GAMBAS BOOK 3.19.1

This static class Color (gb.qt4) has properties that return the system colours. Please note that in Gambas there is also a class Color (gb.image) in addition to the class Color (gb.qt4). This static class Color (gb.image) defines constants of predefined colours and contains some useful methods to deal with colours. The fact is that the colour constants and the useful methods are in Color (gb.image) and the system colours are in Color (gb.qt4). The Colour (gb.image) class contains constants and methods that do not depend on specific libraries. The constants are in RGB format. The methods use algorithms written or adapted by Minisini. The system colours, on the other hand, are linked to the current system and are provided by the current toolkit.

The (static) properties are described in the following table:

Table 23.4.2.1.1: Colour constants class Color (gb.qt4)

This class Color (gb.image) is static and defines these colour constants:

Table 23.4.2.1 : Colour constants of the static class Color (gb.image)

The numerous methods of the class Color (gb.image) enable the user to work with colours in Gambas in a qualified manner.

Table 23.4.2.1.2: Methods of the Colour (gb.image) class

In the selected examples, the original colours and the changed colours are displayed in two ColorButtons or three ColorChoosers and the source code used is specified.

Example 1 - Colour.Darker(..)

Public Sub btnDarker_Click()
 
    Dim iSourceColor, iResultColor As Integer
 
    iSourceColor = ColorButton1.Color
    iResultColor = Color.Darker(iSourceColor)
    ColorButton2.Color = iResultColor
'-- ColorButton2.Color = Color.Darker(ColorButton1.Color) '-- Short version
 
End

Example 2 - Colour.Lighter(..)

Public Sub btnLighter_Click()
  ColorButton2.Color =  Color.Lighter(ColorButton1.Color)
End

Example 3 - Colour.Desaturate(..)

Public Sub btnDesaturate_Click()
  ColorButton2.Color =  Color.Desaturate(ColorButton1.Color)
End

Example 4 - Colour.Distance(..)

Public Sub btnDistance_Click()
 
  Dim iColor1, iColor2 As Integer
  Dim fDistance As Float
 
  iColor1 = ColorButton1.Color
  iColor2 = ColorButton2.Color
 
  fDistance = Color.Distance(iColor1, iColor2)
  Print fDistance
 
End

With the two colours red (Color.RGB(255,0,0)) and green (Color.HSV(120,255,255)), this results in a distance value of 0.70710678118655. Isn't that nice! In any case, the author is thrilled - but can't do anything with this value.

Example 5 - Colour.Merge(..)

Public Sub btnMerge_Click()
 
    Dim iColor1, iColor2, iResultColor As Integer
    Dim fWeight As Float
 
'-- Weight is the relative weight of the first color, between 0 and 1.
    iColor1 = ColorButton1.Color
    fWeight = 0.3
    iColor2 = ColorButton2.Color
 
    iResultColor = Color.Merge(iColor1, iColor2, fWeight)
'-- iResultColor = Color.Merge(iColor1, iColor2) ' ---> fWeight = 0.5 (Default)
    ColorButton3.Color = iResultColor
 
End

Example 6 - Colour.Gradient(..)

Public Sub btnGradient_Click()
 
    Dim iColor1, iColor2, iResultColor As Integer
    Dim fWeight As Float
 
    iColor1 = ColorButton1.Color
    iColor2 = ColorButton2.Color
'-- fWeight = 0.0 ' Sonderfall 1
'-- fWeight = 1.0 ' Sonderfall 2
    fWeight = 0.4
 
    iResultColor = Color.Gradient(iColor1, iColor2, fWeight)
'-- iResultColor = Color.Gradient(iColor1, iColor2) ' ---> fWeight = 0.5 (Default)
    ColorButton3.Color = iResultColor
 
End

Example 7 - Colour.Blend(..)

Public Sub btnBlend_Click()
 
    Dim iSourceColor, iDestinationColor, iResultColor As Integer
 
    iSourceColor = ColorButton1.Color
    iSourceColor = Color.SetAlpha(iSourceColor, 190)
    ColorChooser1.SelectedColor = iSourceColor
 
    iDestinationColor = ColorButton2.Color
    iDestinationColor = Color.SetAlpha(iDestinationColor, 90)
    ColorChooser2.SelectedColor = iDestinationColor
 
    iResultColor = Color.Blend(iSourceColor, iDestinationColor)
    Print Color.GetAlpha(iResultColor)
'-- Alternative: Print Color[iResultColor].Alpha
    ColorChooser3.SelectedColor = iResultColor
 
End