javascript - Limit canvas colors to a specific array -


how can limit rgb color space of canvas image specific array of colors? f.ex:

var colors = ['#aaffee','#cc44cc','#00cc55','#0000aa']; var rgb = [230,111,90];  // match rgb colors , return closest match

i need closest match array when loop through pixels in canvas image data. there clever function can that?

how limit colors specific color palette

you must map each , every original pixel nearest palette color.

to calculate distance between original , palette colors on colorwheel.

here illustration. original pixel (orange color) has arrows each color in our specified palette (assume our palette has 3 specified colors: red, green, blue).

the palette color shortest arrow length substituted original pixel.

since orange-red arrow shortest, palette red substituted original orange.

enter image description here

this important function maps original color palette color:

    // use euclidian distance find closest color     // send in rgb of pixel substituted     function mapcolortopalette(red,green,blue){         var color,diffr,diffg,diffb,diffdistance,mappedcolor;         var distance=25000;         for(var i=0;i<palette.length;i++){             color=palette[i];             diffr=( color.r - red );             diffg=( color.g - green );             diffb=( color.b - blue );             diffdistance = diffr*diffr + diffg*diffg + diffb*diffb;             if( diffdistance < distance  ){                  distance=diffdistance;                  mappedcolor=palette[i];              };         }         return(mappedcolor);     }

here code , fiddle: http://jsfiddle.net/m1erickson/gwqqh/

note: can improve code using hash tables, tree searches, etc.

<!doctype html> <html> <head> <link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css --> <script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>  <style>     body{ background-color: ivory; padding:15px; }     canvas{border:1px solid red;} </style>  <script> $(function(){      var canvasoriginal=document.getelementbyid("originalcanvas");     var ctx=canvasoriginal.getcontext("2d");     var canvasmapped=document.getelementbyid("mappedcanvas");     var ctxmapped=canvasmapped.getcontext("2d");      // draw off-colored rectangles     ctx.beginpath();     ctx.fillstyle="rgb(140,70,60)"; //red-ish     ctx.rect(10,10,20,20);     ctx.fill();     ctx.beginpath();     ctx.fillstyle="rgb(70,140,60)";  //green-ish     ctx.rect(10,40,20,20);     ctx.fill();     ctx.beginpath();     ctx.fillstyle="rgb(70,60,140)";  //blue-ish     ctx.rect(10,70,20,20);     ctx.fill();      // create array of palette colors     var palette=[{r:255,g:0,b:0},{r:0,g:255,b:0},{r:0,g:0,b:255}];      // load pixels array     var imagedata=ctx.getimagedata(0,0,canvasoriginal.width,canvasoriginal.height);     var data=imagedata.data;      // rewrite pixels using mapped colors     var mappedcolor;     for(var i=0; i<data.length; i+=4) {       mappedcolor = mapcolortopalette(data[i], data[i+1], data[i+2]);       if(data[i+3]>10){           data[i]   = mappedcolor.r;           data[i+1] = mappedcolor.g;           data[i+2] = mappedcolor.b;       }     }         ctxmapped.putimagedata(imagedata,0,0);      // use euclidian distance find closest color     function mapcolortopalette(red,green,blue){         var color,diffr,diffg,diffb,diffdistance,mappedcolor;         var distance=25000;         for(var i=0;i<palette.length;i++){             color=palette[i];             diffr=( color.r - red );             diffg=( color.g - green );             diffb=( color.b - blue );             diffdistance = diffr*diffr + diffg*diffg + diffb*diffb;             if( diffdistance < distance  ){                  distance=diffdistance;                  mappedcolor=palette[i];              };         }         return(mappedcolor);     }   }); // end $(function(){}); </script>  </head>  <body>     <canvas id="originalcanvas" width=60 height=100></canvas>     <canvas id="mappedcanvas" width=60 height=100></canvas> </body> </html>

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