I am designing a system that will scan in standardized forms to images (e.g., TBitmap). I would like to identify alignment marks on these pages and use the locations of these crop marks to rotate the page to its proper orientation (so top is actually up) and to crop the image to the location of the alignment marks.

An example image of a typical mark I'd need to locate is:

[![Crop mark](https://i.stack.imgur.com/Y03RE.jpg)](https://i.stack.imgur.com/Y03RE.jpg)  

(source: [tpub.com](http://draftingmanuals.tpub.com/14065/img/14065_69_1.jpg))

What are techniques to evaluate an image obtained from a scanner to locate various marks within the image? I'd need to locate multiple marks and their center point locations.