Qu'est-ce que les mathématiques derrière la Roue de Couleur

Ont un coup d'oeil à http://www.easyrgb.com il a les algorithmes de nombreuses conversions de couleurs. Voici le RGB -> HSV.

var_R = ( R /255 )                     //RGB from 0 to 255
var_G = ( G /255 )
var_B = ( B /255 )

var_Min = min( var_R, var_G, var_B )    //Min. value of RGB
var_Max = max( var_R, var_G, var_B )    //Max. value of RGB
del_Max = var_Max - var_Min             //Delta RGB value 

V = var_Max

if ( del_Max == 0 )                     //This is a gray, no chroma...
{
   H = 0                                //HSV results from 0 to 1
   S = 0
}
else                                    //Chromatic data...
{
   S = del_Max /var_Max

   del_R = ( ( ( var_Max - var_R ) /6 ) + ( del_Max /2 ) ) /del_Max
   del_G = ( ( ( var_Max - var_G ) /6 ) + ( del_Max /2 ) ) /del_Max
   del_B = ( ( ( var_Max - var_B ) /6 ) + ( del_Max /2 ) ) /del_Max

   if      ( var_R == var_Max ) H = del_B - del_G
   else if ( var_G == var_Max ) H = ( 1 /3 ) + del_R - del_B
   else if ( var_B == var_Max ) H = ( 2 /3 ) + del_G - del_R

   if ( H < 0 ) H += 1
   if ( H > 1 ) H -= 1
}

OriginalL'auteur

J'ai été jouer avec la prise d'une LGV à base de roue de couleur en VBA Excel, à l'aide de minuscules cellules comme des "pixels", et il s'est avéré assez bien, donc je pensais que je voudrais partager.

Cela démontre la conversion entre les HSL et RGB ainsi que la procédure de programmation pour tracer des lignes/des cercles sur toute la grille — même les cellules de feuille de calcul.

Le code est prêt à exécuter en tant que-est:

Option Explicit
Const colorSheetName = "COLORS"
Const pi = 3.14159265358979
Const squareSize = 3.75             'cell square size (pts)
Const cDiameter = 80#               'circle diameter (cells)
Const numAngles = 360#              'number of angles (lines to draw)
Sub CalculateColorWheel()
Dim ws As Worksheet, radsPerAngle As Double, radius As Long, xStop As Double, _
yStop As Double, z As Integer, xyLength As Double, lineDot As Long, _ 
lineLength As Long, h As Byte, s As Byte, v As Byte, r As Byte, g As Byte, b As Byte
Set ws = ThisWorkbook.Sheets.Add                        'create new worksheet
On Error Resume Next                                    'ignore error 
Application.DisplayAlerts = False                       'ignore warning
ThisWorkbook.Sheets(colorSheetName).Delete              'delete worksheet (if exists)
Application.DisplayAlerts = True                        'stop ignoring warnings
On Error GoTo 0                                         'stop ignoring errors
With ws
.Name = colorSheetName                              'name the new sheet
.Rows.RowHeight = squareSize                        'set rowheight 
.Columns.ColumnWidth=widthToColumnWidth(squareSize) 'match columnwidth to row
ActiveWindow.DisplayGridlines = False               'hide gridlines
ActiveWindow.DisplayHeadings = False                'hide row/col headings
radius = cDiameter / 2                              'centre point
lineLength = radius * 1.5                           'dots per angle (line)
radsPerAngle = (360 / numAngles) * pi / 180         'radians=a(degrees)×pi÷180°
Debug.Print "Grid size=" & .[a1].Height & "×" & .[a1].Width _
& ", Diameter:" & cDiameter _
& ", Area=" & Round(pi * radius ^ 2, 0) _
& ", Circumference=" & Round(2 * pi * radius, 0) _
& ", Radians per Angle=" & Round(radsPerAngle, 3) _
& " × " & numAngles & " angles"                 'stats
For z = 0 To numAngles - 1  'loop through each angle
For lineDot = 1 To lineLength   'loop thru length of line
xyLength = radius * (lineDot / lineLength)  'calc dot xy& offset top-left
xStop = Int(Cos(radsPerAngle * z) * xyLength) + radius + 2 'x (column)
yStop = Int(Sin(radsPerAngle * z) * xyLength) + radius + 2 'y (row)
If .Cells(yStop, xStop).Interior.Pattern=xlNone Then 'skip colored cells
h = ((z + 1) / numAngles) * 255                'hue=angle
s = (lineDot / lineLength) * 255                    'saturation=radius
v = 255                    'maximum brightness. (Adjustable)
HSVtoRGB h, s, v, r, g, b                      'convert HSV to RGB
.Cells(yStop, xStop).Interior.Color=rgb(r,g,b) 'color the cell
dots = dots + 1
End If
Next lineDot
Application.StatusBar = Format(z / (numAngles - 1), "0%") 
DoEvents    'don't lag
Next z
End With
Beep
Application.StatusBar = "Finished drawing color circle (" & dots & " colors)"
End Sub
Public Function widthToColumnWidth(pts As Double) As Double
'convert desired column width (points) to Excel "ColWidthUnits"
'12pts and under is a 1:12 ratio of (colWidthUnits:Pts).
' Over 12pts: 1:12 for 1st unit, then 1:(75/11) for remainder
Select Case pts
Case Is <= 0:  widthToColumnWidth = 0
Case Is <= 12: widthToColumnWidth = pts / 12
Case Else:     widthToColumnWidth = 1 + (pts - 12) / (75 / 11) '
End Select
End Function
Public Sub HSVtoRGB(h As Byte, s As Byte, v As Byte, r As Byte, g As Byte, b As Byte)
Dim minV As Byte, maxV As Byte, Chroma As Byte, tempH As Double
If v = 0 Then
r = 0: g = 0: b = 0
Else
If s = 0 Then
r = v: g = v: b = v:
Else
maxV = v: Chroma = s / 255 * maxV: minV = maxV - Chroma
Select Case h
Case Is >= 170: tempH = (h - 170) / 43: g = 0
If tempH < 1 Then
b = maxV: r = maxV * tempH
Else: r = maxV: b = maxV * (2 - tempH): End If
Case Is >= 85:  tempH = (h - 85) / 43: r = 0
If tempH < 1 Then
g = maxV: b = maxV * tempH
Else: b = maxV: g = maxV * (2 - tempH): End If
Case Else:      tempH = h / 43: b = 0
If tempH < 1 Then
r = maxV: g = maxV * tempH
Else: g = maxV: r = maxV * (2 - tempH): End If
End Select
r = r / maxV * (maxV - minV) + minV
g = g / maxV * (maxV - minV) + minV
b = b / maxV * (maxV - minV) + minV
End If
End If
End Sub

La façon d'exécuter cette dans Excel: Coller le code ci-dessus et collez-le dans un module normal. (Sélectionnez le code, Ctrl+C copier, puis, dans Excel, maintenez la touche Alt et appuyez sur F11+I+M, puis Ctrl+V pour coller, et F5 pour fonctionner.)

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Plus D'Informations:

• Wikipédia: HSL et HSV
• Wikipédia: Roue de Couleur - HSL
• colormatters.com : la Base de la Théorie de la Couleur
• Wikipédia : Milieu du cercle de l'algorithme

OriginalL'auteur