I found out that there is Chamfer Matching available in OpenCV. I can see there is a function chamferMatching() for C++ and there seems to be a way to use it in Python, too. However, I was unable to find how to use this feature in Java. I am using OpenCV 3.1 Where can I find it in the Java interface? Is it even available there?
If not, what can I use instead? I am trying to recognize fruits. For now apples in particular. I want to match precomputed apple contour to found contours in the image (chamfer matching). After finding a possible apple I am planning to use a classifier to make sure the color and texture are correct.
Template matching seems to be a bad choice because it doesn't work with recognizing rotated objects. I am wondering if I can use Feature Descriptors. Note that I am not trying to recognize a particular apple and I don't know if Feature Descriptors are good for this.
Any thoughts?
EDIT: Ok, I decided to use the findContours() function to get all of the contours in the image, then filter them by area and compare each of the filtered contours with others, designated as templates from training, using matchShapes(). I implemented this and it is not working right (because findContours() is not detecting the apple contours) but I'll post another question with this specific problem. Here I want to ask if this way sounds ok and if there is a better way to detect and compare contours.
Ok, I figured it out. There seems to be no Chamfer Matching in OpenCV. It is implemented in JavaCV and there is no sign of it in the native code. Since I'm using OpenCV for Java it is not a good solution for me.
This answer helped me a lot. It is in C++ but it can easily be written in Java.
Initially, I am training the program using a database of 100 images of green apples. The training is actually just storing the largest contour of every photo in a file.
The key to my problem was dividing the image into the 3 different channels resulting in 3 different grayscale images. I transform them using Canny and dilate. Now I check every one of them for contours and it is very likely I will detect the contours of the apple in at least one of them. Once I have all the contours from the 3 images, I filter them by size and then comparing them with every single contour from the training data. If the contour is close enough to one of them I assume it is a contour of an apple.
There seems to be quite a lot of false positives but they will be filtered out when my coleague implements the module doing checks for color and texture of the selected contours (their content).
Here's our project's repository if it would be of help to anyone.
Related
I have been working on face detection and i am able to detect frontal faces like all other people using the haarcascade xml files. My next task is to detect a side face (Non-Frontal). I am working in opencv. The profileface xml is not able to detect the side faces with accuracy. So i feel only option left is to make my own xml file which can detect side faces. Can anyone help me out?
Thanks
Did you try to combine the frontal and profile face recognition?
I was working with this as well, and the result was pretty good actually.
You also need to specify the min and max framesize as accurate as possible.
Unfortunately I did not find a side face haarcascade, so it looks like, you need to train your own one.
if you just want to test this out, you don't actually need so many pictures of faces.
You need a lot of negatives. Because opencv provides a function to generate positive pictures based on a single image of the face and a bunch of negative pictures.
To find the negative pictures you could simply take a video of the backgrounds where you want to detect the faces, and then just extract all the images form the video file. From only 3 minutes you get over 2000 images.
For the training I would recommend you to keep the size of all pictures very small, because otherwise it will take like forever to train the cascade file.
maybe you can see opencv Cascade Classifier Training for a reference. I didn't try it, but offer you for a reference.
website: http://docs.opencv.org/2.4/doc/user_guide/ug_traincascade.html
and there are some Q&A for training.
website: http://www.computer-vision-software.com/blog/2009/11/faq-opencv-haartraining/
I've not found anything here or on google. I'm looking for a way to identify shapes (circle, square, triangle and various other shapes) from a image file. Some examples:
You get the general idea. Not sure if BoofCV is the best choice here but it looks like it should be straightforward enough to use, but again I know nothing about it. I've looked at some of the examples and I though before I get in over my head (which is not hard to do some days), I thought I would ask if there is any info out there.
I'm taking a class on Knowledge Based AI solving Ravens Progressive Matrix problems and the final assignment will use strictly visual based images instead of the text files with attributes. We are not being graded on the visual since we only have a few weeks to work on this section of the project and we are encouraged to share this information. SOF has always been my go to source for information and I'm hoping someone out there might have some ideas on where to start with this...
Essentially what I want to do is detect the shapes (?? convert them into 2D geometry) and then make some assumptions about attributes such as size, fill, placement etc, create a text file with these attributes and then using that, send it through my existing code based that I wrote for my other projects to solve the problems.
Any suggestions????
There are a lot of ways you can do it. One way is to find the contour of the shape then fit a polygon to it or a oval. If you git a polygon to it and there are 4 sides with almost equal length then its a square. The contour can be found with binary blobs (my recommendation for the above images) or canny edge.
http://boofcv.org/index.php?title=Example_Fit_Polygon
http://boofcv.org/index.php?title=Example_Fit_Ellipse
I've got a ridiculously insane Linear Algebra professor at uni who asked us this last Friday to develop a programme in Java that loads a monochrome picture and then applies an edge-detecting filter on it.
The problem is nobody in my class has got the slightest clue how to do it and I have only a week to get it done.
