Category: Computer Vision

There are times when you need to find straight lines on an image. This can be done using OpenCV’s built in implementation of Hough Line Transform.

It is very interesting to see how Hough Line Transform actually works. Assume (as displayed in figure below) we have a line segment AB. In the Cartesian coordinate system, the line can be represented as y = mx + c. Now if we want to represent the same line in polar coordinate system, it can be represented as y=(−cosθ/sinθ)x+(r * sinθ)

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At times when working in OpenCV with Videos, since there is no easy way to tell how long the video is going to be, or if you are planning to post the video on Social media like Instagram that do not show video progress bar, you may want to embed progress bar on the video itself. There is no build in feature on OpenCV, so we shall write a function that will achieve the same.

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OpenCV provides a lot of useful functions to work with images and video files. One such operation is saving video using OpenCV. However, saving video with OpenCV, although is a straightforward operation, but at times it becomes very time consuming to debug because of some silly mistakes. Any time there is any issue, the frames do not get added to video file, and the video thus generated does not work. For example if the extension of video file saved does not match the encoding that we are using, the video file does not get written. Similarly, if there is issue with fps or frame size, the video file does not get written to and hence does not work.

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OpenCV is very powerful opensource image processing library. It can be used to carry out various operations on images. Today we are going to explore how we can use OpenCV to find and highlight the differences between 2 images.

This is a very powerful technique and it can have many uses including, security surveillance (finding difference between subsequent frames of security camera), hardware machine monitoring and maintenance forecasting, software testing (taking snapshots of pages and comparing them for change overtime or after new release) etc. Applicability of it is only limited by your imagination.

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