GAMBAS BOOK 3.19.1

The gb.image.effect component has two classes:

1. class Image: It extends the original Image class with effect methods.
2. class ImageHistogram: It presents the image histogram of a selected image.

The description of the ImageHistogram class can be found in the following chapter 24.4.2.7.

The Image class (gb.image.effect)

• reimplements the Image class from gb.image,
• adds many constants and effect methods to the original Image class and
• can be created.

How to create a new image object:

  Dim hImage As Image
  hImage = New Image ( [ Width As Integer, Height As Integer, Color As Integer, Format As Integer ] )

All parameters are optional. If colour is specified, the image is initially filled with this colour. Otherwise, the image content is undefined. Format can be one of the following values: Standard (0) or Premultiplied (1).

You can find out about the current 21 constants of the class at https://gambaswiki.org/wiki/comp/gb.image.effect/image Status: November 2023.

The class has the following static method Gradient(…):

Static Function Gradient (Width As Integer,Height As Integer,SrcColor As Integer,DstColor As Integer,Orientation As Integer [,XDecay As Float,YDecay As Float]) As Image

The function creates a colour gradient image:

• Width is the width and Height is the height of the resulting image.
• SrcColor is the start colour and DstColor is the end colour.
• Orientation is the orientation of the colour gradient, the values of which are specified in the list below.
• XDecay is the x-decay length with a value between -1 and 1 (optional).
• YDecay is the length of the y-decay with a value between -1 and 1 (optional).

The Orientation parameter can take one of the following values:

• Image.Vertical for a vertical colour gradient.
• Image.Horizontal for a horizontal colour gradient.
• Image.Diagonal for a diagonal colour gradient.
• Image.Cross for a diagonal colour gradient.
• Image.Pyramid for a pyramid-shaped colour gradient.
• Image.Rectangle for a rectangular colour gradient.
• Image.PipeCross for a pipe cross gradient.
• Image.Elliptic for an elliptical gradient.

The gradient generated is linear by default - exponential with XDecay and/or YDecay.

Example of a diagonal gradient (red → yellow) with additionally inserted image:

Figure 23.4.2.6.1: Gradient(…) method

Source code snippet

    Public imgCurrent As Image
    Public imgExtern As Image
 
    lblChanged.Text = "G R A D I E N T >> L I N E A R"
    imgCurrent = Image.Gradient(355, 242, Color.Red, Color.Yellow, Image.Diagonal)
    imgExtern = Image.Load("images/hl.png")
    imgCurrent.PaintImage(imgExtern, 60, 50, imgExtern.W * 2, imgExtern.H * 2)
    pboxChanged.Picture = imgCurrent.Picture

The new implementation of Image in gb.image.effect has been supplemented with these filter and effect methods compared to Image (gb.image):

Table 23.4.2.6.1 : Methods of the Image class (gb.image.effect)

An example is presented for each of the methods of the Image (gb.image.effect) class. If the methods use parameters, then these and the images - the original and the modified one - are displayed. The source code used in each case is also shown in extracts.

Example 1 - Image.Swirl(φ) method

The method swirls an image in the centre by a certain angle φ. For negative values, the image is rotated clockwise - otherwise anti-clockwise.

Figure 23.4.2.6.2: Swirl(-163°) method

Source code snippet

    lblChanged.Text = "C H A N G E D  >>  " & "S W I R L (…)"
 
    lblValue.Text = hSliderV.Value & "°"
 
'-- Angle of rotation in radians
    pboxChanged.Picture = imgOriginal.Swirl(Rad(hSliderV.Value), Color.Red).Picture

Example 2 - Image.OilPaint(…) method

The method creates an oil painting effect that only presents the effect well with small parameter values:

Figure 23.4.2.6.3: OilPaint(2) method

Source code snippet

    lblChanged.Text = "C H A N G E D  >>  " & "O I L P A I N T (…)"
 
    lblValue.Text = hSliderV.Value
    pboxChanged.Picture = imgCurrent.OilPaint(hSliderV.Value).Picture

Example 3 - Image.Emboss( ) method

The method creates an embossing effect:

Figure 23.4.2.6.4: Emboss() method

Source code snippet

Public Sub btnDoEmboss_Click()
 
  lblValue.Visible = False
  hSliderV.Visible = False
  lblChanged.Text = "C H A N G E D  >>  " & "E M B O S S ( )"
  imgChanged = imgOriginal.Emboss()
  pboxChanged.Picture = imgChanged.Picture
End

Example 4 - Image.Invert(…) method

The method inverts a complete image or only some of its colour channels. In the example, the inversion takes place in two stages:

Figure 23.4.2.6.5: Invert(…) method

Source code snippet

Public Sub btnDoInvertAll_Click()
 
  lblChanged.Text = "C H A N G E D  —>  " & "I N V E R T  A L L(...)"
  imgCurrent = imgOriginal
  imgCurrent.Invert(Image.Red Or Image.Green)
  imgCurrent.Invert(Image.All)
  pboxChanged.Picture = imgCurrent.Picture
 
End