Can anyone tell me how to detect faces in a static picture using Ruby or Javascript?
If you are going to try and write something from scratch, there is a great explanation of the process on the Carnegie Mellon Website - neat graphics too.
However, your best bet is probably trying to hook into the Opensource Computer Vision project. Here is a good tutorial on using OpenCV for facial recognition.
Since the other answers to that interesting question are mostly outdated now, here the 2012 solution:
Using jQuery with jquery.objectdetect:
$("#faces").objectdetect("all", {classifier: objectdetect.frontalface}, function(coords) {
// Do something with the face coordinates
});
Using jQuery with jquery.facedetection:
var coords = $("#faces").faceDetection();
// Do something with the face coordinates
Not using jQuery: Both plugins are based on stand-alone libraries that do not depend on jQuery at all.
In reply to #joeforker who said
"If you really don't understand that the notion JQuery can detect
faces is a joke, you need to learn a lot before you will be ready to
detect faces."
Or you just have to wait a year or two ;)
It looks like you are new to programming. Perhaps you have an advanced mathematics degree? If you really don't understand that the notion JQuery can detect faces is a joke, you need to learn a lot before you will be ready to detect faces. If you're lucky you can find an easy out-of-the-box solution. Unfortunately, face recognition is in the class of problems that tend to lack easy out of the box solutions. JavaScript is right out.
http://rubyforge.org/projects/opencv/ is a Ruby binding to OpenCV. The pitiful documentation (autogenerated API docs only) at http://doc.blueruby.mydns.jp/opencv/ mentions a face_detect.rb that might be helpful. As with most bindings, you should also consult the documentation for the original library e.g. http://opencv.willowgarage.com/wiki/FaceDetection
You should also understand that face detection (where are the faces in this photo?) is a different and easier problem than face recognition (whose face is it).
I do not know if this question was properly answered or how you resolved it, but I recently encountered this problem myself. I'm currently investigating external API's to implement my solution. The two Ruby API's that I am currently comparing are rdetection and Face.com's API
I'm primarily using it for face-aware image-crop using ImageMagick, so your needs and results may differ.
Detecting faces reliably is one of the hard problems in Computer Science. Realistically, there's no practical way for you to do it using Ruby, JavaScript or any other application language using current technology. If you tell us why you need to detect faces then we might be able to suggest a practical alternative approach.
Collect a lot of cash and contact these guys for a good solution!
Wikipedia has a good article about this which also explains why you're trying to do something that is still extremely complex to do.
FRGC is also interesting... If you do find a solution, you can take part in this challenge.
This is a face recognition tutorial using Javascript and face recognition APIs using Mashape - http://blog.mashape.com/post/45712257463/face-recognition-using-javascript-and-mashape
It also lets you detect if the person is smiling or not :)
After some research and help from this thread I've decided to make a rubygem which can be found here:
EDIT:
Unfortunately rekognize decided to discontinue their services making this Gem obsolete.
This uses the face recognition API from rekognition.com.
Javascript Neural Nets have been used for OCR so should be possible if much harder for faces.
Face detection is done using intensive memory based algorithms, which actually go through the image data to detect face like patterns. They may be many facial recognition / Pattern recoginition algorithms and APIS available for free (or for a fee) which you can use/implement with Ruby or Javascript.
I know this is an old question, but if anyone happens on it like I did check these out: blog post, test page, and Github.
This should get you started. It's about using OpenCV with Ruby via FFI: http://rubysource.com/detecting-faces-with-ruby-ffi-in-a-nutshell/
Related
I have completed codeacademy twice, freecodecamp twice and read a few online articles...I believe I now have a good understanding of the fundamentals of Javascript.
However, I feel lost in terms of where to go next. People say build projects, but where do I start? How do I plan? Even though I know the fundamentals of Javascript, I still feel there is a lot to learn. I feel like I will only truly start understanding Javascript once I start putting projects together but I cant think of any.
Also, codeacademy, freecodecamp and these other online course websites dont seem to really teach DOM manipulation. Is there any online coding sites, similar to the ones mentioned, which will allow me to practice DOM manipulation?
I would be hufely grateful if people who have developed their understanding in Javascript can give me some advice based on how they did it.
I am just sitting here staring at my laptop and going back and forth. I cant really seem to figure out what to do next, now that I have gained a basic understanding of the core concepts of Javascript. Please guys, help!
This is not a very good question, but I still would like to try and explain.
Questions you need to ask yourself
Frontend or backend js?
