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2015-02-17 18:24:03 -0500 asked a question How to find contours only in black colour?

I try to remove noises from an image. I have some black group of pixels in the image. I use cv::findContours and cv::boundingRect. And I fill small rectangles (small rectangles are noises in the image) with white colour. But this method also find me white contours (for example middle of black circle). How to find countours for black pixels? Is there any easy solution?

2015-02-17 05:05:22 -0500 asked a question Program to recognize music notation

I wrote program to recognize music notation (exactly tabulature). In the main there are digits on the lines. After preprocessing (global binarization) I remove lines. I'd like to ask about preprocessing. My program works fine where lines and digits have the same color. But lines are often lighter than digits. When I use binarization with small threshold lines disapear when I use binarization with bigger threshold there are too many noises and digits are thick.

What kind of binarization (in OpenCV) can you recommend? What to do? Is there any solution for this problem?

I'll add some example.

My preprocessing looks like that:

1) Reading image in gray colors:

enter image description here

2) GLobal binarization:

cv::threshold (for example 127)

enter image description here

Characters are not beautiful... :( But main problem is that lines disappeared.

3) cv::threshold (230)

I can see lines but charackters are thick and ugly. For example 'a' character sometimes does not have empty space in the middle and so on. And there are a lot of noises. :(

enter image description here

And there is one more problem... I have to set threshold value for every file....

Do you have any suggestion for preprocesssing???

I'd like to have "nice" lines and characters...

(I don't ask about code, just some suggestions and advices)

2015-01-23 16:59:03 -0500 commented question OCR in openCv - how to locate letters

Thanks a lot.

2015-01-23 08:41:12 -0500 commented question OCR in openCv - how to locate letters

No, I don't want you to solve it for me. I asked only for name of class/function. Name of method. Not pasting code. I've found the most popular (the most linked) tutorial by Damiles. It hasn't got this step. I'm beginner I ask only what class/function I should learn. Is it too much for this forum?

2015-01-23 07:58:15 -0500 asked a question OCR in openCv - how to locate letters

I want to write some kind of OCR in openCV (C++). It's not an OCR for normally text. I have letters in random places on the white background (with small noises).

Before recognizing letters I'd like to find them.

How to do that the best? I'd like to get them as matched rectangle area or vectors of Points with found letter.

2014-10-05 09:46:45 -0500 asked a question Line detection as only one line

I have scanned papers with some quite straight lines. I'd like to get every line as a mathematical function. In openCV there is HoughLinesP that detect lines but it shows upper edge of my line and bottom edge of my line. The second problem is that there is usually few lines very close to themselves (because lines are not perfect). I need method that show me only one line the most closest to my scanned line.

What should I use?

2014-10-05 09:13:01 -0500 asked a question OpenCV 3.0 missing lib files after downloading

Hi,

Does anyone use OpenCV 3.0 with visual studio? I've downloaded the latest version (3.0) and I cannot find necessary lib files: opencv_calib3d300d.lib opencv_core300d.lib opencv_features2d300d.lib ... etc

I really need 3.0 version...

Please help me...

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2014-10-01 17:16:03 -0500 asked a question Noise removal from scanned documents

Hi,

I'm just beginning with OpenCV and image processing. I need to write program that processing scanned documents (they are sometimes old) and I need to recognize some objects. I'd like to ask you for help where to search and what functions should I use for beginning processing. I think about removal every noise. My scanned documents are only in gray colors (written in black or similar on bright background).

1) What function should I use to remove noises from this kind of scanned documents? I've found fastNlMeansDenoising. Is it ok for this puropse?

2) Some documents can have ... (I don't know how it is in English language). I mean that we can see undesirable effect that there is 'shadow' of other side of the paper. What is the best method to remove this effect? "treeshold" is a good idea?