On Thu, 2020-01-30 at 20:44 +0100, geop wrote:

I have scanned photographs which have a white border. I try "Crop to content"

Crop to content removes outside borders of picels which all have exactly the same value but your border, although whiteish, is not like that.

Rotate the image -- the easiest and fastest way is to use tool options, turn on reverse/corrective mode, and turn on a grid "number of lines", and change the number of lines until one lines up with the a vertical edge in the border; drag the lines to rotate them a little and get the grid line to match as well as possible, and then in case the image isn't actually perfectly square, repeat for the top and bottom inner border edges, then finally press Enter to do the rotation.

Then crop the iamge with the crop tool to get rid of the border, if that's what you want, or to keep it, image->flatten image, then use rectangle select to select the inner pictiure, select->invert to change it to select the border, select->feather by 5px or so to make the edge soft, and drag the white swatch from the toolbox into the selection (if you don't have the default black and white, press d or click the black/white icon that's near the swatch).

slave

PS: clean the prints with a microfibre cloth, and the top of the scanner with that and eyeglass cleaner )spray onto the cloth of course, notthe scanner, and not the same cloth you use for prints; you can also use a special Japanese roller that was made for cleaning gramaphone records, https://amzn.to/2U9jN3R - but i worry that it may lift the surface of the print.

Liam Quin - web slave for https://www.fromoldbooks.org/
with fabulous vintage art and fascinating texts to read.
Click here to have the slave beaten.

On Thu, 2020-01-30 at 23:09 +0100, geop wrote:

So maybe I can suggest (somewhere) to the developers to add some parameters that
permit some range in values for the border color in "Crop to content".

Once you do this you start eating into the main image, but it might be an interesting option to have a "shrink wrap" option in rectangle select or image crop, with a tolerance. Maybe there's already a script or plugin that does this.

Auto white balance loses a little bit of detail. I'm not sure whether rawtherapee or darktable has a way to do this - i tend to scan in 16bit greyscale for things like this (although scanning in colour can make it easier to remove dirt using the mono mixer and choosing blue and/or green channels). Bt i'musually scanning to sell the pictures on fromoldbooks.org.

The scanner i have came with holders for film strips and software for Windows (silverfast i think) that knew about the holders and identified all the photos automatically, a huge time saver.

If you can do a little scriptng you could maybe simply take a sample of the middle of the image, use that for white balance, and then undo (in the script) and apply the settings to the whole image.

It seems likely someone else has already done this, too...

slave

Liam Quin - web slave for https://www.fromoldbooks.org/
with fabulous vintage art and fascinating texts to read.
Click here to have the slave rewarded with extra work.

On 1/30/20 1:44 PM, Liam Quin wrote:

On Thu, 2020-01-30 at 20:44 +0100, geop wrote:

I have scanned photographs which have a white border. I try "Crop to content"

Crop to content removes outside borders of picels which all have exactly the same value but your border, although whiteish, is not like that.

Rotate the image -- the easiest and fastest way is to use tool options, turn on reverse/corrective mode, and turn on a grid "number of lines", and change the number of lines until one lines up with the a vertical edge in the border; drag the lines to rotate them a little and get the grid line to match as well as possible, and then in case the image isn't actually perfectly square, repeat for the top and bottom inner border edges, then finally press Enter to do the rotation.

Then crop the iamge with the crop tool to get rid of the border, if that's what you want, or to keep it, image->flatten image, then use rectangle select to select the inner pictiure, select->invert to change it to select the border, select->feather by 5px or so to make the edge soft, and drag the white swatch from the toolbox into the selection (if you don't have the default black and white, press d or click the black/white icon that's near the swatch).

slave

PS: clean the prints with a microfibre cloth, and the top of the scanner with that and eyeglass cleaner )spray onto the cloth of course, notthe scanner, and not the same cloth you use for prints; you can also use a special Japanese roller that was made for cleaning gramaphone records, https://amzn.to/2U9jN3R - but i worry that it may lift the surface of the print.

This is probably too simple a solution, but... If the images are all the same size, and have roughly the same border, can't you specify a rectangle select of a size slightly smaller to eliminate the border, position it at the proper offset, and crop? Or if the images are different sizes, compute a rectangle for e.g. 98%?

