Applying transformations to NSBitmapImageRep

So ... I have an image loaded into an NSBitmapImageRep object, so I am able to examine the contents of specific pixels via a two dimensional array. Now I want to apply a couple of "transformations" to the image, in preparation for some additional processing. If I was manipulating the image manually, in Photoshop, I would:

1. Rotate the image
2. Crop a portion of it and discard the rest
3. Apply a "threshold" transformation (which essentially converts the image to black and white, based on the threshold value I provide)
4. Resample the image to shrink it down a bit (which, although losing some image quality, will speed up the subsequent processing)

(not necessarily in that order)

Are there objec开发者_开发百科tive C methods available to facilitate these specific image manipulations, with the data in the NSBitmapImageRep object? If so, can someone point me to some good examples?

Create a CIImage for the CGImage of the bitmap image rep. Then you can:

1. Rotate it
2. Crop it
3. Apply a threshold filter
4. Scale it