image manipulation (cropping and MetaData)

[snippsat]

Apparently PIL has been discontinued in 2011

It's Pillow just that it use PIL in import for backward compaltity.

Pillow afraid me a little because it have a lot of dependency and seem not lightweight.. ?

It's lightweight and can do all task you listed.
Example.

>>> from PIL import Image
>>>
>>> img = Image.open('forest.png')

>>> img.get_format_mimetype()
'image/png'

>>> Image.MIME[img.format]
'image/png'

# Cropping
>>> left = 155
... top = 65
... right = 360
... bottom = 270
>>> cr = img.crop((left, top, right, bottom))
>>> cr.show()

For metadata look at Edit Your Photos’ EXIF Data with Python