By: Paul S Cilwa	Posted: 4/10/2026	Page Views: 22
Hashtags: #Namtira #VisualBasic #VBNET #ClassLibrary #NamtiraLib #SuperColors #Color #HSL #HSV #HCL #Contrast
Extension methods and structures for color conversion, manipulation, blending, and accessibility-focused contrast helpers.
Estimated reading time: 11 minute(s) (2527 words)

This module was originally named SuperColors.

.NET's System.Drawing.Color stores RGB values cleanly and integrates well with WinForms and GDI+, but it stops short of offering tools for manipulating color in perceptual or design-oriented ways. There is no built-in support for HSL, HSV, or HCL—color spaces that make tasks like lightening a shade, generating harmonious palettes, or checking contrast far more intuitive. SuperColors fills that gap with three lightweight structures, a set of extension methods on Color, and accessibility helpers that make color manipulation both expressive and mathematically reliable.

Structure HslColor
Member	Parameters	Example
New	`hue, sat, light As Double`	`New HslColor(210, 0.65, 0.45)`
H, S, L	—	`hsl.H` → hue in degrees
ToString	—	`hsl.ToString` → `"HSL(H=210°, ...)"`
Structure HsvColor
New	`hue, sat, value As Double`	`New HsvColor(120, 0.7, 0.9)`
H, S, V	—	`hsv.V` → brightness
ToString	—	`hsv.ToString`
Structure HclColor
New	`hue, chroma, lightness As Double`	`New HclColor(30, 45, 60)`
H, C, L	—	`hcl.L` → CIELAB L* [0..100]
ToString	—	`hcl.ToString`
Module SuperColors—Conversions
ToHSL	(extends `Color`)	`myColor.ToHSL`
ToHSV	(extends `Color`)	`myColor.ToHSV`
ToHCL	(extends `Color`)	`myColor.ToHCL`
FromHSL	`hsl As HslColor`, `alpha As Integer?` (opt)	`FromHSL(hsl, 128)`
FromHSV	`hsv As HsvColor`, `alpha As Integer?` (opt)	`FromHSV(hsv)`
FromHCL	`hcl As HclColor`, `alpha As Integer?` (opt)	`FromHCL(hcl)`
Module SuperColors—Adjustments
Adjust	`percent As Double` (extends `Color`)	`c.Adjust(25)` → lighter
Lighten	`amount As Double` (extends `Color`)	`c.Lighten(0.25)`
Darken	`amount As Double` (extends `Color`)	`c.Darken(0.2)`
RotateHue	`degrees As Double` (extends `Color`)	`c.RotateHue(180)`
Saturate	`amount As Double` (extends `Color`)	`c.Saturate(0.15)`
Desaturate	`amount As Double` (extends `Color`)	`c.Desaturate(0.35)`
WithAlpha	`alpha As Integer` (extends `Color`)	`c.WithAlpha(128)`
Module SuperColors—Blending & Transforms
Blend	`other As Color, t As Double` (extends `Color`)	`red.Blend(blue, 0.5)`
Invert	(extends `Color`)	`c.Invert`
ToGrayscale	(extends `Color`)	`c.ToGrayscale`
Module SuperColors—Accessibility
RelativeLuminance	(extends `Color`)	`bg.RelativeLuminance`
ContrastRatio	`other As Color` (extends `Color`)	`text.ContrastRatio(bg)`
BestForeground	`dark, light As Color?` (opt, extends `Color`)	`bg.BestForeground`
MakeReadable	`background As Color`, `minContrast` (opt), `maxIterations` (opt) (extends `Color`)	`text.MakeReadable(bg)`
Module SuperColors—Hex
ToHex	`includeAlpha As Boolean` (opt, extends `Color`)	`c.ToHex` → `"#3498DB"`
FromHex	`hex As String`	`FromHex("#09F")`

Option Strict On
Option Explicit On

Imports System
Imports System.Drawing
Imports System.Globalization
Imports System.Runtime.CompilerServices

Color-Space Structures

Three value types represent colors in alternative spaces. Each normalizes its inputs on construction so downstream code can assume valid ranges.

HslColor

Stores Hue (degrees), Saturation, and Lightness. HSL is well suited to UI theming because you can reason about lightness directly instead of manually juggling RGB channels.

