[leejoramo]

Much of Photoshop's interface came from Apple's own MacPaint which shipped at the launch of Macintosh:

https://en.wikipedia.org/wiki/File:MacpaintWP.png

http://www.folklore.org/StoryView.py?project=Macintosh&s...

[ConstantineXVI]

Coincidentally, the CHM has MacPaint's source[0] as well.

(I've honestly not heard much about CHM before. Making sure to find my way there next time I manage to end up in the Bay Area)

[0] http://www.computerhistory.org/atchm/macpaint-and-quickdraw-...