I need to detect where objects (mostly people) are in relation to a wall. I can have a fixed position camera in the ceiling so I thought to get an image of the space with nothing in it. Then use the difference of that and the current camera image to get an image with just the things. Then I can do blob detection I think to get the positions (only need x).
Does this seem sound? I'm not very accomplished in OpenCV so am looking for some advice.
That would be one way of going about it, but not very robust as the video feed won't produce consistent precise images so the background will never be nicely subtracted out, and people walking through the scene will occlude light and could also possibly match parts of your background.
This process of removing the background from a video is simply dubbed "background subtraction" and there are built-in OpenCV methods for it.
OpenCV has tutorials on their site showing the basics, for both python and C++.
Related
I'm looking for a program that will enable me to quantity the difference between images in an image sequence over time.
We are hoping to use timelapse images to measure the activity of tadpoles by comparing how the images change over time. Tracking the movement of individuals isn’t necessary. The tadpoles are dark and the background of the aquarium is light, however the background isn’t uniform and some of the decor items like dark rocks and foliage make it so that all the tadpoles aren’t visible at all times.
Basically need a program that will allow me to quantity the differences/motion detected in an image sequence (i.e 209 images) and produce data that can be exported...
Any and all suggestions appreciated!!
Your question is rather vague and you don't supply any images or real indication of what you expect as results, so my answer will not be as thorough as it might otherwise be.
You don't mention any tools you are familiar with, but my recommendation would be Python and OpenCV. Alternatives are probably scikit-image, Python Wand.
In general, when trying to detect movement across a series of images, you would:
try and work out what the background is
look for movement by sutracting, or differencing, frames from the background
clean up the difference image
identify objects - maybe by shape or size or colour
maybe track objects
produce statistics
As regards working out the background, I did an example here by finding the median pixel across all images at each location in the images. There is also an OpenCV tutorial here.
As regards cleaning up images, you can probably remove noise in the background subtraction with a small median filter, say 3x3 or 5x5 depending on the resolution of your images.
As regards detecting tadpoles, you will probably want to use OpenCV findContours() and filter by size, or colour, or circularity. There are some fairly decent tutorials on PyImageSearch. There is also an ImageMagick "Connected Component" analysis to find a tennis player that I did here.
I'm creating motion detect app for ios. when camera on live any object passes the camera like person , animal. than i want detect motion feature. how's it possible?
I suggest you get familiar with the AVFoundation framework to understand how to get live video frames using the camera of an iOS device. A good starting point is Apple's famous sample AVCam, which should get you familiar with all the camera concepts.
As the next step, figure out how to do the movement detection. The simplest algorithm for that would be the background subtraction. The idea is to subtract two consecutive frames one from another. The areas without movement just cancel each other and become black, while the areas with movements show some nonzero values.
Here's an example of background subtraction in the OpenCV framework.
If in the end, you decide to use OpenCV (which is a classic Computer Vision framework which I definitely recommend), then you'll need to integrate OpenCV into your iOS app. You can see a short tutorial here.
I tried to show you some pointers which could get you going. The problem (how you presented it) is definitely not an easy one, so good luck!
I tried using cv2.createBackgroundSubtractorKNNto remove the background and highlight humans walking around from a GoPro footage, but the mask generated by the operation was unsubstantial. Here it is -> https://imgur.com/a/fDLzOTz. Footage: https://www.youtube.com/watch?v=sft1rSykoFo
After some investigation, I found that the camera has to be fixed in place for the method to work.
So how to get foreground (humans) from a non-fixed camera footage?
For this kind of problem you will need a semantic segmentation algorithm. It will recognise different objects in a scene and label every pixel with the corresponding recognised object.
There are several options: R-CNN, Mask R-CNN, Yolo, Unet.
If you want to build yourself, I strongly recommend watching Fast.ai videos. If you don't want to build yourself, you can use Google Vision API to get an annotated polyline of objects in an image.
I am working on an app in iOS that will occur an event if camera detects some changes in image or we can say motion in image. Here I am not asking about face recognition or a particular colored image motion, And I got all result for OpenCV when I searched, And I also found that we can achieve this by using gyroscope and accelerometer both , but how??
I am beginner in iOS.So my question is , Is there any framework or any easy way to detect motion or motion sensing by camera.And How to achieve?
For Example if I move my hand before camera then it will show some message or alert.
And plz give me some useful and easy to understand links about this.
Thanx
If all you want is some kind of crude motion detection, my open source GPUImage framework has a GPUImageMotionDetector within it.