Public Structure HslColor
    Public ReadOnly H As Double   ' degrees [0, 360)
    Public ReadOnly S As Double   ' [0, 1]
    Public ReadOnly L As Double   ' [0, 1]

    Public Sub New(hue As Double, sat As Double, light As Double)
        H = ColorMath.NormalizeHue(hue)
        S = ColorMath.Clamp01(sat)
        L = ColorMath.Clamp01(light)
    End Sub

    Public Overrides Function ToString() As String
        Return $"HSL(H={H:0.##}°, S={S:0.###}, L={L:0.###})"
    End Function
End Structure

HsvColor

Stores Hue, Saturation, and Value. HSV is often a better mental model for tasks where you want to keep brightness constant while varying saturation.

Public Structure HsvColor
    Public ReadOnly H As Double   ' degrees [0, 360)
    Public ReadOnly S As Double   ' [0, 1]
    Public ReadOnly V As Double   ' [0, 1]

    Public Sub New(hue As Double, sat As Double, value As Double)
        H = ColorMath.NormalizeHue(hue)
        S = ColorMath.Clamp01(sat)
        V = ColorMath.Clamp01(value)
    End Sub

    Public Overrides Function ToString() As String
        Return $"HSV(H={H:0.##}°, S={S:0.###}, V={V:0.###})"
    End Function
End Structure

HclColor

Stores Hue, Chroma, and Lightness based on CIELAB L*. Because its lightness component is perceptual, equal steps in L* feel visually consistent—making HCL ideal for generating balanced palettes.

Public Structure HclColor
    Public ReadOnly H As Double   ' degrees [0, 360)
    Public ReadOnly C As Double   ' Chroma (roughly 0..~150 for sRGB)
    Public ReadOnly L As Double   ' Lightness (CIELAB L*) [0..100]

    Public Sub New(hue As Double, chroma As Double, lightness As Double)
        H = ColorMath.NormalizeHue(hue)
        C = Math.Max(0.0, chroma)
        L = Math.Max(0.0, Math.Min(100.0, lightness))
    End Sub

    Public Overrides Function ToString() As String
        Return $"HCL(H={H:0.##}°, C={C:0.###}, L={L:0.###})"
    End Function
End Structure

Conversions

Extension methods on Color convert to each of the three spaces, and companion module functions convert back. Each From… function accepts an optional alpha value (defaulting to fully opaque).

Public Module SuperColors

    <Extension>
    Public Function ToHSL(c As Color) As HslColor
        Dim h As Double, s As Double, l As Double
        ColorMath.RgbToHsl(c, h, s, l)
        Return New HslColor(h, s, l)
    End Function

    <Extension>
    Public Function ToHSV(c As Color) As HsvColor
        Dim h As Double, s As Double, v As Double
        ColorMath.RgbToHsv(c, h, s, v)
        Return New HsvColor(h, s, v)
    End Function

    <Extension>
    Public Function ToHCL(c As Color) As HclColor
        Dim lch = ColorMath.RgbToLch(c)
        Return New HclColor(lch.h, lch.c, lch.l)
    End Function

    Public Function FromHSL(hsl As HslColor,
                            Optional alpha As Integer? = Nothing) As Color
        Dim a As Integer = If(alpha.HasValue, ColorMath.ClampByte(alpha.Value), 255)
        Dim rgb = ColorMath.HslToRgb(hsl.H, hsl.S, hsl.L)
        Return Color.FromArgb(a, rgb.R, rgb.G, rgb.B)
    End Function

    Public Function FromHSV(hsv As HsvColor,
                            Optional alpha As Integer? = Nothing) As Color
        Dim a As Integer = If(alpha.HasValue, ColorMath.ClampByte(alpha.Value), 255)
        Dim rgb = ColorMath.HsvToRgb(hsv.H, hsv.S, hsv.V)
        Return Color.FromArgb(a, rgb.R, rgb.G, rgb.B)
    End Function

    Public Function FromHCL(hcl As HclColor,
                            Optional alpha As Integer? = Nothing) As Color
        Dim a As Integer = If(alpha.HasValue, ColorMath.ClampByte(alpha.Value), 255)
        Dim rgb = ColorMath.LchToRgb(hcl.L, hcl.C, hcl.H)
        Return Color.FromArgb(a, rgb.R, rgb.G, rgb.B)
    End Function

A typical round-trip looks like this: convert to HSL, tweak lightness, then convert back.

Dim c As Color = Color.CornflowerBlue
Dim hsl As HslColor = c.ToHSL()
Dim lighter As Color = SuperColors.FromHSL(New HslColor(hsl.H, hsl.S, 0.8), c.A)

Adjustments

These extensions modify a single dimension of a color—lightness, hue, or saturation—while leaving the others unchanged. All of them work in HSL space internally.

