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* ColourGradient.js
*
*
* Copyright (c) 2011 Greg Ross
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of the project's author nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
/**
* Class that is used to define a path through RGB space.
* @author Greg Ross
* @constructor
* @param minValue the value that will return the first colour on the path in RGB space
* @param maxValue the value that will return the last colour on the path in RGB space
* @param rgbColourArray the set of colours that defines the dirctional path through RGB space.
* The length of the array must be greater than two.
*/
ColourGradient = function(minValue, maxValue, rgbColourArray)
{
function RGB2HTML(red, green, blue)
{
var decColor = red + 256 * green + 65536 * blue;
return decColor.toString(16);
}
/**
* Return a colour from a position on the path in RGB space that is proportioal to
* the number specified in relation to the minimum and maximum values from which the
* bounds of the path are derived.
* @member greg.ross.visualisation.ColourGradient
* @param value
*/
this.getColour = function(value)
{
if (value < minValue || value > maxValue || rgbColourArray.length == 1)
{
var colr = {
red: rgbColourArray[0].red,
green:rgbColourArray[0].green,
blue:rgbColourArray[0].blue
};
return colr;
}
var scaledValue = mapValueToZeroOneInterval(value, minValue, maxValue);
return getPointOnColourRamp(scaledValue);
}
function getPointOnColourRamp(value)
{
if (value+""=="NaN") {
value=0;
}
var numberOfColours = rgbColourArray.length;
var scaleWidth = 1 / (numberOfColours - 1);
var index = (value / scaleWidth);
var index = parseInt(index + "");
index = index == (numberOfColours - 1) ? index - 1 : index;
var rgb1 = rgbColourArray[index];
var rgb2 = rgbColourArray[index + 1];
var closestToOrigin, furthestFromOrigin;
if (distanceFromRgbOrigin(rgb1) > distanceFromRgbOrigin(rgb2))
{
closestToOrigin = rgb2;
furthestFromOrigin = rgb1;
}
else
{
closestToOrigin = rgb1;
furthestFromOrigin = rgb2;
}
var t;
if (closestToOrigin == rgb2)
t = 1 - mapValueToZeroOneInterval(value, index * scaleWidth, (index + 1) * scaleWidth);
else
t = mapValueToZeroOneInterval(value, index * scaleWidth, (index + 1) * scaleWidth);
var diff = [
t * (furthestFromOrigin.red - closestToOrigin.red),
t * (furthestFromOrigin.green - closestToOrigin.green),
t * (furthestFromOrigin.blue - closestToOrigin.blue)];
var r = closestToOrigin.red + diff[0];
var g = closestToOrigin.green + diff[1];
var b = closestToOrigin.blue + diff[2];
r = parseInt(r);
g = parseInt(g);
b = parseInt(b);
var colr = {
red:r,
green:g,
blue:b
};
return colr;
}
function distanceFromRgbOrigin(rgb)
{
return (rgb.red * rgb.red) + (rgb.green * rgb.green) + (rgb.blue * rgb.blue);
}
function mapValueToZeroOneInterval(value, minValue, maxValue)
{
if (minValue == maxValue) return 0;
var factor = (value - minValue) / (maxValue - minValue);
return factor;
}
}
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