[CamanJS][1] is the most flexible non-interactive (API, not point-and-click) JavaScript library for image manipulation, that I came across so far.


  [1]: http://camanjs.com/

Try to look to the [Processing.js library][1].
This is a quotation from theirs site:

&gt; Processing.js is the sister project of
&gt; the popular Processing visual
&gt; programming language, designed for the
&gt; web.

As far as I know it has more contributors than Pixastic project does and theirs [demos][2] are really promising.

  [1]: http://processingjs.org/
  [2]: http://processingjs.org/exhibition

Take a look at [Pixastic][1]

&gt; Pixastic is an experimental library which allows you to perform a variety of operations on images using just a bit of JavaScript. The effects supported out of the box include desaturation/greyscale, invert, flipping, brightness/contrast adjustment, hue/saturation, emboss, blur, and many more.

Demo can be found [here][2]


  [1]: http://www.pixastic.com/lib/
  [2]: http://editor.pixastic.com/

have a look at the [PSX][1] imageprocessing library, it contains a javascript and ios version.
the [demo site][2] shows what it can do.
PSX is the most powerful javascript image processing library ever.



  [1]: https://github.com/zhijie/psx
  [2]: http://toys.lzhj.me/psx/

Sometimes it makes sense to cluster related data together.  I tend to do so with a dict, e.g.,

    self.group = dict(a=1, b=2, c=3)
    print self.group[&#39;a&#39;]

One of my colleagues prefers to create a class

    class groupClass(object):
        def __init__(a, b, c):
            self.a = a
            self.b = b
            self.c = c
    self.group = groupClass(1, 2, 3)
    print self.group.a

Note that we are not defining any class methods.

I like to use a dict because I like to minimize the number of lines of code.  My colleague thinks the code is more readable if you use a class, and it makes it easier to add methods to the class in the future.

Which do you prefer and why?



Using Python class as a data container

How do I calculate the intersection points of two circles.  I would expect there to be either two, one or no intersection points in all cases.

I have the x and y coordinates of the centre-point, and the radius for each circle.

An answer in python would be preferred, but any working algorithm would be acceptable.

Circle-circle intersection points

I need some kick-ass effects for my web site, like gaussian blur, noise, convolution filters, morphological operations etc.
All effects must be applied dynamically (no pre-renderend images) and being changed over time.

What is the most powerful image processing library, implemented in JavaScript ?

What is the best JavaScript image processing library?

<p>I need some kick-ass effects for my web site, like gaussian blur, noise, convolution filters, morphological operations etc.
All effects must be applied dynamically (no pre-renderend images) and being changed over time.</p>
<p>What is the most powerful image processing library, implemented in JavaScript ?</p>


How can I declare a global variable in JavaScript?



How to declare a global variable in JavaScript

How can we use PHP code in JavaScript?

Like

    function jst()
    {
        var i = 0;
        i = &lt;?php echo 35; ?&gt;
        alert(i);
    }

Please suggest a better way.


How do I embed PHP code in JavaScript?

If I didn&#39;t need localStorage, my code would look like this:

    var names=new Array(); 
    names[0]=prompt(&quot;New member name?&quot;);

This works. However, I need to store this variable in localStorage and it&#39;s proving quite stubborn. I&#39;ve tried:

    var localStorage[names] = new Array();
    localStorage.names[0] = prompt(&quot;New member name?&quot;);

Where am I going wrong?


How do I store an array in localStorage?

&gt; **Possible Duplicates:**  
&gt; [Why would a javascript variable start with a dollar sign?](https://stackoverflow.com/questions/205853/why-would-a-javascript-variable-start-with-a-dollar-sign)  
&gt; [JQuery : What is the difference between &amp;ldquo;var test&amp;rdquo; and &amp;ldquo;var $test&amp;rdquo;](https://stackoverflow.com/questions/2880926/jquery-what-is-the-difference-between-var-test-and-var-test)  

&lt;!-- End of automatically inserted text --&gt;

What is the difference between this two ways of initializing variables?

    var $val = &#39;something&#39;
    
         OR
    
    var val = &#39;something&#39;

as I see they are the same thing.

