The following script adjusts the brightness and contrast of an image via COM automation of Adobe Photoshop with Python and the win32com package.
import win32com.client
psApp = win32com.client.Dispatch("Photoshop.Application")
psApp.Open(r"D:\temp\blah.psd") # Opens a PSD file
doc = psApp.Application.ActiveDocument # Get active document object
layer = doc.ArtLayers[0] # Get the bottom-most layer
layer.AdjustBrightnessContrast(20,-15) # Bright +20, Contrast -15
doc.Save()
This comes from http://techarttiki.blogspot.com/2008/08/photoshop-scripting-with-python.html where you can find more excellent examples to automate Adobe Photoshop.