How to remove non uniform background from image [closed]

Question

Closed. This question needs to be more focused. It is not currently accepting answers.

Want to improve this question? Guide the asker to update the question so it focuses on a single, specific problem. Narrowing the question will help others answer the question concisely. You may edit the question if you feel you can improve it yourself. If edited, the question will be reviewed and might be reopened.

Closed 2 months ago.

Improve this question

Receipt clip contains structured background:

Tried to remove it using textcleaner ImageMagic wrapper script from Remove receipt image border using ImageMagick answer. Used code from answer How to use imagemagick.net in .net ? :

var proc = new Process
{
    StartInfo = new ProcessStartInfo
    {
        FileName = "textcleaner.sh",
        Arguments = "-f 20 -o 10 -e normalize krooningtaust.jpg result.jpg",
        UseShellExecute = true,
        RedirectStandardError = true,
        CreateNoWindow = true
    }
};

proc.Start();
string error = proc.StandardError.ReadToEnd();
proc.WaitForExit();

In result background still exists and tesseract Single Block Page segmentation mode does not recognize text:

How to remove background fully using C# .NET 9 or force Tesseract Single Block PSM mode do recognize text from it?

It looks like text is converted to blue color. How to remove all non- blue pixels or force Tesseract to use only blue for OCR ?

this issue is now spread across four questions: (1) stackoverflow.com/questions/79766914/… (2) stackoverflow.com/questions/79765653/… (3) stackoverflow.com/questions/79760516/… (4) stackoverflow.com/questions/79758362/… — Christoph Rackwitz
– Christoph Rackwitz, Commented Sep 17 at 8:03
I deleted fourth question you referenced. Questions 1-3 are different. Questons 2-3 have good answers. — Andrus
– Andrus, Commented Sep 17 at 9:29

Mark Setchell · Accepted Answer · 2025-09-10 08:42:08Z

There are probably better ways to approach this problem but I don't have the benefit of time today, so I'll just answer your question about removing all non-blue pixels, using ImageMagick.

A suitable command would be:

magick receipt.jpg -fill white -fuzz 25% +opaque "rgb(18,90,198)" result.jpg

That says... "take my image, and fill with white all pixels that are not within 25% of rgb(18,90,198) and save as 'result.jpg'"

You may want to quantise to convert to black and white, threshold and save as lossless PNG as well:

magick receipt.jpg -fill white -fuzz 25% +opaque "rgb(18,90,198)" -colorspace gray -threshold 50% result.png

Further idea:

You might consider taking the image resulting from the above command and running a median filter to get rid of outlier pixels and then get the "cropbox" of the result:

magick result.png -statistic median 5 -format "%@" info:
739x1974+420+220

That tells you where to crop the image to exclude borders. You can then apply that to your original image:

magick receipt.jpg -crop 739x1974+420+220 cropped.png

In case you want to understand the "fuzz" distance it is expressed as a percentage of the distance from the black apex to the white apex in an RGB color cube. So, in a unit cube (one with sides of length 1.0), the black to white distance would be sqrt(3) and distances between colours (i.e. fuzz) would be expressed as a percentage of that.

Great. How to merge textcleaner and your script so that only pure imagemagic can used? According to doc textcleaner does convert $ $infile -colorspace gray -type grayscale -contrast-stretch 0 $ $ -clone 0 -colorspace gray -negate -lat ${filtersize}x${filtersize}+${offset}% -contrast-stretch 0 $ \ -compose copy_opacity -composite -fill "$bgcolor" -opaque none +matte \ -deskew 40% -sharpen 0x1 \ $outfile
If you remove $outfile from the end of textcleaner command, you'll be in exactly the same position as my command is after magick receipt.jpg so you can then just continue with my -fill white -fuzz ... -opaque ... $outfile
How to convert this to c# code using imagemagick nuget package or other method?. Tried to use OpenCV but background is not removed as descibed in stackoverflow.com/questions/79765653/…
Conversion parameters in queston produced empty image. Modified parameters worked as posted in stackoverflow.com/questions/79766914/… After conversion text quality is poor. In original image text quality is better. How to make image quality better?

Collectives™ on Stack Overflow

How to remove non uniform background from image [closed]

1 Answer 1

4 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Linked

Related