<p>I'm working on a document storage project and i found a problem.</p>

<p>After converting/compressing a scanned document to black &amp; white sometimes, some areas of the document are unreadable because shadows are transformed to black chunks.</p>

<p>Is it possible to find out when this black chunks are present on the images?</p>

<p>the intuiton of this validation is to mark the file as unreadable to manual analisys.</p>

CC BY-SA 3.0
2016-08-05T18:12:32.563Z
I'm not sure, but if you scan a document multiple times with slightly different tiny offsets, resulting in slightly different scans of the same document, you should be able to use that information to do Monte Carlo style sampling and get a better result of your scans.

If you don't get any good answers here, another venue that is likely to be able to help you is the digital signal processing stack exchange: http://dsp.stackexchange.com/
Alan Wolfe
CC BY-SA 3.0
2016-08-05T20:04:50.620Z
Could you add more detail about the characteristics of the documents being scanned? At present it's difficult to judge whether this is on topic. For example, if the documents have arbitrary sized fonts and images, the task will be different than if the documents have a single small font size with no images.
trichoplax is on Codidact now
CC BY-SA 3.0
2016-08-07T12:06:21.213Z
Can you even add an example of such artifact so we can have a look at it?
Julien Guertault
CC BY-SA 3.0
2016-08-08T07:48:40.930Z
The problem is that i cannot access the physical document, I only have access to the output of the scan. 
Most of the documents are text or ID Card.
I cannot had an example because all of the documents that I have access are confidencial.
Daniel Diogo
CC BY-SA 3.0
2016-08-15T03:18:59.837Z
When you say "black and white" do you literally mean 1-bit per pixel images where each pixel is either fully black or fully white? Or do you actually mean grayscale (where there are shades between fully black and fully white)? What type of compression is used?
user1118321
CC BY-SA 3.0
2016-09-15T09:10:03.727Z
I can't find a really good solution but the closer I could get was to use Aforge library to help me detect blobs, not really a good solution but works. 

For the project where I work we change the operation so now people decide if the document has quality or not. 

For compressing I divide TIFF in pages then convert to JPEG reduce the quality and then add it to a pdf file, sometimes achieving around 80% less space occupied.
Daniel Diogo
<algorithm><transformations><optimisation><blur>
detect blurred zones after conversion to black & white
Daniel Diogo
# detect blurred zones after conversion to black & white

(Asked by: username_0 on 2016-08-05)

I'm working on a document storage project and i found a problem.

After converting/compressing a scanned document to black & white sometimes, some areas of the document are unreadable because shadows are transformed to black chunks.

Is it possible to find out when this black chunks are present on the images?

the intuiton of this validation is to mark the file as unreadable to manual analisys.

**Tags:** algorithm, transformations, optimisation, blur

> **Comments:**
> **username_1**: I'm not sure, but if you scan a document multiple times with slightly different tiny offsets, resulting in slightly different scans of the same document, you should be able to use that information to do Monte Carlo style sampling and get a better result of your scans.  If you don't get any good answers here, another venue that is likely to be able to help you is the digital signal processing stack exchange: http://dsp.stackexchange.com/  
> **username_2**: Could you add more detail about the characteristics of the documents being scanned? At present it's difficult to judge whether this is on topic. For example, if the documents have arbitrary sized fonts and images, the task will be different than if the documents have a single small font size with no images.  
> **username_3**: Can you even add an example of such artifact so we can have a look at it?  
> **username_0**: The problem is that i cannot access the physical document, I only have access to the output of the scan.  Most of the documents are text or ID Card. I cannot had an example because all of the documents that I have access are confidencial.  
> **username_4**: When you say "black and white" do you literally mean 1-bit per pixel images where each pixel is either fully black or fully white? Or do you actually mean grayscale (where there are shades between fully black and fully white)? What type of compression is used?  
> **username_0**: I can't find a really good solution but the closer I could get was to use Aforge library to help me detect blobs, not really a good solution but works.   For the project where I work we change the operation so now people decide if the document has quality or not.   For compressing I divide TIFF in pages then convert to JPEG reduce the quality and then add it to a pdf file, sometimes achieving around 80% less space occupied.  

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