The source code of Adobe Photoshop v. 1.07 has been released by the Computer History Museum in Mountain View and can be downloaded at: Adobe Photoshop Source Code
Rosa Menkmans website “beyond resolution” presents her artistic research which she terms “Resolution Studies”. The section on the Genealogy contains a discussion of the practices and politics of test images in which she touches on Photoshop as well. ▋▅▉▝▊ || beyond resolution