"Like, let's say I want to write a tool that will let me take photos, resize them, crop them, add watermarks. I don't even... where do you start?" I would sugg

"Like, let's say I want to write a tool that will let me take photos, resize them, crop them, add watermarks. I don't even... where do you start?" I would suggest perusing materials of a computer graphics course. For instance, this course from Brown seems to have lecture notes online: http://cs.brown.edu/courses/cs123/lectures.html http://cs.brown.edu/courses/cs123/lectures.html http://cs.brown.edu/courses/cs123/lectures/CS123.08_Image_Processing_IV.09.25.14.pdf http://cs.brown.edu/courses/cs123/lectures/CS123.08_Image_Pr...