As I'm still trying to get my head round it and start it from scratch, does anybody have anything ready to send me so I can study it and save my semester?
Any efforts will be much appreciated.
Here's a very basic approach you might go with:
1) What is an edge in a monochrome image? One could say that it is a steep intensity gradient. If you go from black to white that is an edge, and vice versa.
2) A very simple filter operation that builds on this idea is the Sobel operator. Read up on it here: Wikipedia.
3) You'll stumble across 2 terms that may be unfamiliar to you: Kernel and Convolution. A kernel is basically a window moved over each pixel, performing an operation on the pixel's environment. In case of the Sobel 3x3 kernel, you assign a new value to the filtered image based on the pixel's direct neighbours. The convolution operation can be thought of as - among other things - an operation that moves the kernel across every pixel in the image (note: This is a gross oversimplification to get you started and technically incorrect. It should, however, give you the right idea)
4) Now the simplest way of applying a Sobel kernel to a BufferedImage is by using the ConvolveOp class. It is a prebuilt java class that takes a kernel, applies it to a given image and returns the filtered image. However, if this is for class, you might want to implement this yourself.
I have an image where I want to find a specific location (coordinate) based on its color. For example
I want to find coordinates of edges of this Black box.
How can i detect Black color in this image in Java?
Note: My target is to develop a program to detect eyes in a face
I would suggest using threshold filter and then convert image to 1-bit format. This should do the trick.
However locating eyes in image is much more harder. You might be interested in open source OpenCV library. Here is port dedicated for Java - javacv. And C++ example of face detection using OpenCV.
as far as I know Fourier transform is used in image processing. With that you get your picture in frequency domain that represents a signal (in case of image signal is two dimensional). You can use Fast Fourier Transform algorimth (FFT in java, Fun with Java, Understanding FFT). There's a lot of papers about eye detection issue you can read and take inspiration from:
http://www.jprr.org/index.php/jprr/article/viewFile/15/7
http://people.ee.ethz.ch/~bfasel/papers/avbpa_face.pdf
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.117.2226&rep=rep1&type=pdf
Here’s my task which I want to solve with as little effort as possible (preferrably with QT & C++ or Java): I want to use webcam video input to detect if there’s a (or more) crate(s) in front of the camera lens or not. The scene can change from "clear" to "there is a crate in front of the lens" and back while the cam feeds its video signal to my application. For prototype testing/ learning I have 2-3 images of the “empty” scene, and 2-3 images with one or more crates.
Do you know straightforward idea how to tackle this task? I found OpenCV, but isn't this framework too bulky for this simple task? I'm new to the field of computer vision. Is this generally a hard task or is it simple and robust to detect if there's an obstacle in front of the cam in live feeds? Your expert opinion is deeply appreciated!
Here's an approach I've heard of, which may yield some success:
Perform edge detection on your image to translate it into a black and white image, whereby edges are shown as black pixels.
Now create a histogram to record the frequency of black pixels in each vertical column of pixels in the image. The theory here is that a high frequency value in the histogram in or around one bucket is indicative of a vertical edge, which could be the edge of a crate.
You could also consider a second histogram to measure pixels on each row of the image.
Obviously this is a fairly simple approach and is highly dependent on "simple" input; i.e. plain boxes with "hard" edges against a blank background (preferable a background that contrasts heavily with the box).
You dont need a full-blown computer-vision library to detect if there is a crate or no crate in front of the camera. You can just take a snapshot and make a color-histogram (simple). To capture the snapshot take a look here:
http://msdn.microsoft.com/en-us/library/dd742882%28VS.85%29.aspx
Lots of variables here including any possible changes in ambient lighting and any other activity in the field of view. Look at implementing a Canny edge detector (which OpenCV has and also Intel Performance Primitives have as well) to look for the outline of the shape of interest. If you then kinda know where the box will be, you can perhaps sum pixels in the region of interest. If the box can appear anywhere in the field of view, this is more challenging.
This is not something you should start in Java. When I had this kind of problems I would start with Matlab (OpenCV library) or something similar, see if the solution would work there and then port it to Java.
To answer your question I did something similar by XOR-ing the 'reference' image (no crate in your case) with the current image then either work on the histogram (clustered pixels at right means large difference) or just sum the visible pixels and compare them with a threshold. XOR is not really precise but it is fast.
My point is, it took me 2hrs to install Scilab and the toolkits and write a proof of concept. It would have taken me two days in Java and if the first solution didn't work each additional algorithm (already done in Mat-/Scilab) another few hours. IMHO you are approaching the problem from the wrong angle.
If really Java/C++ are just some simple tools that don't matter then drop them and use Scilab or some other Matlab clone - prototyping and fine tuning would be much faster.
There are 2 parts involved in object detection. One is feature extraction, the other is similarity calculation. Some obvious features of the crate are geometry, edge, texture, etc...
So you can find some algorithms to extract these features from your crate image. Then comparing these features with your training sample images.