Maybe in this case `$` is only the part of name in variable?
(it will become a meaningless question in that case:/)

Thanks

Why use $ (dollar sign) in the name of javascript variables?

How could I generalise the function below to take N arguments?  (Using call or apply?)

Is there a programmatic way to apply arguments to &#39;new&#39;? I don&#39;t want the constructor to be treated like a plain function.

    /**
     * This higher level function takes a constructor and arguments
     * and returns a function, which when called will return the 
     * lazily constructed value.
     * 
     * All the arguments, except the first are pased to the constructor.
     * 
     * @param {Function} constructor
     */ 

    function conthunktor(Constructor) {
    	var args = Array.prototype.slice.call(arguments, 1);
    	return function() {
    		console.log(args);
    		if (args.length === 0) {
    			return new Constructor();
    		}
    		if (args.length === 1) {
    			return new Constructor(args[0]);
    		}
    		if (args.length === 2) {
    			return new Constructor(args[0], args[1]);
    		}
    		if (args.length === 3) {
    			return new Constructor(args[0], args[1], args[2]);
    		}
    		throw(&quot;too many arguments&quot;);    
    	}
    }


qUnit test:
    
    test(&quot;conthunktorTest&quot;, function() {
    	function MyConstructor(arg0, arg1) {
    		this.arg0 = arg0;
    		this.arg1 = arg1;
    	}
    	MyConstructor.prototype.toString = function() {
    		return this.arg0 + &quot; &quot; + this.arg1;
    	}
    	
    	var thunk = conthunktor(MyConstructor, &quot;hello&quot;, &quot;world&quot;);
    	var my_object = thunk();
    	deepEqual(my_object.toString(), &quot;hello world&quot;);
    });

How can I call a javascript constructor using call or apply?

I am new to this site, and I come with a question about Android.


Is there any way to convert a Bitmap to grayscale? I know how to draw a grayscale bitmap (using canvas operations: http://www.mail-archive.com/android-developers@googlegroups.com/msg38890.html) but I really need The actual bitmap in gray colors (or at least something that could be converted to a bitmap later on).
Do I have to implement it by hand (pixel by pixel operations)?

I&#39;ve searched a lot, and still could not find. Anyone knows a easy/efficient way to do it?

Thanks a lot!

Convert a Bitmap to GrayScale in Android

I&#39;m helping a veterinary clinic measuring pressure under a dogs paw. I use Python for my data analysis and now I&#39;m stuck trying to divide the paws into (anatomical) subregions.

I made a 2D array of each paw, that consists of the maximal values for each sensor that has been loaded by the paw over time. Here&#39;s an example of one paw, where I used Excel to draw the areas I want to &#39;detect&#39;. These are 2 by 2 boxes around the sensor with local maxima&#39;s, that together have the largest sum.

![alt text][1]

So I tried some experimenting and decide to simply look for the maximums of each column and row (can&#39;t look in one direction due to the shape of the paw). This seems to &#39;detect&#39; the location of the separate toes fairly well, but it also marks neighboring sensors. 


![alt text][2]

So what would be the best way to tell Python which of these maximums are the ones I want? 

**Note: The 2x2 squares can&#39;t overlap, since they have to be separate toes!**

Also I took 2x2 as a convenience, any more advanced solution is welcome, but I&#39;m simply a human movement scientist, so I&#39;m neither a real programmer or a mathematician, so please keep it &#39;simple&#39;. 

Here&#39;s a [version that can be loaded with `np.loadtxt`](https://upl.io/0liy07)


----------

Results
-------

So I tried @jextee&#39;s solution (see the results below). As you can see, it works very on the front paws, but it works less well for the hind legs. 

