Tagged Questions

OpenCV (Open Source Computer Vision) is a cross-platform library of programming functions for real time computer vision. It was officially launched by Intel in 1999 and is now supported by Willow Garage. Uses include: Human-Computer Interaction; Object Identification, Segmentation and ...

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Drawing a Line On A White Image in OpenCV

I'm attempting to draw a graph on a blank image, using the cvLine method to go from point to point. Holder[] is an array of floaters. I have checked the array by printing out values, so it is not ...
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How to access the nearest neighbours found by a cv::flann knnsearch?

Or is it even possible with flann ? Im not the most experienced coder, I also might just be overlooking something really basic (C++,OpenCV 2.4.3.) The problem : I have two pointclouds and want to ...
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10 views

How multiscale detection loop works in OpenCV's HOG detection?

In the Dalal and Triggs paper about HOG, it seems like the multi-scale detection works by scanning through the image pyramid. But I can't find which part of modules/objdetect/src/hog.cpp that do the ...
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1answer
47 views

OpenCV Buffer Overflow

I've got myself in a pickle on this project I'm working on. My main objective is to stitch two webcam feeds together and do object detection on them - bounding boxes, etc...the standard stuff. I ...
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2answers
318 views

why does cvGetCaptureProperty(video,CV_CAP_PROP_POS_FRAMES) returns 0 on Windows 7 64bit machine?

I am running a code to extract optical flow on a movie and I want to run it on all the frames of the movie. However, when i use number_of_frames = (int) cvGetCaptureProperty( input_video, ...
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13 views

How to use camera on packed Tkinter canvas (opencv)

could someone explain me why after modyfication of commented out code there is no camera view more? I get error message " self.a = Image.fromarray(self.capture)#PIL 1.6# AttributeError: class ...
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14 views

focal length fx and fy , do they change for a camera capable of zooming? [closed]

Hii I am using a logitech PTZ camera . i am trying to find the intrinsic camera matrix from opencv . Do the fx and fy values change when calibrated differently ?? Or are they constant ? i am using ...
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24 views

OpenCV contourArea returns NaN value

I'm using the contourArea as a criteria to select big shapes in my image, but it appears that it often returns me a NaN value. Here's the code: cv::Mat gridMat = cv::Mat::zeros(g.getDim().x+2, ...
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15 views

Mat Single channel Element Access

Using three channel Mat we can access element like Mat draw(480, 480, CV_8UC3); Vec3b pix(255,0,0); draw.at<Vec3b>(i,j)=pix; But in the case of single channel Mat like Mat draw(480, 480, ...
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1answer
23 views

train data must be floating-point matrix in function cvCheckTrainData runtime error

Hi my training data contains numbers of type long double(like 1.6448e-43, -6.08498e-36). which OpenCV datatype should i use in the following code: Mat training_data = Mat(NUMBER_OF_TRAINING_SAMPLES, ...
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1answer
778 views

How to verify the correctness of calibration of a webcam

i am totaly new to camera calibration techniques...i am using OpenCV chessboard technique...i am using a webcam from Quantum...here are my observations and steps.. i have kept each chess square side ...
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2answers
378 views

How To detect Image Orientation & skew In ObjectiveC

I want to detect Image Orientation & skewing and rotate the image to be ready For scanning using OCR. how to do in ObjectiveC
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28 views

How to apply perspective transofrmation to ellipse?

Having transformation in a matrix, which can be applied to points, how to apply the same transformation to ellipse? Most general parameter ellipse function accepts is RotatedRect, which is not so ...
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1answer
57 views

Making a video with opencv, getting only 1 frame

I've been trying to add a video making module to my program using opencv, but try as I might I can't get the video to show more than 1 frame. I got this example code while searching for answers ...
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16 views

OpenCV 2.4.3 displays video as grey window

I have a desktop and laptop running OpenCV 2.4.3 on x64 architectures one on Win 7 and the other on Win 8 both running VS 2012 x64. I've compiled OpenCV on both computers. The desktop running Win 7 ...

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