I’ll never get tired of telling people that the C++ OpenCV interface for Windows has the wierdest bugs. Write a small test using the C interface to check if it works or not (cvLoadImage(), etc). Update: now that you know that the C interface works properly, you can either go to the mailing list and … Read more
As you want step by step procedure, So I would start with creating a SampleOpenCV project from scratch, and would also suggest to do the following steps in a new project, Once it starts working you may try to migrate the changes to your main project. Download OpenCV package for android from Opencv.org [ Direct … Read more
I tried the following and it worked: Change in FindCUDA.cmake the nppi library to the several splitted ones. This has to be done in 3 places. Remember this change is just to make it work with CUDA 9.0, I am not doing checks for version or anything, which should be done if you plan to … Read more
cv::Mat is the new type introduce in OpenCV2.X while the IplImage* is the “legacy” image structure. Although, cv::Mat does support the usage of IplImage in the constructor parameters, the default library does not provide function for the other way. You will need to extract the image header information manually. (Do remember that you need to … Read more
If it’s giving you errors with gtk, try qt. sudo apt-get install libqt4-dev cmake -D WITH_QT=ON .. make sudo make install If this doesn’t work, there’s an easy way out. sudo apt-get install libopencv-* This will download all the required dependencies(although it seems that you have all the required libraries installed, but still you could … Read more
AFAIK, you have to convert it to grayscale and then threshold it to binary. 1. Read the image as a grayscale image If you’re reading the RGB image from disk, then you can directly read it as a grayscale image, like this: // C IplImage* im_gray = cvLoadImage(“image.jpg”,CV_LOAD_IMAGE_GRAYSCALE); // C++ (OpenCV 2.0) Mat im_gray = … Read more
How to calculate distance given an object of known size You need to know one of 2 things up front Focal-length (in mm and pixels per mm) Physical size of the image sensor (to calculate pixels per mm) I’m going to use focal-length since I don’t want to google for the sensor datasheet. Calibrate the … Read more
The Function adds gaussian , salt-pepper , poisson and speckle noise in an image Parameters ———- image : ndarray Input image data. Will be converted to float. mode : str One of the following strings, selecting the type of noise to add: ‘gauss’ Gaussian-distributed additive noise. ‘poisson’ Poisson-distributed noise generated from the data. ‘s&p’ Replaces … Read more
You can use ord() function in Python for that. For example, if you want to trigger ‘a’ key press, do as follows : if cv2.waitKey(33) == ord(‘a’): print “pressed a” See a sample code here: Drawing Histogram UPDATE : To find the key value for any key is to print the key value using a … Read more
*edit – updated to work with images that have an alpha channel. This worked for me: Make a mask with all black (all masked) Fill a polygon with white in the shape of your ROI combine the mask and your image to get the ROI with black everywhere else You probably just want to keep … Read more