<div class="container">
    <div class="column1">
        <canvas id="color" width="500" height="128"></canvas>
    </div>
    <div class="column2">
        <div>Предпросмотр:</div>
        <div id="preview"></div>
        <div id="pick"></div>
    </div>
    <div style="clear:both;"></div>
</div>
<canvas id="panel" width="1000" height="600"></canvas>

/* page layout styles */
*{
    margin:0;
    padding:0;
}
body {
    background-color:#eee;
    color:#fff;
    font:14px/1.3 Arial,sans-serif;
}
.container {
    color: #000;
    margin: 20px auto;
    overflow: hidden;
    position: relative;
    width: 800px;
}
 
/* custom styles */
.column1 {
    float:left;
    width:500px;
}
.column2 {
    float:left;
    padding-left:20px;
    width:170px;
}
#panel {
    border:1px #000 solid;
    box-shadow:4px 6px 6px #444444;
    cursor:crosshair;
    display:block;
    margin:0 auto;
    height:600px;
    width:1000px;
}
#color {
    border:1px #000 solid;
    box-shadow:0px 4px 6px #444444;
    cursor:crosshair;
}
.column2 > div {
    margin-bottom:10px;
}
#preview, #pick {
    background-color:rgb(0, 195, 135);
    border:1px #000 solid;
    box-shadow:2px 3px 3px #444444;
    height:40px;
    width:80px;
 
    border-radius:3px;
    -moz-border-radius:3px;
    -webkit-border-radius:3px;
}

var canvas;
var canvasColor;
var ctx;
var ctxColor;
var bMouseDown = false;
var selColorR = 0;
var selColorG = 195;
var selColorB = 135;
 
var BubbleBrush = {
    // inner variables
    iPrevX : 0,
    iPrevY : 0,
 
    // initialization function
    init: function () {
        ctx.globalCompositeOperation = 'source-over'; //'lighter' is nice too
        ctx.lineWidth = 1;
        ctx.strokeStyle = 'rgba(0, 0, 0, 0.2)';
        ctx.lineWidth = 2;
    },
 
    startCurve: function (x, y) {
        this.iPrevX = x;
        this.iPrevY = y;
        ctx.fillStyle = 'rgba(' + selColorR + ', ' + selColorG + ', ' + selColorB + ', 0.9)';
    },
 
    draw: function (x, y) {
        var iXAbs = Math.abs(x - this.iPrevX);
        var iYAbs = Math.abs(y - this.iPrevY);
        iXAbs = (iXAbs > 30) ? 30 : iXAbs;
        iYAbs = (iYAbs > 30) ? 30 : iYAbs;
 
        if (iXAbs > 10 || iYAbs > 10) {
            ctx.beginPath();
            ctx.arc(this.iPrevX, this.iPrevY, (iXAbs + iYAbs) * 0.5, 0, Math.PI*2, false);
            ctx.fill();
            ctx.stroke();
            this.iPrevX = x;
            this.iPrevY = y;
        }
    }
};
 
$(function(){
    // creating canvas objects
    canvas = document.getElementById('panel');
    ctx = canvas.getContext('2d');
 
    canvasColor = document.getElementById('color');
    ctxColor = canvasColor.getContext('2d');
 
    drawGradients(ctxColor);
 
    BubbleBrush.init();
 
    $('#color').mousemove(function(e) { // mouse move handler
        var canvasOffset = $(canvasColor).offset();
        var canvasX = Math.floor(e.pageX - canvasOffset.left);
        var canvasY = Math.floor(e.pageY - canvasOffset.top);
 
        var imageData = ctxColor.getImageData(canvasX, canvasY, 1, 1);
        var pixel = imageData.data;
 
        var pixelColor = 'rgba('+pixel[0]+', '+pixel[1]+', '+pixel[2]+', '+pixel[3]+')';
        $('#preview').css('backgroundColor', pixelColor);
    });
 
    $('#color').click(function(e) { // mouse click handler
        var canvasOffset = $(canvasColor).offset();
        var canvasX = Math.floor(e.pageX - canvasOffset.left);
        var canvasY = Math.floor(e.pageY - canvasOffset.top);
 
        var imageData = ctxColor.getImageData(canvasX, canvasY, 1, 1);
        var pixel = imageData.data;
 
        var pixelColor = 'rgba('+pixel[0]+', '+pixel[1]+', '+pixel[2]+', '+pixel[3]+')';
        $('#pick').css('backgroundColor', pixelColor);
 
        selColorR = pixel[0];
        selColorG = pixel[1];
        selColorB = pixel[2];
    });
 
    $('#panel').mousedown(function(e) { // mouse down handler
        bMouseDown = true;
        var canvasOffset = $(canvas).offset();
        var canvasX = Math.floor(e.pageX - canvasOffset.left);
        var canvasY = Math.floor(e.pageY - canvasOffset.top);
 
        BubbleBrush.startCurve(canvasX, canvasY, false, false, false, false, false, false, canvasX, canvasY, 0, 0);
    });
    $('#panel').mouseup(function(e) { // mouse up handler
        bMouseDown = false;
    });
    $('#panel').mousemove(function(e) { // mouse move handler
        if (bMouseDown) {
            var canvasOffset = $(canvas).offset();
            var canvasX = Math.floor(e.pageX - canvasOffset.left);
            var canvasY = Math.floor(e.pageY - canvasOffset.top);
 
            BubbleBrush.draw(canvasX, canvasY, false, false, false, false, false, false, canvasX, canvasY, 0, 0);
        }
    });
});
 
function drawGradients() {
    var grad = ctxColor.createLinearGradient(20, 0, canvasColor.width - 20, 0);
    grad.addColorStop(0, 'red');
    grad.addColorStop(1 / 6, 'orange');
    grad.addColorStop(2 / 6, 'yellow');
    grad.addColorStop(3 / 6, 'green')
    grad.addColorStop(4 / 6, 'aqua');
    grad.addColorStop(5 / 6, 'blue');
    grad.addColorStop(1, 'purple');
    ctxColor.fillStyle=grad;
    ctxColor.fillRect(0, 0, canvasColor.width, canvasColor.height);
}