Heat Map background colour calculations
using System;
using System.Collections.Generic;
using System.Text;
namespace TfsScorecard.Utilities
{
/// <summary>
/// Heat Map background colour calculations
/// Derived from: http://blogs.technet.com/andrew/archive/2007/12/06/heat-maps-in-sql-server-reporting-services-2005.aspx
/// </summary>
public class HeatMap
{
#region Public Method
/// <summary>
///
/// </summary>
/// <param name="redStartVal"></param>
/// <param name="yellowStartVal"></param>
/// <param name="greenStartVal"></param>
/// <param name="val"></param>
/// <returns>The RGB hex color string</returns>
public static string GetColor(decimal redStartVal, decimal yellowStartVal, decimal greenStartVal, decimal val)
{
// color points
int[] Red = new int[] { 255, 255, 255 }; // #FCBF7B
int[] Yellow = new int[] { 254, 255, 132 }; // #FEEB84
int[] Green = new int[] { 99, 190, 123 }; // #63BE7B
int[] White = new int[] { 255, 255, 255 }; // #FFFFFF
// value that corresponds to the color that represents the tier above the value - determined later
Decimal highValue = 0.0M;
// value that corresponds to the color that represents the tier below the value
Decimal lowValue = 0.0M;
// next higher and lower color tiers (set to corresponding member variable values)
int[] highColor = null;
int[] lowColor = null;
// 3-integer array of color values (r,g,b) that will ultimately be converted to hex
int[] rgb = null;
// If value lower than green start value, it must be green.
if (val <= greenStartVal)
{
rgb = Green;
}
// determine if value lower than the baseline of the red tier
else if (val >= redStartVal)
{
rgb = Red;
}
// if not, then determine if value is between the red and yellow tiers
else if (val > yellowStartVal)
{
highValue = redStartVal;
lowValue = yellowStartVal;
highColor = Red;
lowColor = Yellow;
}
// if not, then determine if value is between the yellow and green tiers
else if (val > greenStartVal)
{
highValue = yellowStartVal;
lowValue = greenStartVal;
highColor =Yellow;
lowColor = Green;
}
// must be green
else
{
rgb = Green;
}
// get correct color values for values between dark red and green
if (rgb == null)
{
rgb = GetColorValues(highValue, lowValue, highColor, lowColor, val);
}
// return the hex string
return String.Format("#{0:x}{1:x}{2:x}", rgb[0], rgb[1], rgb[2]);
}
#endregion
/// <summary>
/// Looks at the passed in value and high and low boundary values and determines the
/// relative color values (rgb) in proportion to the relative distance the value is found
/// between the boundaries. The rgb color string is calculated proportionately between the
/// highColor/lowColor commensurate with the proportions the passed-in value exists within
/// the boundary values
/// </summary>
/// <param name="highBound">closest decimal boundary above the value (val)</param>
/// <param name="lowBound">closest decimal boundary above the value (val)</param>
/// <param name="highColor">color (int[] {r,g,b}) that corresponds to the highBound</param>
/// <param name="lowColor">color (int[] {r,g,b}) that corresponds to the lowBound</param>
/// <param name="val">pass rate</param>
/// <returns>a 3-member int[] array (rgb)</returns>
private static int[] GetColorValues(decimal highBound, decimal lowBound, int[] highColor, int[] lowColor, decimal val)
{
// proportion the val is between the high and low bounds
decimal ratio = (val - lowBound) / (highBound - lowBound);
int[] rgb = new int[3];
// step through each color and find the value that represents the approriate proportional value
// between the high and low colors
for (int i = 0; i < 3; i++)
{
int hc = (int)highColor[i];
int lc = (int)lowColor[i];
// high color is lower than low color - reverse the subtracted vals
bool reverse = hc < lc;
// difference between the high and low values
int diff = reverse ? lc - hc : hc - lc;
// lowest value of the two
int baseVal = reverse ? hc : lc;
rgb[i] = (int)Math.Round((decimal)diff * ratio) + baseVal;
}
return rgb;
}
}
}
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