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

Understand DPI, it affects many things in Scan Tailor

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univurshul
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Understand DPI, it affects many things in Scan Tailor

Post by univurshul » 06 Aug 2010, 15:44

UPDATED 8/07/10: This issue has been solved. But it's an important and very straightforward approach if you're miss-understanding DPI setting in Scan Tailor

Highly recommended to all noobs on Scan Tailor (likely Mac users like myself who've finally had a chance to try this software since the 0.9.9.1 build recently became an easier install) to watch the video twice before you start processing your ebooks: http://vimeo.com/12524529


This is the original thread:

All my raw images offloading from Canon A590IS are in JPEG format.

Scan Tailor produces its output files in TIFFs.

After sorting my photos into proper book order, should I export my images from JPEG-to-TIFFs for Scan Tailor? If I import the raw JPEGS into Scan Tailor, is there a reduction in quality (even if I specify the original raw dimensions)?

I'm assuming importing raw JPEGS produces the same quality as an exported full size TIFF. But I thought I'd ask seeing how it could be a crucial step in processing quality images.

I've tried exporting the raw JPEGS as TIFFs to discover the processing time increases, and this is understandable because the average TIFF export is 24 mb, where the JPEG raw files are about 3 mb.

My goal is the best resolutions for clean processing. For every ebook I make, I want a master copy--a high quality PDF, where I can choose to truncate it for mobile use if I choose.
Last edited by Anonymous on 07 Aug 2010, 15:08, edited 2 times in total.

Tulon
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Re: TIFF or JPEG?

Post by Tulon » 06 Aug 2010, 17:03

univurshul wrote:After sorting my photos into proper book order, should I export my images from JPEG-to-TIFFs for Scan Tailor? If I import the raw JPEGS into Scan Tailor, is there a reduction in quality (even if I specify the original raw dimensions)?
It makes no sense to convert JPEGs to TIFFs before processing them with Scan Tailor. Such a conversion would be lossless, meaning you are neigher gaining nor loosing quality. However, you do loose quality when your camera encodes images to JPEG. So, capturing in RAW rather than in JPEG format and converting that to TIFF might give you some extra quality.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

univurshul
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Re: TIFF or JPEG?

Post by univurshul » 06 Aug 2010, 17:12

Thanks, Tulon.

univurshul
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Re: TIFF or JPEG?

Post by univurshul » 06 Aug 2010, 18:07

Tulon wrote: It makes no sense to convert JPEGs to TIFFs before processing them with Scan Tailor. Such a conversion would be lossless, meaning you are neigher gaining nor loosing quality. However, you do loose quality when your camera encodes images to JPEG. So, capturing in RAW rather than in JPEG format and converting that to TIFF might give you some extra quality.

Well..I just found some interesting things about exporting to TIFFs, and it ties into the errors I've been experiencing with page splitting:

I've been working on processing a book. I had this idea to export my images out of iPhoto in TIFF format (for reasons that Scan Tailor produces TIFFs upon output, I wanted to keep a uniform file structure in the workflow, etc.). Last night when I did this, Scan Tailor split pages, and auto selected content throughout the book with high accuracy rates. (Keep in mind these are exported TIFFS).

After reading your post about how the exporting of JPEG-to-TIFF files makes no sense, I decided to run the same images in original JPEG format through Scan Tailor; nearly every image that once split perfectly in TIFF format now split incorrectly. EVERY image had issues, random and bizarre split lines, many images were edge-to-edge on the split.

My Camera is an A590IS, iPhoto offloads these images as JPEGS. This might be the only file option from what I can tell. This really means that TIFFs process better in Scan Tailor, even though JPEG-to-TIFF is not an improvement in quality, it's an improvement in automated processing.

Tulon
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Re: TIFF or JPEG?

Post by Tulon » 07 Aug 2010, 02:11

univurshul wrote:This really means that TIFFs process better in Scan Tailor, even though JPEG-to-TIFF is not an improvement in quality, it's an improvement in automated processing.
This means there is a bug somewhere. Could be specific to the OSX build, or might be caused by a new libjpeg being used.

I'd like to get one of those JPEG files where it fails.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

univurshul
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Re: TIFF or JPEG?

Post by univurshul » 07 Aug 2010, 02:19

here you go: http://dl.dropbox.com/u/7332578/Archive.zip

All of these JPEGS fail to split normally vs. their TIFF versions, and they also fail to select content.

Tulon
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Re: TIFF or JPEG?

Post by Tulon » 07 Aug 2010, 02:48

It worked more or less fine here. The small chapter name at the top, or whatever that was, was cut off on half of the pages, but that has nothing to do with JPEG vs TIFF. The only way I see converting to TIFF would make any difference is if you end up with a different DPI. Of course in that case you could just provide that different DPI when loading your JPEGs into Scan Tailor.
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

univurshul
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Re: TIFF or JPEG?

Post by univurshul » 07 Aug 2010, 04:02

Tulon wrote:It worked more or less fine here. The small chapter name at the top, or whatever that was, was cut off on half of the pages, but that has nothing to do with JPEG vs TIFF. The only way I see converting to TIFF would make any difference is if you end up with a different DPI. Of course in that case you could just provide that different DPI when loading your JPEGs into Scan Tailor.
Then it's a Mac problem. Because every page required manual adjusting when working with JPEGs.

univurshul
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Re: TIFF or JPEG?

Post by univurshul » 07 Aug 2010, 04:10

Tulon wrote:The only way I see converting to TIFF would make any difference is if you end up with a different DPI. Of course in that case you could just provide that different DPI when loading your JPEGs into Scan Tailor.

Both TIFF and JPEG are exactly the same DPI.

Tulon
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Re: TIFF or JPEG?

Post by Tulon » 07 Aug 2010, 04:18

univurshul wrote:Both TIFF and JPEG are exactly the same DPI.
Wait, the JPEGs you gave me didn't have any DPIs specified. Or maybe they had, but obviously wrong ones, so Scan Tailor rejected them and asked to enter them manually.
Did you enter those DPIs manually for TIFFs as well? Did you enter the same values for TIFFs and JPEGs?
Scan Tailor experimental doesn't output 96 DPI images. It's just what your software shows when DPI information is missing. Usually what you get is input DPI times the resolution enhancement factor.

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