OpenCV (Open Source Computer Vision) is a cross-platform library of programming functions for real time computer vision.

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regionprops vs. findContours doesn't find the same contours

Is there a way to get the same results for cDist=regionprops(bwImg, 'Area'); and openCV's findContours? Here is what I have tried so far: ...
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37 views

Isolate the non blurred part of foucsed image

I have an image taken by a mobile phone camera with focus on a part of it let say a face or whatever. I want to know -approximately- where is the focused area. For example, a bounding box around the ...
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13 views

Hue out of range

I don't why.. but for some reason is my histogram showing that the max hue value of my image is around 339498 which doesn't make sense for me.. I am trying to create a mask, that recognizes the ...
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1answer
38 views

How to calculate the luminance of an image?

Is there any method for calculating luminance of an image? As from wiki got to know Luminance is an amount of energy perceived by the observer and LUX is different from brightness. But still is ...
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32 views

snr calculation of frame

I have to calculate SNR of an image. I have camera through which continuous images are getting generated, my requirement is to calculate the SNR in db for each image. I have seen lot of the examples ...
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15 views

Coherence of specific area of an image

I have to detect an object in an image. The manner that I am using gives me a number of possible areas of the image that may contain the object. I want to check which is the most coherence area of ...
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33 views

Primitive Feature Detection

I am trying to check whether this black circle is exist or not on my images. My current approach is like that; Hough Circle detection Crop the outer roi Adaptive threshold count zero ...
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1answer
40 views

Skew detection and correction using Fourier transform

I was trying to implement skew correction method for scanned documents using the method described in this paper. The algorithm steps: 1- Threshold the image . 2- Find the fourier transform. 3- ...
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87 views

Detect text regions within scanned documents

I'm working on text detection task from scanned documents to detect text regions only and separate them from images, graph, etc. Here is my idea : First i'm using OpenCV wrapper for C# (Emgu) on ...
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2answers
49 views

Removing the 'red' artifact from my JPEG

I have a JPEG that originally came from a IP Camera. I have converted the JPEG to a bytes and have uploaded it to my server. Upon receiving it on my server I save it to disk. When I view the image it ...
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61 views

Efficient Hessian-Laplace blob detector implementation

As it is mentioned in a paper for SURF, it is possible to approximate hessian determinant using integral images. If I want to implement Hessian-Laplace detector, is it feasible to also approximate ...
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21 views

contour matching

Im am trying to extract contours from an image and match them with a list of contours I already have. The contours in the image are surrounded by a large black/dark rectangle. Here are the steps I ...
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1answer
66 views

How to analyse Phase spectrum of 2D signals?

I am beginner in image processing. When I applied Fourier transform on two images say Lena and Cameraman etc., I obtained magnitude and phase spectrum for each one. I want to concentrate on phase ...
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96 views

Circle detection opencv

I Would like an explanation of the parameters for opencv's HoughCircles function. I'm new to image processing in general and I have recently started using opencv. ...
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52 views

DFT and Inverse DFT in Image Processing

I have implemented DFT from this link. 1) Tried taking dft for the three Channels(R, G and B) and reconstructed the original image by taking inverse dft for all three channels and merged them ...
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37 views

Non-maxima suppression of gradient image

I'm new to image processing, However I was trying to learn how to detect edges using Sobel filter I had obtained the image gradient in both X and Y directions successfully using Emgu built in ...
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30 views

How to compute Gradient of an image with kernel in python

Using python numpy or scipy I am trying to perform cross-correlation on each pixel of an image using a 3 dimensional kernel. I am more interested in looping into each pixel and applying the kernel ...
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11 views

Measuring contrast of a jpeg

I am knew to image processing. I am using Emgu C# I want to somehow measure the contrast of an image. It would be enough for my purposes to say ImageA has more contrast than ImageB. I have spent ...
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1answer
61 views

How to remove text region in a document image? or extract image from a document image

Given a document image (i.e. newspaper), how to extract photos in it or remove text region? I think traditional OCR methods may not be suitable here, as I don't need to recognize the text, and OCR is ...
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25 views

How do I deal with occlusion, warping, or perspective distortion for object detection

I am using SIFT features for detecting logos in clothes. SIFT is quite powerful, as it is scale invariant, but how do I deal with the problem of occlusion and warping? More specifically, the logos in ...
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25 views

Creating a texture image from existing image

I have some unusual question. I have searched online and couldn't find something similar to what I want to achieve. I have an image, and I want to create a new image from it (in the same size), so ...
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27 views

what are moments?

Hello all I'm using opencv after using findcontours I apply moments here is the vague wiki definition - http://en.wikipedia.org/wiki/Image_moment Can someone please explain in simpler words - ...
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4answers
75 views

Is this image good enough for OCR?

Hello I'm trying to ocr on a special image. I've done adaptive threshold , polartocartesian transformation. this is my original image this is adaptive threshold this is polartocartesian ...
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25 views

Gap Filling Contours / Lines

I have the following image: and I would like to fill in its contours (i.e. I would like to gap fill the lines in this image). I have tried a morphological closing, but using a rectangular kernel ...
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1answer
24 views

How to choose suitable segmentation process for image processing

Hello I'm new on image processing. I know there are a lot of threshold and region growing algorithms to use. But I would like to know what is the trick for choosing suitable method for an image ? ...
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2answers
178 views

How to remove the noise without destroying the main edge?