I assume frontend based on the "DOM manipulation" part, but there is also Node.js for the backend with it's own unique API to use and interact with the operating system.
Do I want to use libraries and/or frameworks
Depending on your needs and preferences you will come in touch with these things, they all have their own learning curve, on top of learning js. Libraries are mostly just function in order to help you. However frameworks like Vue and Angular require a way of writing your code that is like it's own language. (opinionated)
What version(s) of js and browsers do you want to support?
Javascript has evolved over time and the javascript engines in browsers as well. Older IE browsers will be harder to support without the help of a library like jQuery.
Now about the learning part and where you can practice.
There are probably thousands of great sites to practice, however I will give you my favorites.
The stackoverflow documentation on javascript (top navigation on this page)
I will get hate for this: W3Schools
To read the docs on Mozilla
interactive on both codeschool and codeacademy
JSFiddle for practicing in a closed environment
https://bento.io/topic/javascript
https://learnxinyminutes.com/docs/javascript/
http://www.allitebooks.com/ for specific ebooks
Have a look at what frameworks are popular nowadays and why. If they suit your needs. Learn them one or two at a time but not more, so you won't mix them all up in the end. Try to at least understand OOP in javascript even if you don't intend to use it later. Anyone feel free to expand this answer because it is hard to cover it all myself.
I am new to computer programming and have some experience programming with python. I am thinking of developing a program that does physics simulations (projectiles, circular motion, damped simple harmonic motion systems etc.) as a hobby project. I would like to write the program that it could be run by a non-technical user(my fellow students) on a variety of platforms (mac, windows etc.) without any setup and python doesn’t seem to be a good option for building such a program so I am looking for an alternative. JavaScript has caught my attention, as it seems to be quite powerful on modern browsers, especially in conjunction with HTML5. I would like to know whether it is suitable to use JavaScript for this type application, and some information as to where I should start (I have no JavaScript knowledge)
Thanks in advance!
Yes I did have a look at the similar threads on the site but I want write something by myself than using a 3rd party library (other than for the frontend, if possible) :)
What is actually your question? :)
Can you write a physics simulation in Python?
Yes, of course.
Can you write a physics simulation in Javascript?
Yup.
Will it be useful?
Yes, probably.
Will it be efficient?
Not as efficient as an implementation with C, to be sure. But for small-scale simulations should you should have quite enough power with current JIT javascript interpreters. Tens or hundreds of objects on 30fps looks like a safe approximation, I think.
Can you make use of modern HTML when writing a physics simulation in JS?
The simulation and the display are two different things, but yes, if you want to make a graphics frontend to your simulation, the modern features of HTML and CSS could be certainly useful. But if you write it in any other language, you still have nice choices for visualization.
How to learn JavaScript?
There's plenty of tutorials online, but I don't know any particular one to recommend; perhaps anyone else can fill for me here.
As mentioned by Kos languages that are as High Level as Python or Javascript might constrain you. But later on you can still move critical parts to C-Code. (-> Regular shared Library or even Browser-Plugin)
For JavaScript I recommend you the Mozilla tutorials: https://developer.mozilla.org/en/javascript
Check out the "JavaScript Guide" in particular and keep in mind that not every Browser supports JavaScript 1.7. By the way, you should also checkout jQuery. Actually it might be easier to start right off with jQuery because you need some highlevel library anyways.
By the way: You might also want to check out Processing. (www.processing.org) It might be perfect for you as you are new to programming and it has a lot of awesome vizualization features. It basically a simplified Java with a very easy to use library. You can checkout the pre-installed examples and start playing around. Be sure to check the Reference on the website / the forum if you are stuck with problems. Processing runs on the JVM and is therefore cross plattform.
I recommend Processing very much because you can directly see results and in any case it might be interesting for Prototyping even if you think of using another language in the future to suit your needs.
Actually there is even a JavaScript version of Processing though I never used it...
EDIT: If you plan to choose JavaScript, you should use Firefox in combination with Firebug. It makes life easier when debugging...
It seems that many of the JavaScript questions are answered by the simple use of pushing a library, without taking into account the person asking the question. I think libraries are great myself, but sometimes I think that we're too quick to throw a library down someone's throat.
Imagine a person asks a question and it's apparent that they barely know JavaScript. They're just using code they found and piecing it together with other code, and really have no firm foundation to work on. To add a library on top of that flimsy foundation seems like a disaster waiting to happen.
With that in mind, what JavaScript / programming / web browser concepts do you think are necessary to understand before a library/framework is introduced to a person? Should a framework / library be part of the learning process?