Adjust

Shifts lightness based on a percentage. Values below 50 lighten; values above 50 darken; 50 leaves the color unchanged.

    <Extension>
    Public Function Adjust(c As Color, percent As Double) As Color
        Dim h As Double, s As Double, l As Double
        ColorMath.RgbToHsl(c, h, s, l)

        Dim p As Double = percent / 100.0
        Dim newL As Double

        If p < 0.5 Then
            Dim t As Double = p / 0.5
            newL = l + (1 - l) * (1 - t)
        ElseIf p > 0.5 Then
            Dim t As Double = (p - 0.5) / 0.5
            newL = l * (1 - t)
        Else
            newL = l
        End If

        Dim rgb = ColorMath.HslToRgb(h, s, ColorMath.Clamp01(newL))
        Return Color.FromArgb(c.A, rgb.R, rgb.G, rgb.B)
    End Function

Lighten / Darken

Lighten moves lightness toward white; Darken moves it toward black. The amount parameter is clamped to [0, 1].

    <Extension>
    Public Function Lighten(c As Color, amount As Double) As Color
        Dim hsl = c.ToHSL()
        Dim newL = hsl.L + (1 - hsl.L) * ColorMath.Clamp01(amount)
        Return FromHSL(New HslColor(hsl.H, hsl.S, newL), c.A)
    End Function

    <Extension>
    Public Function Darken(c As Color, amount As Double) As Color
        Dim hsl = c.ToHSL()
        Dim newL = hsl.L * (1 - ColorMath.Clamp01(amount))
        Return FromHSL(New HslColor(hsl.H, hsl.S, newL), c.A)
    End Function

RotateHue

Rotates hue while keeping saturation and lightness stable—handy for deriving complementary or triadic accents from a single brand color.

    <Extension>
    Public Function RotateHue(c As Color, degrees As Double) As Color
        Dim hsl = c.ToHSL()
        Return FromHSL(New HslColor(hsl.H + degrees, hsl.S, hsl.L), c.A)
    End Function

Saturate / Desaturate

Saturate increases HSL saturation by the given amount; Desaturate delegates to Saturate with a negated value, keeping the clamping behavior consistent.

    <Extension>
    Public Function Saturate(c As Color, amount As Double) As Color
        Dim hsl = c.ToHSL()
        Dim newS = ColorMath.Clamp01(hsl.S + amount)
        Return FromHSL(New HslColor(hsl.H, newS, hsl.L), c.A)
    End Function

    <Extension>
    Public Function Desaturate(c As Color, amount As Double) As Color
        Return c.Saturate(-Math.Abs(amount))
    End Function

WithAlpha

Returns a new Color with the same RGB channels but a different alpha. Useful for translucent overlays, selection rings, and focus indicators.

    <Extension>
    Public Function WithAlpha(c As Color, alpha As Integer) As Color
        Return Color.FromArgb(ColorMath.ClampByte(alpha), c.R, c.G, c.B)
    End Function

Blending and Transforms

Blend

Linearly interpolates all four channels (including alpha) between two colors. The parameter t is clamped to [0, 1], so out-of-range values won't break the output.

    <Extension>
    Public Function Blend(c As Color, other As Color, t As Double) As Color
        Dim x = ColorMath.Clamp01(t)
        Dim a = CInt(Math.Round(c.A + (other.A - c.A) * x))
        Dim r = CInt(Math.Round(c.R + (other.R - c.R) * x))
        Dim g = CInt(Math.Round(c.G + (other.G - c.G) * x))
        Dim b = CInt(Math.Round(c.B + (other.B - c.B) * x))
        Return Color.FromArgb(ColorMath.ClampByte(a),
                              ColorMath.ClampByte(r),
                              ColorMath.ClampByte(g),
                              ColorMath.ClampByte(b))
    End Function

Invert

Flips each RGB channel (255 − channel) while preserving alpha.

    <Extension>
    Public Function Invert(c As Color) As Color
        Return Color.FromArgb(c.A, 255 - c.R, 255 - c.G, 255 - c.B)
    End Function

ToGrayscale

Converts to grayscale using Rec. 709 luma coefficients, which correlate better with perceived brightness than a naive channel average.

    <Extension>
    Public Function ToGrayscale(c As Color) As Color
        Dim y = CInt(Math.Round(0.2126 * c.R + 0.7152 * c.G + 0.0722 * c.B))
        Dim v = ColorMath.ClampByte(y)
        Return Color.FromArgb(c.A, v, v, v)
    End Function

Accessibility and Contrast

RelativeLuminance

Computes the WCAG relative luminance of a color by linearizing sRGB values first. This is the building block for contrast calculations.