I am working on a project. I want to segment a logo from a car and the picture's size is 3648*2432. The logo is selected by the red rectangle. I extracted this area and turn into gray level. The ...
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1answer
123 views

Is it possible to hack camera calibration without having access to the camera?

Many times we have a stream of video to process without access to camera. Having access to camera matrix would be beneficial for various processing techniques. Is it possible to hack camera ...
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47 views

opencv4Android,How to draw good matches?

I am doing a project on panoramic stitching of Images using openCV4Ansroid and I want to use features2d to draw good matches ...
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1answer
92 views

Feature Detection on a Circular Metal Surface for Character Recognition

Hello I'm trying to recognize characters on the circular metal surface. Without any preprocessing I could match cropped features with original image. I've actually cropped 2 characters together to ...
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1answer
227 views

OpenCV Motion Analysis: Optical Flow vs Motion History

OpenCV Motion Analysis Documentation lists multiple techniques for motion tracking: Sparse Optical Flow | calcOpticalFlowPyrLK, Dense Optical Flow | calcOpticalFlowFarneback, and Motion History ...
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53 views

How to choose extrinsic parameters when projecting 3d points to 2d points?

I want to use voxel carving to realize the reconstruction of a target. Three cameras placed at orthogonal places as follows: One important step is that I have to back project 3d points to 2d points ...
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1answer
195 views

How to detect the exception by SVM with openCV

I have implemented SVM by openCV. However, I have a problem about SVM with openCV. For example, I have six categories, but I just use "five" of them to train my SVM. When testing, I want my system ...
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112 views

Why Normalized Cross Correlation Score of different templates is high?

I am using OpenCv's built in template matching function to search for an object in image. I am using Normalized Cross Correlation Method.The function is returning a value which I think indication of ...
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1answer
62 views

Shape recognition, hough transform

I'm trying to match a picture saying "this is ducks, this is towers" by giving votes from the hough transform of a picture. I've found this article ...
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1answer
29 views

Does accurate translation estimation using a camera matrix mean the orientation estimation will also be accurate?

Pose Estimation of single camera and planar pattern: If I have an appropriate camera matrix with intrinsic parameters that allows me to calculate translation of the camera relative to a chessboard, ...
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1answer
275 views

Detecting text lines in image by means of Hough Transform

In my Android App,I have to detect text lines in images.I want to use Hough Transform to detect lines.You can see an image below: I got edges in image by ...
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93 views

Image processing: Importance of phase

I was doing some experiment on image processing. I wanted to explore the importance of phase and Magnitude. I followed the following approach: Take 2 image of same dimension. Apply Fourier ...
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44 views

Best segmentation method

This is part of my samples ...
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1answer
114 views

Skeleton from distance map

Can anyone give some tips how to obtain Skeleton from distance map? I already managed to obtain skeleton using erased method (e.g. zhang suen) but it's time consuming because it's an iterative method ...
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2answers
441 views

Finding local brightness maximas with OpenCV

I want to find points (of a processed image) that are the brightest in their local region. Basically, I want all of the points whose 8 neighbors are all smaller but I want to have brighter maxima ...
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1answer
66 views

Is a change in colorspace needed when comparing colors only evaluated by the computer?

I am confused about the need to change color space for color comparison. I have read about delta E, the Lab format, and I do understand that comparisons in the RGB color space will not seem ...
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134 views

Why is LBP generaly faster than HAAR?

I am digging into Haar like and LBP features. More precisely its implementation in OpenCV. Every article or forum entry I found states, that LBP is faster than Haar. My local tests also confirm this ...
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2answers
228 views

Template matching or object recognition?

Problem: I have a photo of an object (a manufactured part like the attached photo below), using my Andoird phone camera I want to verify if the object in camera preview matches to the template or not. ...
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48 views

Problem in openCV casade classifier

I am trying to train cascade classifier using "opencv_traincascade" utility. I'm having 100 positive images and 500 negative images. I have created .vec file using following command: ...
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25 views

High triangulation error

I have implemented a 2D->3D point triangulation method, which uses 2 poses P1 and P2 and 2 points back-projected to z=1 point1 and point2 to recover depth: ...
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60 views

State of the art post processing techniques for segmented images

I've been working on grabcut-based approaches to human segmentation in images. I've combined colour, motion and face detection cues to provide some seeds and perform a grabcut. While the results have ...
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113 views

Visual regression test - Extract elements of GUI-Screenshot - MSER OpenCV

For a visual regression test I need to compare screenshots of webpages (different release-versions). I started with pixel by pixel compare. Actually I split the screenshot in different parts (maybe ...
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1answer
132 views

Using ROC curves for comparing the performance of SIFT and SURF

I want to compare the performance of SIFT and SURF against some standard image set. After a bit of research, I found that ROC curves are one of the best ways to do this task. In order to plot ROC ...
2
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1answer
557 views

Zernike Moments' implementation in OpenCV

The reason why Hu moments were implemented in OpenCV and why Zernike moments were not implemented is looking like their performance similar as stated in this paper. As stated in the paper Zernike ...
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287 views

MPEG-7 descriptors' implementation in OpenCV

I'm looking for implementation of MPEG-7 descriptors which are compatible with OpenCV's recent versions and containing "region-based shape descriptor ART(Angular Radial Transformation)". I ...