I don't think someone has to grasp absolutely everything to use a library, I just think some people would be better served with a "Library X might help solve your problems, but before you do that, you might want to read up on the following concepts", rather than just a "use library x" answer.
What you should learn are some fundamental programming techniques:
closures
continuations
function objects / what a "first class" function is
JavaScript object oriented design
difference between "prototype" languages and traditional Object Oriented languages
Absolutely firm grounding in HTML and CSS: standards, tricks, and various browser compatibility issues
UI Design Principals
With that in mind, today its practically impossible to develop without a library. I recommend Dojo but others use jQuery, YUI, etc...
When choosing a library, you need to have a firm understanding of what problem you are trying to solve. Is it browser abstraction? dealing with communication? charting? animations? graphics? UI toolkits?
Each library has its "niche", so you need to really know what you're specific problem domain is and in turn choose a library accordingly.
I would suggest using the brick and mortar kind of library and find a good book on JavaScript.
I think that one reflex reaction to a "how do implement X" is "don't reinvent then wheel", and this is generally good advice. I think that if you have to ask how to do something reasonably complex, and it's already in a library then you're going to waste massive time trying to piece together something from a few answers on SO.
So barring the obvious: learn the syntax of the language, learn how to debug etc., by and large a library is the right answer. And that's not just to say "Use the library, disengage brain" it also means "Study the library, look at the issues it's solving - you didn't realise your problem was so complex? Well the folks who put hours and days into the library studied the problem in some detail and probably developed the library by using it extendsively. Study the implementation and learen how."
I think that studying good code is a very good way to learn.
Libraries bring similarities to browsers where so much is different from browser to browser. This is why, I'd suspect, people suggest their usage in various answers. Nothing is stoping anyone from reading a good js book if they want to actually understand what is going on, but we surely cannot shove books and tutorials down anyone's throat. You need to want to learn before that would be worth anything.
They should read this http://www.amazon.com/exec/obidos/ASIN/0596517742/wrrrldwideweb
And check out some of the links here http://www.crockford.com/
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First, a little background: I have written a little application in python with SQLAlchemy, which is roughly an improved RSS reader: it selects links that should interest the user, and shows them to him. I already have a very simple command-line interface, and I envision a variety of interfaces: web, instant-messaging, desktop...
For now I'd like to create a simple web interface, but I have absolutely zero experience in the matter (appart from making a simple php forum 5 or 6 years ago...). So I'm comming here for advice on where to start:
Is there a good tutorial on HTML/CSS/Javascript focused on making a website look good simply? I know about w3schools, but it's a terrible tutorial IMHO, since it teaches you about HTML/CSS but doesn't show you how to use them.
Should I use a javascript library? Which one?
Should I use a web framework? I'm guessing either not or a very lightweight one, since I already have an application core with a database and SQLAlchemy, and I don't want to drop it.
Any other advice?
Thanks!
I recommend that you use some kind of web framework, it will make things a lot easier. Since you already know Python you should look into Django framework. It seems that you can use SQLAlchemy with Django, see djange-sqlalchemy project.
I recommend using JQuery framework/library for Javascript stuff. It greatly simplifies coding and takes care of most web browser incompabilities.
This CSS tutorial seems to give you the basics.
I would start by reading the Django tutorial and start trying things out. I wouldn't worry too much about HTML stuff, you should be able to pick up enough from Django tutorial. Make your site first functional with HTML, Django and SQLAlchemy. Only then start worring about Javascript. Who knows, maybe you do not need Javascript at all?
Do not try make your site work and look good at the same time. When you are making your site work, use simple and ugly HTML pages. When you are making you web site look good, work only with static HTML pages and CSS files. It is easier to combine the two in the end.
Just like everyone else here, I'll chime in with "Use my favorite framework, because it's what I use...."
I would start with small goals for a web interface. Get something simple up and running that to make sure you understand how things work.
Write an app that responds to the following url and returns something.
http://localhost:8000/my_links
Once you understand the little bit of machinery it takes to make that possible, what is handed to you as far as information about the request, and what you need to produce to return to the caller, it should be come clear how to fill in the blanks to get from your existing application to data thrown at the web browser.
Learn WSGI for no other reason than most of the libraries that will help you build a web application utilize this to some degree.
One of the links from the above page that I found extremely beneficial in understanding how all this works. was Ian Bickings article "A Do-it Yourself Framework"
Once you get a grasp of that stuff, you may find that dealing with WSGI at such a low level is maybe a little too cumbersome. That's when you'll probably want something like WebOb
which is just one of several ways people have come up with for abstracting away the low level details of the request/response cycle into some convenient objects. In a sense encompassing the HTTP protocol without trying to make it make sense to someone who doesn't want to know what HTTP is.