More specifically, it can&#39;t recognize the small peak that&#39;s the fourth toe. This is obviously inherent to the fact that the loop looks top down towards the lowest value, without taking into account where this is. 

Would anyone know how to tweak @jextee&#39;s algorithm, so that it might be able to find the 4th toe too?

![alt text][3]

Since I haven&#39;t processed any other trials yet, I can&#39;t supply any other samples. But the data I gave before were the averages of each paw. This file is an array with the maximal data of 9 paws in the order they made contact with the plate.

This image shows how they were spatially spread out over the plate.

![alt text][4]

Update:
-------

**[I have set up a blog for anyone interested](http://www.flipserd.com/blog/ivoflipse/post/toe-detection-revisited)** and [I have setup a OneDrive with all the raw measurements.][5] So to anyone requesting more data: more power to you! 

----------

New update:
-----------

So after the help I got with my questions regarding [paw detection][6] and [paw sorting][7], I was finally able to check the toe detection for every paw! Turns out, it doesn&#39;t work so well in anything but paws sized like the one in my own example. Off course in hindsight, it&#39;s my own fault for choosing the 2x2 so arbitrarily.

Here&#39;s a nice example of where it goes wrong: a nail is being recognized as a toe and the &#39;heel&#39; is so wide, it gets recognized twice!

![alt text][8]

The paw is too large, so taking a 2x2 size with no overlap, causes some toes to be detected twice. The other way around, in small dogs it often fails to find a 5th toe, which I suspect is being caused by the 2x2 area being too large.

After [trying the current solution on all my measurements][9] I came to the staggering conclusion that for nearly all my small dogs it didn&#39;t find a 5th toe and that in over 50% of the impacts for the large dogs it would find more!

So clearly I need to change it. My own guess was changing the size of the `neighborhood` to something smaller for small dogs and larger for large dogs. But `generate_binary_structure` wouldn&#39;t let me change the size of the array. 

Therefore, I&#39;m hoping that anyone else has a better suggestion for locating the toes, perhaps having the toe area scale with the paw size?


  [1]: http://i.stack.imgur.com/BuUbq.png
  [2]: http://i.stack.imgur.com/UyNRU.png
  [3]: http://i.stack.imgur.com/FFX0x.png
  [4]: http://i.stack.imgur.com/iPXEv.png
  [5]: https://1drv.ms/u/s!AjVZ_ROiXWgOhDEn4KrRB8mrOZWM?e=aUCCm4
  [6]: https://stackoverflow.com/q/4087919/77595
  [7]: https://stackoverflow.com/q/4502656/77595
  [8]: http://i.stack.imgur.com/JEpIa.png
  [9]: http://www.flipserd.com/blog/ivoflipse/post/toe-detection-revisited

Peak detection in a 2D array

After my previous question on [finding toes within each paw][1], I started loading up other measurements to see how it would hold up. Unfortunately, I quickly ran into a problem with one of the preceding steps: recognizing the paws.

You see, my proof of concept basically took the maximal pressure of each sensor over time and would start looking for the sum of each row, until it finds on that != 0.0. Then it does the same for the columns and as soon as it finds more than 2 rows with that are zero again. It stores the minimal and maximal row and column values to some index.

![alt text][2]

As you can see in the figure, this works quite well in most cases. However, there are a lot of downsides to this approach (other than being very primitive):

- Humans can have &#39;hollow feet&#39; which means there are several empty rows within the footprint itself. Since I feared this could happen with (large) dogs too, I waited for at least 2 or 3 empty rows before cutting off the paw. 
  
  This creates a problem if another contact made in a different column before it reaches several empty rows, thus expanding the area. I figure I could compare the columns and see if they exceed a certain value, they must be separate paws.

- The problem gets worse when the dog is very small or walks at a higher pace. What happens is that the front paw&#39;s toes are still making contact, while the hind paw&#39;s toes just start to make contact within the same area as the front paw!

