i'd like to scan several hundred of my 4x6 prints (photographs)

in my trials, the orientations of the tiff files end up being slightly off, randomly, by several degrees.

some need to be rotate by +2.3 degrees, others by +3.7, others by -1.2, etc ....

is there way to use gimp (or other linux software) to "automatically" correct the orientation? preferably by batch processing

thanks in advance

mike

On 8/14/06, Olivier Ripoll wrote:

T F wrote:

i'd like to scan several hundred of my 4x6 prints (photographs)

in my trials, the orientations of the tiff files end up being slightly off, randomly, by several degrees.

some need to be rotate by +2.3 degrees, others by +3.7, others by -1.2, etc ....

is there way to use gimp (or other linux software) to "automatically" correct the orientation? preferably by batch processing

thanks in advance

mike

Usually, for batch processing, the advice is to use imagemagick (or garphicsmagick), which should be already present on your system. http://www.imagemagick.org/script/index.php Imagemagick is a collection of small utilities (display, mogrify, convert, etc.). Since you probably do not want to overwrite the original file, what you want is "convert". See the man page here http://www.imagemagick.org/script/convert.php

The gimp solution to batch processing is David's Batch Processor: http://members.ozemail.com.au/~hodsond/dbp.html It should work also fine for you.

Thanks. I'm an avid user of imagmagick. There is no "autorotate" feature, nor does David's.

Best, Mike

T F wrote:

i'd like to scan several hundred of my 4x6 prints (photographs)

in my trials, the orientations of the tiff files end up being slightly off, randomly, by several degrees.

some need to be rotate by +2.3 degrees, others by +3.7, others by -1.2, etc ....

The angle varies from one image (scanned) to the next image. The variation is due to minor misalignments when the original is placed on the platten (by an automatic document feeder).

I was hoping to use someone else's script or plugin that calculates the angle on an image by image basis, and then does the rotation and crop.

If I need to code it myself, I would start by trying something like the following, probably with imagemagick.

1) for speed, reduce image to about 100px per edge 2) edge detect radius=0, which tends to draw a box around the image 3) quantize to 2 colors
4) save as ascii matrix of 0s and 1s 5) work with rows/columns as arrays
6) determine indicies of first 1s
7) calculate slope of least sq line
8) repeat for bottom, top, left, right sides 9) toss out anomolous slopes, avg the rest

To detect the rotation angle, try reading this paper: www.leptonica.com/papers/docskew.pdf

Thanks David. I'm reading it.