Depending on the complexity of your application you may decide that handling a request, looking at the path and dispatching off to one of many functions is a drag you'd rather not deal with. This is where everyone's favorite framework starts to be beneficial. And I would suspect that you would know enough by this point to better assess the frameworks that are out there and determine which fits your needs and goals.
Lots prefer django, maybe you will too. Others prefer Turbogears, and or Pylons, maybe bfg, maybe grok, maybe zope, maybe plone. But no one here knows what you want your application to do.
It's an interestingly common mistake: all of the above answers provide technological advise on what's the best technology to do ... what exactly? You should work the other way around.
I think that if you want your application to be successful, you have to make sure it enables its users to get the most out of it in the most natural way to them.
Therefore, i suggest you first "storyline" how things should happen from a user's perspective. Use paper and pen, or more sophisticated wireframing tools such as balsamiq mockups.
So, first lay out what the experience should be, and this will tell you which technology will be the best choice to enable that experience.
Oh, and don't forget to read this.
HTML, CSS and JS Book: DHTML and CSS for the World Wide Web
Javascript Library: JQuery
Web Framework: Not sure, DJango?
Other Advice: Learn to write HTML, CSS, and JS in a a simple text editor with syntax highlighting. Complex IDE's are cool, but for this stuff, they will make you learn slower.
Web applications are not simple.
HTML and CSS: Head First HTML is probably a good starting point. The Head First series are usually excellent tutorials. As Josh said, write your pages by hand.
Javascript: you don't need this to get started. Maybe in a later version. When you have a better idea what you'll need Javascript for, you'll be better equipped to pick a library that suits your needs.
Web framework: You should probably start with Django. That's the opposite of a "very lightweight" framework, but in this context "lightweight" requires more expertise to make something polished. So it's a good idea to aim for "feature rich and well supported" instead.
Here is another option, I feel it's worth mentioning before making any decision.
As web framework I would advise web2py, it is very easy to setup and yet powerful. Here is a document showing the differences between Django, web2py and some others. It is somewhat old but will give you a good overview.
Since you have legacy code, if you really want to keep it there is a fair compatibility between the two although you should double-check. The easiest would be to adapt your code, of course, the differences aren't so big. But that's your call :-)
Regarding the Javascript library, probably jQuery.
The best introduction you could follow is the opera web standards curriculum. Some of the information will be too basic - but a full understanding of all the topics covered will give you a very good grounding.
http://www.opera.com/company/education/curriculum/
Alternatively team up with someone who specialises in front-end development.
I am a .NET webdev using ASP.NET, C# etc... I "learned" javascript in college 5+ years ago and can do basic jobs with it. But I wonder if it is useful to become proficient in it.
Why should I learn Javascript?
Is it more advantageous then learning JQuery or a different library?
Yes, definitely learn Javascript before you learn one of the libraries about. It's the whole walk-before-you-can-run thing.
Make sure you add these sites to your bookmarks:
Mozilla's developer site: This contains the reference to the Javascript API in Mozilla. This will help you make sure you're writing code that Firefox understands.
IE's site in Microsoft Developer Network: The same, for IE.
W3's reference of DOM for HTML: In most web applications today, the Javascript code manipulates the DOM, which is an internal keeping track of the objects displayed on screen (but you already knew that, right ?) This is the reference to the DOM API. It is language neutral, which means it does not target Javascript, but these methods exist in Javascript too.
Douglas Crockford' site: Doug Crockford is THE MAN when it comes down to Javascript. The articles in his page are a must read. Because Javascript has closures and first-class functions, he believes it is closer to Lisp and Scheme than to other languages. And he teaches you how to greatly improve your code with these language features.
Yahoo Developer network: You may also want to check this. I'm not a regular visitor to this site, though, so I can't really say much about it.
Yes, absolutely you should learn JavaScript if you are doing web development. I highly recommend JavaScript: The Good Parts, by Doug Crockford. And, JQuery is a great framework to use (this site uses it) -- it kind of depends on what you are trying to do -- YUI and ExtJS are also very nice.
The answer is simple.
Hands down yes. There's a reason that Google have made such a big fuss about the V8 JS engine for Chrome, why Mozilla are working on TraceMonkey for Firefox and why Webkit have been working on Squirrelfish for a while (now Squirrelfish extreme). It's because JS is becoming more popular by the day.