    <Extension>
    Public Function RelativeLuminance(c As Color) As Double
        Return ColorMath.RelativeLuminance(c)
    End Function

ContrastRatio

Returns the WCAG contrast ratio between two colors (always ≥ 1). A ratio of 4.5 or above is the threshold for normal-size text; 3.0 suffices for large text.

    <Extension>
    Public Function ContrastRatio(c As Color, other As Color) As Double
        Dim l1 = c.RelativeLuminance()
        Dim l2 = other.RelativeLuminance()
        Dim hi = Math.Max(l1, l2)
        Dim lo = Math.Min(l1, l2)
        Return (hi + 0.05) / (lo + 0.05)
    End Function

BestForeground

Given a background, chooses whichever of two candidate foreground colors (defaulting to black and white) provides the higher contrast ratio.

    <Extension>
    Public Function BestForeground(background As Color,
                                   Optional dark As Color? = Nothing,
                                   Optional light As Color? = Nothing) As Color
        Dim darkC = If(dark.HasValue, dark.Value, Color.Black)
        Dim lightC = If(light.HasValue, light.Value, Color.White)

        Dim cDark = background.ContrastRatio(darkC)
        Dim cLight = background.ContrastRatio(lightC)
        Return If(cDark >= cLight, darkC, lightC)
    End Function

MakeReadable

The most sophisticated helper in the module. Given a text color and a background, it shifts the text color's HSL lightness until the contrast ratio reaches a minimum threshold (defaulting to the WCAG AA value of 4.5). If the original color already meets the threshold, it is returned unchanged. If shifting lightness in both directions fails, the method falls back to black or white.

Semi-transparent text is composited over the background before each contrast check, so the measurement reflects what will actually be drawn.

    <Extension>
    Public Function MakeReadable(textColor As Color,
                                 background As Color,
                                 Optional minContrast As Double = 4.5,
                                 Optional maxIterations As Integer = 48) As Color

        If minContrast < 1.0 Then minContrast = 1.0
        If maxIterations < 1 Then maxIterations = 1

        Dim a As Integer = textColor.A
        Dim effectiveText As Color =
            If(a = 255, textColor, CompositeOver(background, textColor))
        Dim best As Color = textColor
        Dim bestContrast As Double = effectiveText.ContrastRatio(background)

        If bestContrast >= minContrast Then
            Return textColor
        End If

        Dim hsl = textColor.ToHSL()
        Dim bgLum As Double = background.RelativeLuminance()
        Dim txtLum As Double = effectiveText.RelativeLuminance()
        Dim primaryDir As Integer = If(bgLum > txtLum, -1, 1)
        Dim stepSize As Double = 1.0 / maxIterations

        ImproveByShiftingLightness(hsl, a, background, minContrast,
                                   maxIterations, stepSize, primaryDir,
                                   best, bestContrast)
        If bestContrast < minContrast Then
            ImproveByShiftingLightness(hsl, a, background, minContrast,
                                       maxIterations, stepSize, -primaryDir,
                                       best, bestContrast)
        End If

        If bestContrast < minContrast Then
            Dim blackText As Color = Color.FromArgb(a, Color.Black)
            Dim whiteText As Color = Color.FromArgb(a, Color.White)
            Dim effBlack As Color =
                If(a = 255, blackText, CompositeOver(background, blackText))
            Dim effWhite As Color =
                If(a = 255, whiteText, CompositeOver(background, whiteText))
            Dim cBlack As Double = effBlack.ContrastRatio(background)
            Dim cWhite As Double = effWhite.ContrastRatio(background)

            If cBlack >= cWhite AndAlso cBlack > bestContrast Then
                best = blackText
            ElseIf cWhite > bestContrast Then
                best = whiteText
            End If
        End If

        Return best
    End Function

The private helpers ImproveByShiftingLightness and CompositeOver handle the iteration loop and alpha compositing respectively; they are internal to the module and not called directly.

Hex Serialization

ToHex

Serializes a Color to a CSS-style hex string. Pass includeAlpha:=True when you need the full #AARRGGBB form.

