Interactive pixel information of an image

There a couple of different ways to go about this. You can monkey-patch ax.format_coord, similar to this official example. I’m going to use a slightly more “pythonic” approach here that doesn’t rely on global variables. (Note that I’m assuming no extent kwarg was specified, similar to the matplotlib example. To be fully general, you need … Read more

Python – Find dominant/most common color in an image

Here’s code making use of Pillow and Scipy’s cluster package. For simplicity I’ve hardcoded the filename as “image.jpg”. Resizing the image is for speed: if you don’t mind the wait, comment out the resize call. When run on this sample image, it usually says the dominant colour is #d8c865, which corresponds roughly to the bright … Read more

What is the most efficient way to display decoded video frames in Qt?

Thanks for the answers, but I finally revisited this problem and came up with a rather simple solution that gives good performance. It involves deriving from QGLWidget and overriding the paintEvent() function. Inside the paintEvent() function, you can call QPainter::drawImage(…) and it will perform the scaling to a specified rectangle for you using hardware if … Read more

Remove spurious small islands of noise in an image – Python OpenCV

A lot of your questions stem from the fact that you’re not sure how morphological image processing works, but we can put your doubts to rest. You can interpret the structuring element as the “base shape” to compare to. 1 in the structuring element corresponds to a pixel that you want to look at in … Read more

module’ object has no attribute ‘drawMatches’ opencv python

I am late to the party as well, but I installed OpenCV 2.4.9 for Mac OS X, and the drawMatches function doesn’t exist in my distribution. I’ve also tried the second approach with find_obj and that didn’t work for me either. With that, I decided to write my own implementation of it that mimics drawMatches … Read more