GAMBAS BOOK 3.19.1

This project shows you how to add text to an image using methods of the Cairo class:

Figure 25.1.11.1: Original

The source code for project 1 is very short:

[1] ' Gambas class file
[2] 
[3] Public hImage As Image
[4] 
[5] Public Sub Form_Open()
[6] ' Create an image
[7]   hImage = Image.Load(Application.Path &/ "images/augentrost.jpg")
[8]   
[9] ' Scale programme window appropriately to the image size
[10]   FMain.W = hImage.W + 2 * Desktop.Scale
[11]   FMain.H = hImage.H + 2 * Desktop.Scale
[12]   FMain.Center()
[13]   FMain.Resizable = False
[14]   
[15]   DrawToImage()
[16] 
[17] End
[18] 
[19] Public Sub DrawToImage()
[20]   Dim sText1, sText2 As String
[21]     
[22]   Cairo.Begin(hImage)
[23]   ' Cairo.Rotate(Pi / 2) '-- Alternative: Rotate text by a specific angle
[24]   ' Draw texts on the image object  
[25]     Cairo.MoveTo(10, 260)
[26]     Cairo.Font.Name = "Sans Serif" '-- Draw texts on the image object
[27]     Cairo.Font.Size = 18.5
[28]     Cairo.Font.Bold = True
[29]     Cairo.Source = Cairo.ColorPattern(Color.Yellow)
[30]     sText1 = "FLORA DER ALPEN"
[31]     Cairo.DrawText(sText1)
[32]   ' -----------------------------------------------------------------  
[33]     sText2 = "Augentrost (Euphrasia minima) - Sonthofen - Juli 2012"
[34]     Cairo.MoveTo(10, 260 + Cairo.TextExtents(sText2).Height + 4)
[35]     Cairo.Font.Size = 13.3
[36]     Cairo.Font.Bold = False
[37]     Cairo.Font.Slant = Cairo.FontSlantNormal
[38]     Cairo.Source = Cairo.ColorPattern(Color.White)
[39]     Cairo.DrawText(sText2)
[40]   Cairo.End()
[41]   
[42] End
[43] 
[44] Public Sub dwgArea_Draw()
[45] ' Display of the image: Insert image into the DrawingArea with a Paint method
[46]   Paint.DrawImage(hImage, 0, 0, hImage.W, hImage.H)
[47] ' Save image
[48]   hImage.Save(Application.Path &/ "images/image.png")
[49] End

Comment:

• An image is created using the instructions in lines 3 and 7.
• The two texts are drawn on this image in different colours and sizes.
• The standard font for Cairo is 'Sans Serif' and should be used especially when the programme is passed on!
• The second text must be placed before the instruction in line 34, as this text is used as an argument in the Cairo.TextExtents(..) method.
• Line 46 contains the instruction to display the Image object - which previously only existed in memory - in a DrawingArea.
• In order to be able to process the labelled image further, it is saved in the project under a fixed image file name in the project folder.

Alternatively, you can also add an open and save dialogue for the image and read in the texts using suitable components.

The result is impressive, as the dominant colours from the image have been used for the font colours:

Figure 25.1.11.2: Image with text