This has friendly/easy tutorials

&lt;a href=&quot;http://developer.mozilla.org/en/Canvas_tutorial&quot;&gt;http://developer.mozilla.org/en/Canvas_tutorial&lt;/a&gt;

This is pretty comprehensive

&lt;a href=&quot;http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#the-canvas-element&quot;&gt;http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#the-canvas-element&lt;/a&gt;

Here is a [HTML5 Canvas cheat sheet][1] (PNG and PDF) and a [HTML version][2] of the same.


Here is a [website dedicated to cheat sheets][3] for developers, but it doesn&#39;t have any other canvas cheat sheets/references.


  [1]: http://blog.nihilogic.dk/2009/02/html5-canvas-cheat-sheet.html
  [2]: http://simon.html5.org/dump/html5-canvas-cheat-sheet.html
  [3]: http://devcheatsheet.com/

I run a site called [Canvas Demos][1], where you can find lots of tutorials and tools to help you build great applications with the canvas element.

It also contains a list of games and applications made by other people with the Canvas element.

  [1]: http://www.canvasdemos.com

Rob Hawkes recently release &quot;Foundation HTML5 Canvas for Games and Entertainment&quot; book.  http://rawkes.com/foundationcanvas

There&#39;s one which covers all the properties/functions:

[A comprehensive reference for HTML5 canvas][1]


  [1]: http://www.rgraph.net/reference

Take a look at the Canvas chapter from **Dive Into HTML5**: [http://diveintohtml5.info/canvas.html][1]


  [1]: http://diveintohtml5.info/canvas.html

I started to program in Scala recently. I&#39;m looking for a free Scala profiler. Reading from the language&#39;s official site led me to [YourKit][1], but the program was not a free one.

Googling &quot;scala profiler&quot; didnt give me any relevant result.

So how do I profile my program written in Scala? I prefer a graphical plugin for Netbeans or Eclipse. But if there is no such thing, then a console one will be fine.

Thanks :)


  [1]: http://www.yourkit.com/

Scala profiler?

I&#39;m trying to compare a character array against a string like so:

    const char *var1 = &quot; &quot;;
    var1 = getenv(&quot;myEnvVar&quot;);
    
    if(var1 == &quot;dev&quot;)
    {
       // do stuff
    }

This if statement never validates as true... when I output var1 it is &quot;dev&quot;, I was thinking maybe it has something to do with a null terminated string, but the strlen of &quot;dev&quot; and var1 are equal... I also thought maybe var1 == &quot;dev&quot; was comparing &quot;dev&quot; against the memory location of var1 instead of the value. *var1 == &quot;dev&quot; results in an error.... tried many things, probably a simple solution for the saavy c++ developer (I havent coded c++ in a looong time).


edit:
we&#39;ve tried

    if(strcmp(var1, &quot;dev&quot;) == 0)

and 

    if(strncmp(var1, &quot;dev&quot;, 3) == 0)


Thanks


edit: After testing at home I&#39;m just going to suggest my co-worker changes the datatype to a string. I believe he was comparing a char array of a large size against a string. I put together a program that outputs sizeof, strlen, etc to help us work through it. Thanks to everyone for the help.


C++ Compare char array with string

Can somebody please refer me to a &lt;strong&gt;comprehensive&lt;/strong&gt; tutorial on Canvas which covers all properties / functions?

I also need a definite reference on Canvas - something like w3schools

Canvas Tutorial / Reference

Can somebody please refer me to a comprehensive tutorial on Canvas which covers all properties / functions?
I also need a definite reference on Canvas - something like w3schools

I can get `window.document` but how can I get `document.window`? I need to know how to do this in all browsers.

How do I get the Window object from the Document object?

I read that when you don&#39;t have access to the web server&#39;s headers you can turn off the cache using:

    &lt;meta http-equiv=&quot;Cache-Control&quot; content=&quot;no-store&quot; /&gt;

But I also read that this doesn&#39;t work in some versions of IE.  Are there any set of &amp;lt;meta&amp;gt; tags that will turn off cache in all browsers?



Is there a &lt;meta&gt; tag to turn off caching in all browsers?

Why is `&lt;form enctype=multipart/form-data&gt;` required when uploading a file to a web-server?

Why is form enctype=multipart/form-data required when uploading a file?

I want to author an anchor tag that executes some JavaScript and then proceeds to go wherever the `href` was taking it. Invoking a function that executes my JavaScript and then sets `window.location` or `top.location` to the `href` location doesn&#39;t work for me.

So, imagine I have an element with id &quot;Foo&quot; on the page. I want to author an anchor similar to:

    &lt;a href=&quot;#Foo&quot; onclick=&quot;runMyFunction(); return false;&quot;&gt;Do it!&lt;/a&gt;

When this is clicked, I want to execute runMyFunction and then jump the page to `#Foo` (not cause a reload - using `top.location` would cause it to reload the page).

Suggestions? I am happy to use jQuery if it can help here...

HTML anchor link - href and onclick both?

Does anyone know of an extension for Firefox, or a script or some other mechanism, that can monitor one or more local files. Firefox would auto-refresh or otherwise update its canvas when it detected a change (of timestamp) in the files(s).

For editing CSS, it would be ideal if just the CSS could be reloaded, rather than a full HTML re-render.

Effectively it would enable similar behaviour to Firebug with its dynamic HTML/CSS editing, only through external files.

How do I make Firefox auto-refresh on file change?

After experimenting with composite operations and drawing images on the canvas I&#39;m now trying to remove images and compositing. How do I do this?

