Plotting data cubes - view

Is there a way to plot data cubes with any kind of program? In order to plot this (1) image, I had to use TinkerCard, that by the way doesn't allow to put names along the data cube dimensions. Is there any kind of tool that allows do do something similar to (2) or (3)? Thanks in advance

I think this is a not possible.
The cubes which I play with all have atleast 10 dimensions.
The problem is that the short name, olap cube, suggests that some sort of pictorial representation is possible.
I think it is maybe better to remeber them using the fuller name multi-dimensional cubes.
Once past 3 dimensions I don't understand how it will be possible to draw a representative picture.
Saying all the above I have a book co-authored by Mosha Pasumadsky which contains some simple cube pictures similar to your picture. Also I attended a course run by Chris Webb and he used pictures of cubes to help our understanding. The pictures they have used are all very simplified, and of only small spaces within a full cube.

Related

Matlab or ImageJ or Fiji image stitching

Looking for help in solving this problem. I understand how stitching works on Matlab and Fiji but what I have is a very particular case. I want to stich an series of images together. So the easiest way to describe it is lets say I am walking down a long street with a repeating pattern of buildings on both sides. So I snap a picture facing down the street which makes the buildings kind of in the Peripheral view. So I move a set number of steps and take another picture and so on and so forth. How would I stich these photos together using Fiji or Matlab.

Algorithms for finding a look alike face?

I'm doing a personal project of trying to find a person's look-alike given a database of photographs of other people all taken in a consistent manner - people looking directly into the camera, neutral expression and no tilt to the head (think passport photo).
I have a system for placing markers for 2d coordinates on the faces and I was wondering if there are any known approaches for finding a look alike of that face given this approach?
I found the following facial recognition algorithms:
http://www.face-rec.org/algorithms/
But none deal with the specific task of finding a look-alike.
Thanks for your time.
I believe you can also try searching for "Face Verification" rather than just "Face Recognition". This might give you more relevant results.
Strictly speaking, the 2 are actually different things in scientific literature but are sometimes lumped under face recognition. For details on their differences and some sample code, take a look here: http://www.idiap.ch/~marcel/labs/faceverif.php
However, for your purposes, what others such as Edvard and Ari has kindly suggested would work too. Basically they are suggesting a K-nearest neighbor style face recognition classifier.
As a start, you can probably try that. First, compute a feature vector for each of your face images in your database. One possible feature to use is the Local Binary Pattern (LBP). You can find the code by googling it. Do the same for your query image. Now, loop through all the feature vectors and compare them to that of your query image using euclidean distance and return the K nearest ones.
While the above method is easy to code, it will generally not be as robust as some of the more sophisticated ones because they generally fail badly when faces are not aligned (known as unconstrained pose. Search for "Labelled Faces in the Wild" to see the results for state of the art for this problem.) or taken under different environmental conditions. But if the faces in your database are aligned and taken under similar conditions as you mentioned, then it might just work. If they are not aligned, you can use the face key points, which you mentioned you are able to compute, to align the faces. In general, comparing faces which are not aligned is a very difficult problem in computer vision and is still a very active area of research. But, if you only consider faces that look alike and in the same pose to be similar (i.e. similar in pose as well as looks) then this shouldn't be a problem.
The website your gave have links to the code for Eigenfaces and Fisherfaces. These are essentially 2 methods for computing feature vectors for your face images. Faces are identified by doing a K nearest neighbor search for faces in the database with feature vectors (computed using PCA and LDA respectively) closest to that of the query image.
I should probably also mention that in the Fisherfaces method, you will need to have "labels" for the faces in your database to identify the faces. This is because Linear Discriminant Analysis (LDA), the classification method used in Fisherfaces, needs this information to compute a projection matrix that will project feature vectors for similar faces close together and dissimilar ones far apart. Comparison is then performed on these projected vectors. Here lies the difference between Face Recognition and Face Verification: for recognition, you need to have "labels" your training images in your database i.e. you need to identify them.
For verification, you are only trying to tell whether any 2 given faces are of the same person. Often, you don't need the "labelled" data in the traditional sense (although some methods might make use of auxiliary training data to help in the face verification).
The code for computing Eigenfaces and Fisherfaces are available in OpenCV in case you use it.
As a side note:
A feature vector is actually just a vector in your linear algebra sense. It is simply n numbers packed together. The word "feature" refers to something like a "statistic" i.e. a feature vector is a vector containing statistics that characterizes the object it represents. For e.g., for the task of face recognition, the simplest feature vector would be the intensity values of the grayscale image of the face. In that case, I just reshape the 2D array of numbers into a n rows by 1 column vector, each entry containing the value of one pixel. The pixel value here is the "feature", and the n x 1 vector of pixel values is the feature vector. In the LBP case, roughly speaking, it computes a histogram at small patches of pixels in the image and joins these histograms together into one histogram, which is then used as the feature vector. So the Local Binary Pattern is the statistic and the histograms joined together is the feature vector. Together they described the "texture" and facial patterns of your face.
Hope this helps.
These two would seem like the equivalent problem, but I do not work in the field. You essentially have the following two problems:
Face recognition: Take a face and try to match it to a person.
Find similar faces: Take a face and try to find similar faces.
Aren't these equivalent? In (1) you start with a picture that you want to match to the owner and you compare it to a database of reference pictures for each person you know. In (2) you pick a picture in your reference database and run (1) for that picture against the other pictures in the database.
Since the algorithms seem to give you a measure of how likely two pictures belong to the same person, in (2) you just sort the measures in decreasing order and pick the top hits.
I assume you should first analyze all the picture in your database with whatever approach you are using. You should then have a set of metrics for each picture which you can compare a specific picture with and statistically find the closest match.
For example, if you can measure the distance between the eyes, you can find faces that have the same distance. You can then find the face that has the overall closest match and return that.