  With my simple script, it won&#39;t be able to split these two, because it would have to determine which frames of that area belong to which paw, while currently I would only have to look at the maximal values over all frames.

Examples of where it starts going wrong:

![alt text][3]
![alt text][4]

**So now I&#39;m looking for a better way of recognizing and separating the paws** (after which I&#39;ll get to the problem of deciding which paw it is!).

**Update:**

I&#39;ve been tinkering to get Joe&#39;s (awesome!) answer implemented, but I&#39;m having difficulties extracting the actual paw data from my files.

![alt text][5]

The coded_paws shows me all the different paws, when applied to the maximal pressure image (see above). However, the solution goes over each frame (to separate overlapping paws) and sets the four Rectangle attributes, such as coordinates or height/width. 

I can&#39;t figure out how to take these attributes and store them in some variable that I can apply to the measurement data. Since I need to know for each paw, what its location is during which frames and couple this to which paw it is (front/hind, left/right).

**So how can I use the Rectangles attributes to extract these values for each paw?**

I have the measurements I used in the question setup in my public Dropbox folder ([example 1][6], [example 2][7], [example 3][8]). [For anyone interested I also set up a blog][9] to keep you up to date :-)

  [1]: https://stackoverflow.com/questions/3684484
  [2]: http://i.stack.imgur.com/j6eWv.png
  [3]: http://i.stack.imgur.com/kPTj3.png
  [4]: http://i.stack.imgur.com/xKLOq.png
  [5]: http://i.stack.imgur.com/83Xx5.png
  [6]: http://dl.dropbox.com/u/5207386/Examples/Normal%20measurement
  [7]: http://dl.dropbox.com/u/5207386/Examples/Grouped%20up%20paws
  [8]: http://dl.dropbox.com/u/5207386/Examples/Overlapping%20paws
  [9]: http://flipserd.com/blog


How can I improve my paw detection?

I want to use OpenCV2.0 and Python2.6 to show resized images. I used and adopted [this][1] example but unfortunately, this code is for OpenCV2.1 and does not seem to be working on 2.0. Here my code:

    import os, glob
    import cv

    ulpath = &quot;exampleshq/&quot;

    for infile in glob.glob( os.path.join(ulpath, &quot;*.jpg&quot;) ):
        im = cv.LoadImage(infile)
        thumbnail = cv.CreateMat(im.rows/10, im.cols/10, cv.CV_8UC3)
        cv.Resize(im, thumbnail)
        cv.NamedWindow(infile)
        cv.ShowImage(infile, thumbnail)
        cv.WaitKey(0)
        cv.DestroyWindow(name)

Since I cannot use

    cv.LoadImageM

I used 

    cv.LoadImage

instead, which was no problem in other applications. Nevertheless, cv.iplimage has no attribute rows, cols or size. Can anyone give me a hint, how to solve this problem?


  [1]: http://opencv.willowgarage.com/documentation/python/cookbook.html

How to resize an image with OpenCV2.0 and Python2.6

I need a simple and fast way to compare two images for similarity. I.e. I want to get a high value if they contain exactly the same thing but may have some slightly different background and may be moved / resized by a few pixel.

(More concrete, if that matters: The one picture is an icon and the other picture is a subarea of a screenshot and I want to know if that subarea is exactly the icon or not.)

I have **OpenCV** at hand but I am still not that used to it.

One possibility I thought about so far: Divide both pictures into 10x10 cells and for each of those 100 cells, compare the color histogram. Then I can set some made up threshold value and if the value I get is above that threshold, I assume that they are similar.

I haven&#39;t tried it yet how well that works but I guess it would be good enough. The images are already pretty much similar (in my use case), so I can use a pretty high threshold value.

I guess there are dozens of other possible solutions for this which would work more or less (as the task itself is quite simple as I only want to detect similarity if they are really very similar). What would you suggest?

