the image then iMagine Photo can set the resolution. So you could for example scale your image from 2272x1704 down to 640x480 whilst at the same time reducing the resolution from 300 dpi to 72.
As to adjust levels, once again this might be photoshop terminology, so I am not sure what is meant. But iMagine Photo gives you access to a number of quicktime filter effects, and I have listed a few that might be relevant below:
color tint
RGB balance
brightness and contrast
solarize
The full list and description of filter effects can be found on the following page, the first of the filter effects is about half way down and is called blur.
http://www.yvs.eu.com/documentation/compositioneleme.html
I hope that is helpful.
Kevin