I am checking a video, and would like to compare each frame with the previous one and return a black and white image consisting of all differences between the two frames.. like a "mask" of differences between the frames
Detect and visualize differences between two images with OpenCV Python
this link contains exactly what I would need, but it is in pythong, and I was not able to find the same method in .net. Its also my very first time working with emgu and I feel a bit lost.
I have 3 Mats, one is currentframe, oldframe and diffframe
any help on how this can be done is greatly appreciated!
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I'm currently learning OpenCV for a project I recently started in, and need to detect 3D boxes (imagine the big plastic boxes maybe 3ft x 2ft x 2ft) in an image. I've used the inRange method to create an image which just had the boxes I'd like to detect in it, but I'm not sure where to go from there. I'd like to get a 3D representation of these boxes back from OpenCV, but I can't figure out how. I've found quite a few tutorials explaining how to do this with just one object (which I have done successfully), but I don't know how I would make this work with multiple boxes in one image.
Thanks!
If you have established a method that works well with one object, you may just go with a divide-and-conquer approach: split your problem into several small ones by dividing your image with multiple boxes into an several images with one object.
Apply an Object Detector to your image. This Tutorial on Object Detection may help you. A quick search for object detection with OpenCV also gave this.
Determine the bounding boxes of the objects (min/max of the x and y-coordinates, maybe add some border margin)
Crop bounding boxes to get single object images
Apply your already working method to the set of single object images
In case of overlap, the cropped images may need some processing to isolate a "main" object. Whether 4. works is then dependent on how robust your method is to occlusions.
I stumbled over your question when looking for object detection. It's been quite a while since you asked, but since this is a public knowledge base a discussion on this topic might still be helpful for others.
I'm using OpenCV 2.4.2 VideoCapture class to grab frames from multiple videos and my aim is to compare the frames between videos to retrieve similar videos (visually similar).
I'm facing two issues.
The videos contain blank/black frames.
I can loop over each individual frame (while capturing the video) and check the pixels etc. to detect these frames. Is there a faster and more efficient way to somehow do this? I have more than 1k videos and each video has around 5k-20k frames [I'm capturing 1 frame per second]. I'm coding in C++.
Comparing two huge matrices to check how "similar" they are.
I eventually compute a huge matrix for each video where the rows correspond to the number of the frames, and the cols correspond to the dimensionality of the descriptor being computed on each frame. If I need to compare two videos for similarity, the simplest thing I found was to compute Euclidean matrix. But again, horribly inefficient if I scale up to 1000s of videos.
Any advice and suggestion will be appreciated.
Thanks,
Concerning the first problem, I think cv::countNonZero is the most suitable method, it works very fast as well. cv::countNonZero returns the number of non-zero elements in input single-channel array.
heylo!
I have a bunch of old video files converted from old vhs tapes. The problem is, since those tapes were really old, the videos are jumpy (sometimes the bottom of the frame is in the middle of the screen followed by the top of the next frame)
My goal is to write something in opencv to automatically remove the frames where the image is not lined up properly.
My idea is to detect the difference between the previous frame and the next frame. If the video were smooth, the difference would be minimal. If the frame is jumpy then the difference would be noticeable.
My question: how would opencv calculate this difference between two frames?
Thx!!!!
I hope you know how to grab frames from video. If not, check here. Fortunately, it also finds similarity between two videos.
What you will learn in this tutorial:
How to open and read video streams
Two ways for checking image similarity: PSNR and SSIM
I think you can just make small adaptations to it as per your requirements. This tutorial has all enough information about it.
You can also check this SOF : Simple and fast method to compare images for similarity
I'll first tell you the problem and then I'll tell you my solution.
Problem: I have a blank white PNG image approximately 900x900 pixels. I want to copy circles 30x30 pixels in size, which are essentially circles with a different colour. There are 8 different circles, and placed on the image depending on data values which I've created elsewhere.
Solution: I've used ImageMagicK, it's suppose to be good for general purpose image editing etc. I created a blank image
Image.outimage("900x900","white");
I upload all other small 30x30 pixel images with 'read' function.
I upload the data and extract vales.
I place the small 'circle' images on the blank one using the composite command.
outimage.composite("some file.png",pixelx,pixely,InCompositeOp);
This all works fine and the images come up the way I want them too.
However its painfully SLOW. It takes 20 seconds to do one image, and I have 1000 of them. Surely there must be a better way to do this. I've seen other researchers simulate images way more complex and way faster. It's quite possible I took the wrong approach. Maybe I sould be 'drawing' circles instead of 'pasting' them or something. I'm quite baffled. Any input is appreciated.
I suspect that you just need some library that is capable of drawing circles on bitmap and saving that bitmap as png.
For example my Graphin library: http://code.google.com/p/graphin/
Or some such. With Graphin you can also draw one PNG on surface of another as in your case.
You did not give any information about the platform you are using (only "C++"), so if you are looking for a platform independent solution, the CImg library might be worth a try.
http://cimg.sourceforge.net/
By the way, did you try drawing the circles using the ImageMagick C++ API Magick++ instead of "composing" them? I cannot believe that it is that slow.
I am working on a project to stitch together around 400 high resolution aerial images around 36000x2600 to create a map. I am currently using OpenCV and so far I have obtained the match points between the images. Now I am at a lost in figuring out how to get the matrix transformation of the images so I can begin the stitching process. I have absolutely no background in working with images nor graphics so this is a first time for me. Can I get some advice on how I would approach this?
The images that I received also came with a data sheet showing longitude, latitude, airplane wing angle, altitude, etc. of each image. I am unsure how accurate these data are, but I am wondering if I can use these information to perform the proper matrix transformation that I need.
Thanks
Do you want to understand the math behind the process or just have an superficial idea of whats going on and just use it?
The regular term for "image snitching" is image alignment. Feed google with it and you'll find tons of sources.
For example, here.
Best regards,
zhengtonic
In recent opencv 2.3 release...they implemented a whole process of image stitching. Maybe it is worth looking at.