Javascript is one of those languages that spending a few hours learning will probably teach you 99% of what you will ever really use. I would imagine you are at the point in your learning of javascript that you know more than enough now and just learn one or more of the frameworks now.
I would recommend brushing up on your non-frameworked javascript first. Refreshing/learning basic concepts of dom manipulation and what not. Like learning how to build a linked list, stack or queue in C++ before learning how to use the STL (standard template libraries).
In addition to brushing up on straight javascript, it might be good to get into a framework that doesn't abstract and change the way things work so much, for instance Prototype. You code with it very much the same way you code with straight javascript. Read through the Prototype code, learn how to make classes, and do some fancy stuff. From experience, I can say reading through the Prototype.js helped me learn alot.
After messing around a bit, then I'd say go for jQuery. If jQuery didn't, literally, change the way you write code I'd say go for it first, but learning how to build classes and js inheritance and what not can be a very important lesson for someone who wants to become fluent in JS.
Learning javascript is recommended for any web application developer. Why?
You will better understand the possibilities, limitations and dangers related to developing a web application
It is a boost for your career, if you are working on a web application that has a user interface.
However, learning javascript is usually a trade-off between a programming language and another. You should consider whether javascript is relevant for your career or project.
Unless you want to really get into javascript, I think you'd be better off learning enough JS to leverage one of the tried and tested javascript libraries out there.
One thing nice about JavaScript is that it is quite different from mainstream languages such as C#, VB.NET or Java. Learning it, especially if you have occasions to use it, will give you another insight on programming, and that's always good. I think it's worth learning it.
If you are doing web development then at some point you are going to get exposed to Javascript or ECMAScript at some point in your career for any one of a number of reasons. At a minimum you should know enough Javascript to be able to be able to validate user input; however, the web is moving in the direction of using more an more Ajax so you should also know enough Javascript to properly leverage one of the major libraries out there such as jQuery.
As some of the other users have noted, you can learn most of what you need of Javascript on a day to day basis in a single day or a couple of afternoons. If you want to get more advanced with Javascript then you are going to have to invest much more time in learning the language but odds are that unless you seek out this type of work that you are not going to encounter something that a preexisting library doesn't already exist for.
If all you want is to do some simple UI-effects and the like, I suggest you just pick a library and go for it!
Using libraries eliminates all the flawed implementations of JavaScript and provides you with an API which is the same across all browsers. And if you're working together with others it is also a great way of implementing code-standards and best practices.
Learning a second programming language is always good.
By the sound of it, JavaScript is a language that you use, to it will be of practical use too. As a web dev, it has been recommended to me in a review that i learn at least basic JavaScript.
A library such as jQuery is essential for web development thse days, so you could learn that too.
I don't think a lot of deliberate learning makes sense (but of course you need some basic knowledge), but I also think after some years of web development you'll become pretty proficient in the language anyway :)
If you are a webdev then yes, you should be proficient with Javascript. Javascript is a major part of making web apps as interactive as desktop apps.
With that being said, learn to use one of the cross-browser compatible libraries like JQuery, Prototype, etc. We do not need to have any more single browser crud created using Javascript, just because any real man/woman rolls their own.
A few things to learn in Javascript:
1. Basic syntax
2. The various flavours of function declaration.
3. Passing functions around and how to use passed in functions.
I recommend Jeremy Keith's books: DOM Scripting and Bulletproof Ajax. After you become more fluent in JS I would recommend a JS library(I use jQuery, but that is not important).
JS is important to learn. You cannot use a framework without the proper understanding of how it works. That is doing things backwards.
i thing you should have a good knoloedge base of language specification and DOM (Document Object Model). it means,you shoud know how find/create "page object" an edit properties. Also you should have an idea of "object oriented" javascript tecniques, which the starting point of a lot of framework. you don't need learn specific framework if you don't use it. simple keep in mind generic base concept!
I'll go with the opposite answer most are putting out there. Learning javascript as a developer these days is almost pointless. The language is similar enough to java/C# that it's syntax and semantics shouldn't be lost on you.
What you should learn is jQuery.
As you use jQuery you'll pick up the most common things you'll ever need from javascript anyway.
If you're involved with the Web in anyway then the answer is "Yes, always". Maybe an embedded or system's programmer could get by without JavaScript, but not a webdev.
Most of the libraries are designed to alleviate some of the pain of interacting with a multitude of browsers. They will not abstract away core JavaScript functionality.
Yes, you should learn JavaScript. Sooner or later you will need to use it!