What is the best way to auto crop bulk images?

Fast Stone Photo ReSizer has always been my number one choice!

XnView and NConvert are your friends. NConvert is a command-line tool to process images, with resize and crop functionality. XvView is a fast image viewer with batch processing capability. Once you do a crop in XnView, you can have it create a batch file for you that call NConvert on a bunch of images. It can do a lot more than crop at the same time, like resize and sharpen if you need it.

If its the same crop, you can use software like Lightroom to copy the crop (and crop angle) to as many photos as you want.

Photoshop has a function exactly for that:

Scan your cover (you can even scan multiple covers in one scan) In Menu: File > Automate > Crop and Straighten Photos

It automatically crop and fix the rotation of the photos in the current file. If multiple photos are found in the image, it will automatically split in several files. If you have ton of them, you can create actions to have the Crop and Straighten done on each of them in batch.

ImageMagick, using the -trim operator. See: http://www.imagemagick.org/Usage/crop/#trim.

ImageMagick is free (and open source), and you can get pre-built binaries for Mac OS, Windows, or Unix from http://www.imagemagick.org/script/download.php .

Another suggestion: Phatch, a photo batch processor that, among lots of other things, does cropping.

PHOTOSHOP ACTION

1. Open Adobe Photoshop
2. Open Image
3. Select Windows -> Actions, then click "New Action". Press OK.
4. Crop photo.
5. Stop Action Recording
6. Go to File-> Batch -> Choose Folder. Press OK.

After having to Google this issue myself, I decided to write some instructions on how to do this with either Adobe Photoshop (if you already have that), or with GIMP (for free).

GIMP turned out to work better in my case. Complete easy-to-follow instructions can be found here:

• How to batch separate & crop multiple scanned photos

This works for single scanned book covers (as in your case), or even with multiple images. Success!

Scanning books or their dust jackets? I imagine the scanner lid won't close properly with a book under it, in most types of scanners. One option: Photograph the books with a DSLR or other digital camera, and use a program to auto-crop them. This way you could even crop two or more books at a time, speeding up things.

Programs for image cropping and document cropping are different. The former detect images' edges and discard the scan's background; the latter detect page edges and crop along those. OP wants to crop scans of book covers, which are akin to images - so an image scanner is needed.

Also, if you have multiple scans, each containing one or more images, it'd be nicer to crop them all with one click. In Photoshop, you could do this by doing File > Automate > Crop & straighten on the whole batch, with a script like this. If you're not au fait with scripts, Snip app for Mac does the same thing (There's another similarly named app, SnipTag, for automatically batch-cropping scans and editing image metadata, but that's outwith what OP asked.) [Disclosure: I do customer service at AIL, developer of these apps.]