GAMBAS-BOOK 3.19.5

The class Cairo of the component Cairo (gb.cairo) is used for drawing on an image (data type Image) or a surface (Surface).

• Before you draw something, you must call the Begin(Device) method. As an argument, specify the surface on which you want to draw (Image, CairoPdfSurface, CairoPsSurface or CairoSvgSurface).
• You can then use methods of the Cairo class to draw text or lines or to fill surfaces with different colours and patterns.
• When the drawing is finished, call the End() method.

Example:

Private Sub GeneratePDF()
  Dim sPfadBildDatei As String
  Dim imgImage As Image  
  Dim PDFSurface As CairoPdfSurface
 
  sPfadBildDatei = Application.Path &/ "fractal.png"
  imgImage = Image.Load(sPfadBildDatei)  
  PDFSurface = New CairoPdfSurface(sPfadPDFDatei, 210, 297) ' -->> DIN A4 surface
 
  Cairo.Begin(PDFSurface)    
    Cairo.Matrix.Translate(MMToPoints(20), MMToPoints(20))
    Cairo.Matrix.Scale(1, 1) '-- Zoom-Factor = 1        
    Cairo.Arc(MMToPoints(80), MMToPoints(75), MMToPoints(70)) '-- Circle
    Cairo.Clip() '-- Clip-Method
    If Exist(sPfadBildDatei) Then
       Cairo.Source = Cairo.ImagePattern(imgImage, 0, 0)
       Cairo.Paint()
    Endif   
  Cairo.End
 
  PDFSurface.Finish()
  Desktop.Open(sPfadPDFDatei)
 
End

Figure 25.1.1.1: Circular clip area with underlaid image