Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

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by mhr
09 Sep 2013, 03:31
Forum: Tutorials/How-To's
Topic: Dewarping with a regular calibration point grid
Replies: 18
Views: 20416

Re: Dewarping with a regular calibration point grid

Just homogene gray is fine. The gray card should fill the whole area of interest (and a bit more). If the options -nx and -ny are specified, a local varying correction based on a gray color grid of the calibration input is used to correct spatially varying color (e.g. due to uneven lighting conditio...
by mhr
05 Sep 2013, 12:36
Forum: Tutorials/How-To's
Topic: Dewarping with a regular calibration point grid
Replies: 18
Views: 20416

Re: Dewarping with a regular calibration point grid

In Microsoft Visual Studio there is a Batchfile called 'vcvarsall.bat' This can be called within a console 'cmd.exe' to set up all variables to compile on the command line. The files can be compiled with a command like cl /Ox ppmunwarp.cc ppmroselib.cc cl /Ox ppmwhitebalance.cc ppmroselib.cc Anyway,...
by mhr
04 Sep 2013, 17:14
Forum: Tutorials/How-To's
Topic: Dewarping with a regular calibration point grid
Replies: 18
Views: 20416

Re: Dewarping with a regular calibration point grid

Hier is version 1.5 of the programs. ppmwhitebalance was enhanced to accept a rectangle by using the new options -gx , -gy , -gw and -gh . The rectangle should roughly specify the area of the gray card in the picture. Outside the rectange, the gray card pixels are set to the mean color value from th...
by mhr
31 Aug 2013, 17:31
Forum: Tutorials/How-To's
Topic: Grid based white balancing of images
Replies: 9
Views: 6760

Re: Grid based white balancing of images

I joined common parts of ppmunwarp and ppmwhitebalance into a library to eliminate code duplicity.
Version 1.4 can be obtained in the thread http://www.diybookscanner.org/forum/vie ... =19&t=2589
as it is now bundled with ppmunwarp and the latter is discussed in the above thread.
by mhr
31 Aug 2013, 17:28
Forum: Tutorials/How-To's
Topic: Dewarping with a regular calibration point grid
Replies: 18
Views: 20416

Re: Dewarping with a regular calibration point grid

I splitted the identical parts of the programs ppmunwarp and ppmwhitebalancing into a library and eliminated a bug in ppmunwarp due to regression (version 1.0 was not affected). Here are both programs in version 1.4 together with the library and a primitive makefile. Just drop the .txt ending as alw...
by mhr
31 Aug 2013, 17:18
Forum: Tutorials/How-To's
Topic: Dewarping with a regular calibration point grid
Replies: 18
Views: 20416

Re: Dewarping with a regular calibration point grid

Hello abmartin , nice to see that my program is useful for You! Actually I discarded the idea of a curved scanning rig a while ago. It was based on an erroneous idea about depth of field. So I use a flat platen as all others also do. I have a one camera setup with fixed geometry between camera and p...
by mhr
27 Aug 2013, 07:50
Forum: Programs, Software releases, and more.
Topic: Scantailor preprocess script
Replies: 30
Views: 18490

Re: Scantailor preprocess script

New versions 1.3 of ppmunwarp and ppmwhitebalance are available in the above mentioned tutorials.
They are capable of converting any raw ppm file now, including ones with 16 bit color depth. You can create such
files via e.g. dcraw from raw camera images.
by mhr
27 Aug 2013, 07:42
Forum: Tutorials/How-To's
Topic: Grid based white balancing of images
Replies: 9
Views: 6760

Re: Grid based white balancing of images

I just decided to enable ppmwhitebalance to be able to convert 8 bit and 16 bit ppm files. So this version 1.3 of ppmwhitebalance should recognize and convert all valid raw ppm files. You can create 16 bit ppm files from raw camera dng files via a program like dcraw . The target color depth can be s...
by mhr
27 Aug 2013, 07:39
Forum: Tutorials/How-To's
Topic: Dewarping with a regular calibration point grid
Replies: 18
Views: 20416

Re: Dewarping with a regular calibration point grid

I just decided to enable ppmunwarp to be able to convert 8 bit and 16 bit ppm files. So this version 1.3 of ppmunwarp should recognize and convert all valid raw ppm files. You can create 16 bit ppm files from raw camera dng files via a program like dcraw . The target color depth can be specified wit...
by mhr
16 Aug 2013, 09:19
Forum: Programs, Software releases, and more.
Topic: Scantailor preprocess script
Replies: 30
Views: 18490

Re: Scantailor preprocess script

There is another update of ppmunwarp to version 1.2 in http://www.diybookscanner.org/forum/viewtopic.php?f=19&t=2589 , which eliminates a minor bug in option processing. This last version is used in a tutorial, which I have written today about a new tool for white balancing color correction. The new...