Making 3D representation of an object with a webcam

Is it possible to make a 3D representation of an object by capturing many different angles using a webcam? If it is, how is it possible and how is the image-processing done?
My plan is to make a 3D representation of a person using a webcam, then from the 3D representation, i will be able to tell the person's vital statistics.
As Bart said (but did not post as an actual answer) this is entirely possible.
The research topic you are interested in is often called multi view stereo or something similar.
The basic idea resolves around using point correspondences between two (or more) images and then try to find the best matching camera positions. When the positions are found you can use stereo algorithms to back project the image points into a 3D coordinate system and form a point cloud.
From that point cloud you can then further process it to get the measurements you are looking for.
If you are completely new to the subject you have some fascinating reading to look forward to!
Bart proposed Multiple view geometry by Hartley and Zisserman, which is a very nice book indeed.
As Bart and Kigurai pointed out, this process has been studied under the title of "stereo" or "multi-view stereo" techniques. To be able to get a 3D model from a set of pictures, you need to do the following:
a) You need to know the "internal" parameters of a camera. This includes the focal length of the camera, the principal point of the image and account for radial distortion in the image.
b) You also need to know the position and orientation of each camera with respect to each other or a "world" co-ordinate system. This is called the "pose" of the camera.
There are algorithms to perform (a) and (b) which are described in Hartley and Zisserman's "Multiple View Geometry" book. Alternatively, you can use Noah Snavely's "Bundler" http://phototour.cs.washington.edu/bundler/ software to also do the same thing in a very robust manner.
Once you have the camera parameters, you essentially know how a 3D point (X,Y,Z) in the world maps to an image co-ordinate (u,v) on the photo. You also know how to map an image co-ordinate to the world. You can create a dense point cloud by searching for a match for each pixel on one photo in a photo taken from a different view-point. This requires a two-dimensional search. You can simplify this procedure by making the search 1-dimensional. This is called "rectification". You essentially take two photos and transform then so that their rows correspond to the same line in the world (simplified statement). Now you only have to search along image rows.
An algorithm for this can be also found in Hartley and Zisserman.
Finally, you need to do the matching based on some measure. There is a lot of literature out there on "stereo matching". Another word used is "disparity estimation". This is basically searching for the match of pixel (u,v) on one photo to its match (u, v') on the other photo. Once you have the match, the difference between them can be used to map back to a 3D point.
You can use Yasutaka Furukawa's "CMVS" or "PMVS2" software to do this. Or if you want to experiment by yourself, openCV is a open-source computer vision toolbox to do many of the sub-tasks required for this.
This can be done with two webcams in the same ways your eyes work. It is called stereoscopic vision.
Have a look at this:
http://opencv.willowgarage.com/documentation/camera_calibration_and_3d_reconstruction.html
An affordable alternative to get 3D data would be the Kinect camera system.
Maybe not the answer you are hoping for but Microsoft's Kinect is doing that exact thing, there are some open source drivers out there that allow you to connect it to your windows/linux box.