I need to clear the canvas for redrawing other images; this can go on for a while so I don&#39;t think drawing a new rectangle every time will be the most efficient option.

How to clear the canvas for redrawing

There doesnt seem to be a native function to draw an oval-like shape. Also i am not looking for the egg-shape.

Is it possible to draw an oval with 2 bezier curves?
Somebody expierenced with that?

My purpose is to draw some eyes and actually im just using arcs.
Thanks in advance.

**Solution**

So scale() changes the scaling for all next shapes.
Save() saves the settings before and restore is used to restore the settings to draw new shapes without scaling.

Thanks to Jani

    ctx.save();
    ctx.scale(0.75, 1);
    ctx.beginPath();
    ctx.arc(20, 21, 10, 0, Math.PI*2, false);
    ctx.stroke();
    ctx.closePath();
    ctx.restore();

How to draw an oval in html5 canvas?

I&#39;m trying to create a thumbnail image on the client side using javascript and a canvas element, but when I shrink the image down, it looks terrible.  It looks as if it was downsized in photoshop with the resampling set to &#39;Nearest Neighbor&#39; instead of Bicubic.  I know its possible to get this to look right, because [this site][1] can do it just fine using a canvas as well.  I&#39;ve tried using the same code they do as shown in the &quot;[Source]&quot; link, but it still looks terrible.  Is there something I&#39;m missing, some setting that needs to be set or something?

EDIT:

I&#39;m trying to resize a jpg.  I have tried resizing the same jpg on the linked site and in photoshop, and it looks fine when downsized.

Here is the relevant code:

    reader.onloadend = function(e)
	{
		var img = new Image();
		var ctx = canvas.getContext(&quot;2d&quot;);
		var canvasCopy = document.createElement(&quot;canvas&quot;);
		var copyContext = canvasCopy.getContext(&quot;2d&quot;);
		
		img.onload = function()
		{
			var ratio = 1;
			
			if(img.width &gt; maxWidth)
				ratio = maxWidth / img.width;
			else if(img.height &gt; maxHeight)
				ratio = maxHeight / img.height;
				
			canvasCopy.width = img.width;
			canvasCopy.height = img.height;
			copyContext.drawImage(img, 0, 0);
				
			canvas.width = img.width * ratio;
			canvas.height = img.height * ratio;
			ctx.drawImage(canvasCopy, 0, 0, canvasCopy.width, canvasCopy.height, 0, 0, canvas.width, canvas.height);
		};

		img.src = reader.result;
	}

EDIT2:

Seems I was mistaken, the linked website wasn&#39;t doing any better of a job of downsizing the image.  I tried the other methods suggested and none of them look any better.  This is what the different methods resulted in:

Photoshop:

![alt text][2]

Canvas:

![alt text][3]

Image with image-rendering: optimizeQuality set and scaled with width/height:

![alt text][4]

Image with image-rendering: optimizeQuality set and scaled with -moz-transform:

![alt text][5]

Canvas resize on pixastic:

![alt text][6]

I guess this means firefox isn&#39;t using bicubic sampling like its supposed to.  I&#39;ll just have to wait until they actually add it.

EDIT3:

[Original Image][7]


  [1]: http://www.rigasa.ch/~labo/labo/pixastic/editor/
  [2]: http://i.stack.imgur.com/K6ztq.png
  [3]: http://i.stack.imgur.com/nD3FJ.png
  [4]: http://i.stack.imgur.com/I6RkV.png
  [5]: http://i.stack.imgur.com/ZWiVC.png
  [6]: http://i.stack.imgur.com/PEsYM.png
  [7]: http://i.stack.imgur.com/5x1UP.jpg

Resizing an image in an HTML5 canvas

Using the HTML5 `&lt;canvas&gt;` element, I would like to load an image file (PNG, JPEG, etc.), draw it to the canvas completely transparently, and then fade it in. I have figured out how to load the image and draw it to the canvas, but I don&#39;t know how to change its opacity.

Here&#39;s the code I have so far:

    var canvas = document.getElementById(&#39;myCanvas&#39;);
    	
    if (canvas.getContext)
    {
    	var c			= canvas.getContext(&#39;2d&#39;);
    	c.globalAlpha	= 0;
    	
    	var img		= new Image();
    	img.onload	= function() {
    		c.drawImage(img, 0, 0);
    	}
    	img.src		= &#39;image.jpg&#39;;
    }

Will somebody please point me in the right direction like a property to set or a function to call that will change the opacity?

How to change the opacity (alpha, transparency) of an element in a canvas element?

I want to draw on a HTML Canvas using a mouse (for example, draw a signature, draw a name, ...)

How would I go about implementing this?

Content Type	Original Author	Original Content on Stackoverflow
Question	KJ Saxena	View Question on Stackoverflow
Solution 1 - Html	Jacob	View Answer on Stackoverflow
Solution 2 - Html	David Johnstone	View Answer on Stackoverflow
Solution 3 - Html	Andi Smith	View Answer on Stackoverflow
Solution 4 - Html	Seth Ladd	View Answer on Stackoverflow
Solution 5 - Html	Richard	View Answer on Stackoverflow
Solution 6 - Html	Ghigo	View Answer on Stackoverflow

Canvas Tutorial / Reference

Html Problem Overview

Html Solutions

Solution 1 - Html

Solution 2 - Html

Solution 3 - Html

Solution 4 - Html

Solution 5 - Html

Solution 6 - Html

C++ Compare char array with string

Scala profiler?

Attributions