    <Extension>
    Public Function ToHex(c As Color,
                          Optional includeAlpha As Boolean = False) As String
        If includeAlpha Then
            Return $"#{c.A:X2}{c.R:X2}{c.G:X2}{c.B:X2}"
        End If
        Return $"#{c.R:X2}{c.G:X2}{c.B:X2}"
    End Function

FromHex

Parses #RGB, #RRGGBB, or #AARRGGBB (with or without the leading #) into a Color. Throws a FormatException if the input doesn't match any of those patterns.

    Public Function FromHex(hex As String) As Color
        If hex Is Nothing Then Throw New ArgumentNullException(NameOf(hex))

        Dim s = hex.Trim()
        If s.StartsWith("#"c) Then s = s.Substring(1)

        If s.Length = 3 Then
            Dim r = Convert.ToInt32(New String(s(0), 2), 16)
            Dim g = Convert.ToInt32(New String(s(1), 2), 16)
            Dim b = Convert.ToInt32(New String(s(2), 2), 16)
            Return Color.FromArgb(255, r, g, b)
        ElseIf s.Length = 6 Then
            Dim r = Integer.Parse(s.Substring(0, 2), NumberStyles.HexNumber,
                                  CultureInfo.InvariantCulture)
            Dim g = Integer.Parse(s.Substring(2, 2), NumberStyles.HexNumber,
                                  CultureInfo.InvariantCulture)
            Dim b = Integer.Parse(s.Substring(4, 2), NumberStyles.HexNumber,
                                  CultureInfo.InvariantCulture)
            Return Color.FromArgb(255, r, g, b)
        ElseIf s.Length = 8 Then
            Dim a = Integer.Parse(s.Substring(0, 2), NumberStyles.HexNumber,
                                  CultureInfo.InvariantCulture)
            Dim r = Integer.Parse(s.Substring(2, 2), NumberStyles.HexNumber,
                                  CultureInfo.InvariantCulture)
            Dim g = Integer.Parse(s.Substring(4, 2), NumberStyles.HexNumber,
                                  CultureInfo.InvariantCulture)
            Dim b = Integer.Parse(s.Substring(6, 2), NumberStyles.HexNumber,
                                  CultureInfo.InvariantCulture)
            Return Color.FromArgb(a, r, g, b)
        End If

        Throw New FormatException(
            "Invalid hex color. Expected RGB(3), RRGGBB(6), or AARRGGBB(8) hex digits.")
    End Function

End Module

The ColorMath Module

All of the heavy lifting—RGB↔HSL, RGB↔HSV, RGB↔XYZ↔Lab↔LCh conversions, sRGB gamma, and utility clamps—lives in a Friend Module ColorMath. Because it is Friend, it is invisible outside the assembly; the public API surface is entirely the structures and extensions shown above.

Canoodling with Colors

By: Paul S Cilwa	Posted: 4/10/2026	Page Views: 21
Hashtags: #RGB #HSL #HSV #HCL #ColorSpaces #ColorTheory #AccessibilityContrast #DigitalColorRepresentation
A guide to how computers represent, manipulate, and display colors.
Estimated reading time: 4 minute(s) (910 words)

As Walt Disney used to remind us every Sunday, the world is a carousel of color. And, thanks to high quality color monitors, smartphones, and other devices, so is the Internet. If you want to create web sites or even boring apps, you still need to know at least the basics of mathematically-calculated colors: How to create them, compare them; how to lighten, darken or ensure readability of one against another.

A Million Little Pieces Of My Mind

NamtiraLib

SuperColors

My Trips

Buying Me A Gift?

If You Like My Site
You'll Probably Like My Books

Highly Recommended Sites

Color-Space Structures

HslColor

HsvColor

HclColor

Conversions

Adjustments

Adjust

Lighten / Darken

RotateHue

Saturate / Desaturate

WithAlpha

Blending and Transforms

Blend

Invert

ToGrayscale

Accessibility and Contrast

RelativeLuminance

ContrastRatio

BestForeground

MakeReadable

Hex Serialization

ToHex

FromHex

The ColorMath Module

Canoodling with Colors

My Trips

Buying Me A Gift?

If You Like My SiteYou'll Probably Like My Books

Highly Recommended Sites

Color-Space Structures

HslColor

HsvColor

HclColor

Conversions

Adjustments

Adjust

Lighten / Darken

RotateHue

Saturate / Desaturate

WithAlpha

Blending and Transforms

Blend

Invert

ToGrayscale

Accessibility and Contrast

RelativeLuminance

ContrastRatio

BestForeground

MakeReadable

Hex Serialization

ToHex

FromHex

The ColorMath Module

Canoodling with Colors

If You Like My Site
You'll Probably Like My Books