image feature identification

I am looking for a solution to do the following:
( the focus of my question is step 2. )
a picture of a house including the front yard
extract information from the picture like the dimensions and location of the house, trees, sidewalk, and car. Also, the textures and colors of the house, cars, trees, and sidewalk.
use extracted information to generate a model
How can I extract that information?
You could also consult Tatiana Jaworska research on this. As I understood, this details at least 1 new algorithm to feature extraction (targeted at roofs, doors, ...) by colour (RGB). More intriguing, the last publication also uses parameterized objects to be identified in the house images... that must might be a really good starting point for what you're trying to do.
link to her publications:
http://www.springerlink.com/content/w518j70542780r34/
http://portal.acm.org/citation.cfm?id=1578785
http://www.ibspan.waw.pl/~jaworska/TJ_BOS2010.pdf
Yes. You can extract these information from a picture.
1. You just identify these objects in a picture using some detection algorithms.
2. Measure these objects dimensions and generate a model using extracted information.
well actually your desired goal is not so easy to achieve. First of all you'll need a good way to figure what what is what and what is where on your image. And there simply is no easy "algorithm" for detecting houses/cars/whatsoever on an image. There are ways to segment different objects (like cars) from an image, but those don't work generally. Especially on houses this would be hard since each house looks different and it's hard to find one solid measurement for "this is house and this is not"...
Am I assuming it right that you are trying to simply photograph a house (with front yard) and build a texturized 3D-model out of it? This is not going to work since you need several photos of the house to get positions of walls/corners and everything in 3D space (There are approaches that try a mesh reconstruction with one image only but they lack of depth information and results are fairly poor). So if you would like to create 3D-mdoels you will need several photos of different angles of the house.
There are several different approaches that use this kind of technique to reconstruct real world objects to triangle-meshes.
Basically they work after the principle:
Try to find points in images of different viewpoint which are the same on an object. Considering you are photographing a house this could be salient structures likes corners of windows/doors or corners or edges on the walls/roof/...
Knowing where one and the same point of your house is in several different photos and knowing the position of the camera of both photos you can reconstruct this point in 3D-space.
Doing this for a lot of equal points will "empower" you to reconstruct the shape of your house as a 3D-model by triangulating the points.
Taking parts of the image as textures and mapping them on the generated model would work as well since you know where what is.
You should have a look at these papers:
http://www.graphicon.ru/1999/3D%20Reconstruction/Valiev.pdf
http://people.csail.mit.edu/wojciech/pubs/LabeledRec.pdf
http://people.csail.mit.edu/sparis/publi/2006/oceans/Paris_06_3D_Reconstruction.ppt
The second paper even has an example of doing exactly what you try to achieve, namely reconstruct a textured 3D-model of a house photographed from different angles.
The third link is a powerpoint presentation that shows how the reconstruction works and shows the drawbacks there are.
So you should get familiar with these papers to see what problems you are up to... If you then want to try this on your own have a look at OpenCV. This library provides some methods for feature extraction in images. You then can try to find salient points in each image and try to match them.
Good luck on your project... If you have problems, please keep asking!
I suggest to look at this blog
https://jwork.org/main/node/35
that shows how to identify certain features on images using a convolutional neural network. This particular blog discusses how to identify human faces on images from a large set of random images. You can adjust this example to train neural network using some other images. Note that even in the case of human faces, the identification rate is about 85%, therefore, more complex objects can be even harder to identify

Computer Science Theory: Image Similarity

So I'm trying to run a comparison of different images and was wondering if anyone could point me in the right direction for some basic metrics I can take for the group of images.
Assuming I have two images, A and B, I pretty much want as much data as possible about each so I can later programmatically compare them. Things like "general color", "general shape", etc. would be great.
If you can help me find specific properties and algorithms to compute them that would be great!
Thanks!
EDIT: The end goal here is to be able to have a computer tell me how "similar" too pictures are. If two images are the same but in one someone blurred out a face; they should register as fairly similar. If two pictures are completely different, the computer should be able to tell.
What you are talking about is way much general and non-specific.
Image information is formalised as Entropy.
What you seem to be looking for is basically feature extraction and then comparing these features. There are tons of features that can be extracted but a lot of them could be irrelevant depending on the differences in the pictures.
There are space domain and frequency domain descriptors of the image which each can be useful here. I can probably name more than 100 descriptors but in your case, only one could be sufficient or none could be useful.
Pre-processing is also important, perhaps you could turn your images to grey-scale and then compare them.
This field is so immensely diverse, so you need to be a bit more specific.
(Update)
What you are looking for is a topic of hundreds if not thousands of scientific articles. But well, perhaps a simplistic approach can work.
So assuming that the question here is not identifying objects and there is no transform, translation, scale or rotation involved and we are only dealing with the two images which are the same but one could have more noise added upon it:
1) Image domain (space domain): Compare the pixels one by one and add up the square of the differences. Normalise this value by the width*height - just divide by the number of pixels. This could be a useful measure of similarity.
2) Frequency domain: Convert the image to frequency domain image (using FTT in an image processing tool such as OpenCV) which will be 2D as well. Do the same above squared diff as above, but perhaps you want to limit the frequencies. Then normalise by the number of pixels. This fares better on noise and translation and on a small rotation but not on scale.
SURF is a good candidate algorithm for comparing images
Wikipedia Article
A practical example (in Mathematica), identifying corresponding points in two images of the moon (rotated, colorized and blurred) :
You can also calculate sum of differences between histogram bins of those two images. But it is also not a silver bullet...
I recommend taking a look at OpenCV. The package offers most (if not all) of the techniques mentioned above.

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