---

There are a few very related / similar questions about obtaining a signature/fingerprint/hash from an image:

* [OpenCV / SURF How to generate a image hash / fingerprint / signature out of the descriptors?](https://stackoverflow.com/questions/2146542/opencv-surf-how-to-generate-a-image-hash-fingerprint-signature-out-of-the)
* [Image fingerprint to compare similarity of many images](https://stackoverflow.com/questions/596262/image-fingerprint-to-compare-similarity-of-many-images)
* [Near-Duplicate Image Detection](https://stackoverflow.com/questions/1034900/near-duplicate-image-detection/)
* [OpenCV: Fingerprint Image and Compare Against Database](https://stackoverflow.com/questions/7205489/opencv-fingerprint-image-and-compare-against-database).
* [more](https://stackoverflow.com/questions/843972/image-comparison-fast-algorithm), [more](https://stackoverflow.com/questions/23931/algorithm-to-compare-two-images), [more](https://stackoverflow.com/questions/189943/how-can-i-quantify-difference-between-two-images), [more](https://stackoverflow.com/questions/25977/how-can-i-measure-the-similarity-between-two-images), [more](https://stackoverflow.com/questions/75891/algorithm-for-finding-similar-images), [more](https://stackoverflow.com/questions/5730631/image-similarity-comparison), [more](https://stackoverflow.com/questions/25105599/algorithm-for-finding-similar-images-using-an-index)

Also, I stumbled upon these implementations which have such functions to obtain a fingerprint:

* [pHash](http://phash.org/)
* [imgSeek](http://www.imgseek.net/) ([GitHub repo](https://github.com/ricardocabral/iskdaemon)) (GPL) based on the paper [Fast Multiresolution Image Querying](http://grail.cs.washington.edu/projects/query/)
* [image-match](https://github.com/ascribe/image-match). Very similar to what I was searching for. Similar to pHash, based on [An image signature for any kind of image, Goldberg et al](http://www.cs.cmu.edu/~hcwong/Pdfs/icip02.ps). Uses Python and Elasticsearch.
* [iqdb](http://iqdb.org/code/)
* [ImageHash](https://github.com/JohannesBuchner/imagehash). supports pHash.
* [Image Deduplicator (imagededup)](https://idealo.github.io/imagededup/). Supports CNN, PHash, DHash, WHash, AHash.

Some discussions about perceptual image hashes: [here](https://news.ycombinator.com/item?id=2614797)

---

A bit offtopic: There exists many methods to create audio fingerprints. [MusicBrainz](http://musicbrainz.org), a web-service which provides fingerprint-based lookup for songs, has a [good overview in their wiki](http://wiki.musicbrainz.org/Fingerprinting). They are using [AcoustID](http://acoustid.org/) now. This is for finding exact (or mostly exact) matches. For finding similar matches (or if you only have some snippets or high noise), take a look at [Echoprint](http://echoprint.me/). A related SO question is [here](https://stackoverflow.com/questions/2068286/music-recognition-and-signal-processing). So it seems like this is solved for audio. All these solutions work quite good.

A somewhat more generic question about fuzzy search in general is [here](https://stackoverflow.com/questions/13514575/how-to-do-fuzzy-search-in-big-data). E.g. there is [locality-sensitive hashing](http://en.wikipedia.org/wiki/Locality-sensitive_hashing) and [nearest neighbor search](http://en.wikipedia.org/wiki/Nearest_neighbor_search).

Content Type	Original Author	Original Content on Stackoverflow
Question	AntonAL	View Question on Stackoverflow
Solution 1 - Javascript	Leonid Mamchenkov	View Answer on Stackoverflow
Solution 2 - Javascript	Andrey	View Answer on Stackoverflow
Solution 3 - Javascript	SteD	View Answer on Stackoverflow
Solution 4 - Javascript	zhijie	View Answer on Stackoverflow

What is the best JavaScript image processing library?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

Solution 3 - Javascript

Solution 4 - Javascript

Circle-circle intersection points

Using Python class as a data container

Attributions