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  • Create a Color Picker, similar to Photoshop's, using Javascript and HTML Canvas

    - by André Alçada Padez
    I am not at all versed in Computer Graphics and am in need of creating a color picker as a javascript tool to embed in an HTML page. First, and looking at Photoshop's one, i thought of the RGB palette as a three-dimensional matrix. My first attempt envolved: <script type="text/javascript"> var rgCanvas = document.createElement('canvas'); rgCanvas.width = 256; rgCanvas.height = 256; rgCanvas.style.border = '3px solid black'; for (g = 0; g < 256; g++){ for (r = 0; r < 256; r++){ var context = rgCanvas.getContext('2d'); context.beginPath(); context.moveTo(r,g); context.strokeStyle = 'rgb(' + r + ', ' + g + ', 0)'; context.lineTo(r+1,g+1); context.stroke(); context.closePath(); } } var bCanvas = document.createElement('canvas'); bCanvas.width = 20; bCanvas.height = 256; bCanvas.style.border = '3px solid black'; for (b = 0; b < 256; b++){ var context = bCanvas.getContext('2d'); context.beginPath(); context.moveTo(0,b); context.strokeStyle = 'rgb(' + 0 + ', ' + 0 + ', ' + b + ')'; context.lineTo(20, b); context.stroke(); context.closePath(); } document.body.appendChild(rgCanvas); document.body.appendChild(bCanvas); </script> this results in something like My thought is this is too linear, comparing to the ones i see in Photoshop and on the web. I would like to know the logic behind the color mapping in a picker like this: I don't really need the algorythms itself, i'm mainly trying to understand the logic. Thanks

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  • Flash animations with Javascript?

    - by RichardBlizzard
    Hi all, How does something like this work without Flash? http://www.dirtyphonebook.com/dashboard/425-205-1921 I right-clicked on it but there's no Flash menu. I love Flash because its stable and works. But is using some sort of Javascript hack for this kind of complex behavior actually a good idea?

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  • Eclipse outline of Prototype javascript classes

    - by Rob Agar
    Is there a way to show the structure of a javascript class declared using Prototype's Class.create function in the Eclipse outline view? The declarations look like: var Foo = Class.create({ bar: function() { ... }, baz: function() { ... }, }); At the moment all I get is "Foo:". (A google search turned up http://marketplace.eclipse.org/content/prototypewtp, but the link to the plugin homepage is dead)

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  • Javascript:history.back is not workin in XUL application

    - by Rajeesh
    I have created a XUL application, it has got a link for navigating to previous page. This is my link <a href="javascript:history.back();">Back</a>, unfortunately it is not working!!! In firefox is working as expected, when I run it in XUL it is not working. Any idea, why it is not working. Thanks, Rajeesh

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  • Dreamweaver javascript code hints

    - by xdevel2000
    I'd to use DW cs 4 but before to buy I want to test javascript code hints. However that feature doesn't work at all. I have an external .js library and then into an html file I load it but when I type functions or object by name nothing happen. Any idea?

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  • mvc external javascript referencing problem

    - by user281180
    I recently asked this question but to my suprise, it worked fine for some time and now has stopped again! I have a javascript in my script and I have added the link in my view as follows: It has certain functions which I can access once I have the script in my view. But when running I can see that the fucntions are not called instead i`m getting the error message Object expected at line 104. Why am I having this error and how can I solve it?

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  • Javascript Mp3 Player, NONE FLASH

    - by Yo Momma
    I currently have a simple flash Mp3 player on my site which works lovely. The issue is, most cell phones do not support flash and a large portion of my visitors come through via a mobile device. The alternative to this is to replace the flash player with a javascript player. I found a JQuery one but it only works on HTML5 compatible browsers. Does anyone know of a good alternative that would work on mobile devices as well as most desktop web browsers?

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  • javascript undefined compare

    - by nahum
    Ok here is my question in javascript you can declare a variable and be undefined you can apply variable == undefined, I know that but how you can compare a value that you dont know yet if it's in the cpu memory. I have a class which is create it when the user click on a button. before this the class is undefined there no exist in any where so how can I compare it? without using try{}catch(e){} is there a way????

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  • round number in JavaScript to N decimal places

    - by Richard
    in JavaScript, the typical way to round a number to N decimal places is something like: function round_number(num, dec) { return Math.round(num * Math.pow(10, dec)) / Math.pow(10, dec); } However this approach will round to a maximum of N decimal places while I want to always round to N decimal places. For example "2.0" would be rounded to "2". Any ideas?

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  • Javascript VS C#

    - by Joris
    Maybe a strange and green question, but Is there anything C# can't do what javascript can... And considering JQuery? except for the fact that one is clientside, and the other serverside? Or am I asking a very stupid question now?

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  • Javascript/jQuery HasLoaded or equivalent?

    - by maxp
    I know in jquery it is possible to call the javascript/jquery onload()/load() functions on, for example an image (<img>). However, if in jquery if i use .html(htmlString) to insert an image after the dom has loaded, how can i add a listener to handle the images onload event? Is there a property I can check to see various images and if they have loaded?

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  • Does this incorporate JavaScript closures?

    - by alex
    In trying to learn JavaScript closures, I've confused myself a bit. From what I've gathered over the web, a closure is... Declaring a function within another function, and that inner function has access to its parent function's variables, even after that parent function has returned. Here is a small sample of script from a recent project. It allows text in a div to be scrolled up and down by buttons. var pageScroll = (function() { var $page, $next, $prev, canScroll = true, textHeight, scrollHeight; var init = function() { $page = $('#secondary-page'); // reset text $page.scrollTop(0); textHeight = $page.outerHeight(); scrollHeight = $page.attr('scrollHeight'); if (textHeight === scrollHeight) { // not enough text to scroll return false; }; $page.after('<div id="page-controls"><button id="page-prev">prev</button><button id="page-next">next</button></div>'); $next = $('#page-next'); $prev = $('#page-prev'); $prev.hide(); $next.click(scrollDown); $prev.click(scrollUp); }; var scrollDown = function() { if ( ! canScroll) return; canScroll = false; var scrollTop = $page.scrollTop(); $prev.fadeIn(500); if (scrollTop == textHeight) { // can we scroll any lower? $next.fadeOut(500); } $page.animate({ scrollTop: '+=' + textHeight + 'px'}, 500, function() { canScroll = true; }); }; var scrollUp = function() { $next.fadeIn(500); $prev.fadeOut(500); $page.animate({ scrollTop: 0}, 500); }; $(document).ready(init); }()); Does this example use closures? I know it has functions within functions, but is there a case where the outer variables being preserved is being used? Am I using them without knowing it? Thanks Update Would this make a closure if I placed this beneath the $(document).ready(init); statement? return { scrollDown: scrollDown }; Could it then be, if I wanted to make the text scroll down from anywhere else in JavaScript, I could do pageScroll.scrollDown(); I'm going to have a play around on http://www.jsbin.com and report back

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