This admittedly simple motion detector does frame-to-frame comparisons, based on a low-pass filter, and can identify the number of pixels that have changed between frames and the centroid of the changed area. It operates on live video and I know some people who've used it for motion activation of functions in their iOS applications.
Because it relies on pixel differences and not optical flow or feature matching, it can be prone to false positives and can't track discrete objects as they move in a frame. However, if all you need is basic motion sensing, this is pretty easy to drop into your application. Look at the FilterShowcase example to see how it works in practice.
I don't exactly understand what you mean here:
Here I am not asking about face recognition or a particular colored
image motion, because I got all result for OpenCV when I searched
But I would suggest to go for opencv as you can use opencv in IOS. Here is a good link which helps you to setup opencv in ios.
There are lot of opencv motion detection codes online and here is one among them, which you can make use of.
You need to convert the UIImage ( image type in IOS ) to cv::Mat or IplImage and pass it to the opencv algorithms. You can convert using this link or this.
As a part of my thesis work, I need to build a program for human tracking from video or image sequence like the KTH or IXMAS dataset with the assumptions:
Illumination remains unchanged
Only one person appear in the scene
The program need to perform in real-time
I have searched a lot but still can not find a good solution.
Please suggest me a good method or an existing program that is suitable.
Case 1 - If camera static
If the camera is static, it is really simple to track one person.
You can apply a method called background subtraction.
Here, for better results, you need a bare image from camera, with no persons in it. It is the background. ( It can also be done, even if you don't have this background image. But if you have it, better. I will tell at end what to do if no background image)
Now start capture from camera. Take first frame,convert both to grayscale, smooth both images to avoid noise.
Subtract background image from frame.
If the frame has no change wrt background image (ie no person), you get a black image ( Of course there will be some noise, we can remove it). If there is change, ie person walked into frame, you will get an image with person and background as black.
Now threshold the image for a suitable value.
Apply some erosion to remove small granular noise. Apply dilation after that.
Now find contours. Most probably there will be one contour,ie the person.
Find centroid or whatever you want for this person to track.
Now suppose you don't have a background image, you can find it using cvRunningAvg function. It finds running average of frames from your video which you use to track. But you can obviously understand, first method is better, if you get background image.
Here is the implementation of above method using cvRunningAvg.
Case 2 - Camera not static
Here background subtraction won't give good result, since you can't get a fixed background.
Then OpenCV come with a sample for people detection sample. Use it.
This is the file: peopledetect.cpp
I also recommend you to visit this SOF which deals with almost same problem: How can I detect and track people using OpenCV?
One possible solution is to use feature points tracking algorithm.
Look at this book:
Laganiere Robert - OpenCV 2 Computer Vision Application Programming Cookbook - 2011
p. 266
Full algorithm is already implemented in this book, using opencv.
The above method : a simple frame differencing followed by dilation and erosion would work, in case of a simple clean scene with just the motion of the person walking with absolutely no other motion or illumination changes. Also you are doing a detection every frame, as opposed to tracking. In this specific scenario, it might not be much more difficult to track either. Movement direction and speed : you can just run Lucas Kanade on the difference images.
At the core of it, what you need is a person detector followed by a tracker. Tracker can be either point based (Lucas Kanade or Horn and Schunck) or using Kalman filter or any of those kind of tracking for bounding boxes or blobs.
A lot of vision problems are ill-posed, some some amount of structure/constraints, helps to solve it considerably faster. Few questions to ask would be these :
Is the camera moving : No quite easy, Yes : Much harder, exactly what works depends on other conditions.
Is the scene constant except for the person
Is the person front facing / side-facing most of the time : Detect using viola jones or train one (adaboost with Haar or similar features) for side-facing face.
How spatially accurate do you need it to be, will a bounding box do it, or do you need a contour : Bounding box : just search (intelligently :)) in neighbourhood with SAD (sum of Abs Differences). Contour : Tougher, use contour based trackers.
Do you need the "tracklet" or only just the position of the person at each frame, temporal accuracy ?
What resolution are we speaking about here, since you need real time :
Is the scene sparse like the sequences or would it be cluttered ?
Is there any other motion in the sequence ?
Offline or Online ?
If you develop in .NET you can use the Aforge.NET framework.
http://www.aforgenet.com/
I was a regular visitor of the forums and I seem to remember there are plenty of people using it for tracking people.
I've also used the framework for other non-related purposes and can say I highly recommend it for its ease of use and powerful features.