'NOTICE: This code is provided "AS-IS" with no warranties, and confers no rights.

public const ColorScaleRed = "#F8696B"
public const ColorScaleYellow = "#FFEB84"
public const ColorScaleGreen = "#63BE7B"
public const ColorScaleBlue = "#5A8AC6"

public function ColorScaleRYG(value, minValue, maxValue) as string

	ColorScaleRYG = ColorScale3(value, _
		minValue, ColorScaleRed, _
		ColorScaleYellow, _
		maxValue, ColorScaleGreen)

end function

public function ColorScaleGYR(value, minValue, maxValue) as string

	ColorScaleGYR = ColorScale3(value, _
		minValue, ColorScaleGreen, _
		ColorScaleYellow, _
		maxValue, ColorScaleRed)

end function

public function ColorScaleRYB(value, minValue, maxValue) as string

	ColorScaleRYB = ColorScale3(value, _
		minValue, ColorScaleRed, _
		ColorScaleYellow, _
		maxValue, ColorScaleBlue)

end function

public function ColorScaleBYR(value, minValue, maxValue) as string

	ColorScaleBYR = ColorScale3(value, _
		minValue, ColorScaleBlue, _
		ColorScaleYellow, _
		maxValue, ColorScaleRed)

end function

public function ColorScaleRWB(value, minValue, maxValue) as string

	ColorScaleRWB = ColorScale3(value, _
		minValue, ColorScaleRed, _
		"White", _
		maxValue, ColorScaleBlue)

end function

public function ColorScaleBWR(value, minValue, maxValue) as string

	ColorScaleBWR = ColorScale3(value, _
		minValue, ColorScaleBlue, _
		"White", _
		maxValue, ColorScaleRed)

end function

public function ColorScaleRY(value, minValue, maxValue) as string

	ColorScaleRY = ColorScale(value, _
		minValue, ColorScaleRed, _
		maxValue, ColorScaleYellow)

end function

public function ColorScaleYR(value, minValue, maxValue) as string

	ColorScaleYR = ColorScale(value, _
		minValue, ColorScaleYellow, _
		maxValue, ColorScaleRed)

end function

public function ColorScaleGY(value, minValue, maxValue) as string

	ColorScaleGY = ColorScale(value, _
		minValue, ColorScaleGreen, _
		maxValue, ColorScaleYellow)

end function

public function ColorScaleYG(value, minValue, maxValue) as string

	ColorScaleYG = ColorScale(value, _
		minValue, ColorScaleYellow, _
		maxValue, ColorScaleGreen)

end function

public function ColorScale3(value as object, minValue as object, minColor as string, midColor as string, maxValue as object, maxColor as string) as string

	' Use average of minValue and maxValue as midValue
	dim midValue as object
	if IsNumeric(minValue) and IsNumeric(maxValue) then
		midValue = (CDbl(minValue) + CDbl(maxValue)) / 2
	end if

	ColorScale3 = ColorScale3(value, _
		minValue, minColor, _
		midValue, midColor, _
		maxValue, maxColor)

end function

public function ColorScale3(value as object, minValue as object, minColor as string, midValue as object, midColor as string, maxValue as object, maxColor as string) as string

	if IsNumeric(value) and IsNumeric(midValue) and CDbl(value) < CDbl(midValue) then
		ColorScale3 = ColorScale(value, minValue, minColor, midValue, midColor)
	else
		ColorScale3 = ColorScale(value, midValue, midColor, maxValue, maxColor)
	end if

end function

public function ColorScale(value as object, minValue as object, minColor as string, maxValue as object, maxColor as string, optional errorColor as string = "Transparent") as string

	ColorScale = errorColor

	if not IsNumeric(value) or not IsNumeric(minValue) or not IsNumeric(maxValue) then
		exit function
	end if

	' Do all calculations using doubles (can't mix doubles and decimals)
	value = CDbl(value)
	minValue = CDbl(minValue)
	maxValue = CDbl(maxValue)

	if minValue >= maxValue then
		exit function
	end if

	if value <= minValue then
		ColorScale = minColor
		exit function
	end if
	if value >= maxValue then
		ColorScale = maxColor
		exit function
	end if

	dim scaleValue, r, g, b as double
	dim minRGB, minR, minG, minB as integer
	dim maxRGB, maxR, maxG, maxB as integer

	scaleValue = (value - minValue) / (maxValue - minValue)

	minRGB = GetRGB(minColor)
	minR = minRGB / 2^16
	minG = (minRGB mod 2^16) / 2^8
	minB = minRGB mod 2^8

	maxRGB = GetRGB(maxColor)
	maxR = maxRGB / 2^16
	maxG = (maxRGB mod 2^16) / 2^8
	maxB = maxRGB mod 2^8

	r = minR + ((maxR - minR) * scaleValue)
	g = minG + ((maxG - minG) * scaleValue)
	b = minB + ((maxB - minB) * scaleValue)
	
	ColorScale = string.Format("#{0:X2}{1:X2}{2:X2}", _
		CInt(Math.Floor(r)), _
		CInt(Math.Floor(g)), _
		CInt(Math.Floor(b)))

end function

private function GetRGB(colorStr as string) as integer

	GetRGB = 0

	if colorStr.StartsWith("#") then
		GetRGB = Int32.Parse(colorStr.Substring(1), System.Globalization.NumberStyles.AllowHexSpecifier)
		exit function
	end if

	dim c as System.Drawing.Color
	c = System.Drawing.Color.FromName(colorStr)

	GetRGB = (c.R * 2^16) + (c.G * 2^8) + c.B

end function