Gary

Hi - thanks for the quick reply. I wondered if it had to do with the slight
non-uniformity of the pixel color in the border. I appreciate all your advice,
but I really wanted an "automatic" process because I have a LOT of these
bordered photos, and hoped to batch process them.

I see what you mean about rotation. My sample image is very slightly rotated,
and I would think my other images all have some version of the same issue. I can
tolerate that as these images are for family archives.

I should have mentioned that my main goal in eliminating the borders was so I
could use, in a batch process, Auto - White Balance to remove color casts from
many of the old B&W or color photos. From experimenting, the white border seemed
to mess this up. Without the border, the White Balance result seemed usually
"good enough" for my purpose.

So maybe I can suggest (somewhere) to the developers to add some parameters that
permit some range in values for the border color in "Crop to content".

Thanks again! I now understand what the issues are.

Depends on your images but you might get away with the old divide-scanned-images script. There are various enhanced versions but the original is worth a try.

Usually as its name, split up a page with several images but a single image works.

Can be used individually or in a batch mode. Quick video demo, duration 2 minutes, using the batch function.

https://youtu.be/Ozc5WnlMnWY

Attachments: * https://www.gimpusers.com/system/attachments/1354/original/DivideScannedImages.scm

rich404 (via www.gimpusers.com/forums)

Liam R E Quin wrote:

On Thu, 2020-01-30 at 23:09 +0100, geop wrote:

So maybe I can suggest (somewhere) to the developers to add some parameters that
permit some range in values for the border color in "Crop to content".

Once you do this you start eating into the main image, but it might be an interesting option to have a "shrink wrap" option in rectangle select or image crop, with a tolerance. Maybe there's already a script or plugin that does this.

I'm no expert, but it seems that it should be possible to use the fuzzy select tool (with adjustable threshold) to select the border, then Select > Invert and Image > Fit Canvas to Selection? Still with the caveat that it may eat into the wanted image.

Mark.

On Fri, 2020-01-31 at 21:47 +0000, gimp-users.mbourne@spamgourmet.com wrote:

I'm no expert, but it seems that it should be possible to use the fuzzy
select tool (with adjustable threshold) to select the border,

With a large enough threshhold to get most of the border this will probably get part of the image inside; in addition, hairs and dirt on the surface of the print make it hard.

It's possible to combine this with select->grow, but that's not really easy to automate.

slave

then
Select > Invert and Image > Fit Canvas to Selection? Still with the caveat that it may eat into the wanted image.

Liam Quin - web slave for https://www.fromoldbooks.org/
with fabulous vintage art and fascinating texts to read.
Click here to have the slave beaten.

Late last night I got the latest version of the script suggested by Rich and
tried it on a dozen color photo scans with borders. Each was left with thin
"white" strips along the sides and top and bottom, mostly thicker at one end
than the other, indicating there was still a little skew left in the images
(though the script does a deskew). I'll need to vary the parameters, and also
try the original version of the script that Rich used.

@geop

The divide scanned images script can use a separate compiled plugin deskew.exe but no guarantee it will work correctly. Even older than the script. I have tried it in Win10 and it does work (I usually use linux)

However going by the sample image, that is not the problem, the actual picture area is not rectangular, if the side is vertical the top is not horizontal. Your scanner has already made a good job of de-skewing. I think you already know this.

If you can get it down to a minimum border, then any excess can be trimmed. Manually it is: Select All - Stroke Selection - Zealous Crop - Select None

I have knocked up a small python script (trim_it.py) to apply that procedure. It trims off about 8 pixels from the edges. Edit the script for more / less. Find bottom of the tools menu.

If you need to batch, then it is either run in command line, or use in the only up-to-date GUI Gimp batch plugin BIMP see: https://alessandrofrancesconi.it/projects/bimp/

Attached the two plugins zipped.

Unzip and put both in C:\Users\"yourname"\AppData\Roaming\GIMP\2.10\plug-ins

Attachments: * https://www.gimpusers.com/system/attachments/1355/original/trim.zip

rich404 (via www.gimpusers.com/forums)