GAMBAS BOOK 3.19.1

This project centres on the display of an image to which an image shadow is added. The original image should fulfil certain requirements - such as a transparent background - so that the addition of the image shadow provides a good effect.

Figure 23.3.5.5.1: Original image

Figure 23.3.5.5.2: Original image with shadow

The shadow effect can be seen most clearly if you start the project and look at both images one after the other.

The first project uses the (partial) programme 'convert' from the programme collection 'ImageMagick', which must therefore be installed on your system. You can install the programme and its documentation under Ubuntu using this instruction:

sudo apt-get install imagemagick imagemagick-doc 

If you do not want to use the external programme, there is another project in the second section that only uses Gambas methods.

Source code 1:

[1] ' Gambas class file
[2] 
[3] Public Sub Form_Open()
[4]    Me.Center
[5]    Me.Resizable = False
[6]    picBox.Picture = Picture[Application.Path & "/logo.png"]
[7]    If Exist(Application.Path & "/logos.png") Then
[8]       Kill Application.Path & "/logos.png"
[9]    Endif
[10]    btnGenerateShadow.Text = "Schatten ein ..."
[11] End
[12] 
[13] Public Sub btnGenerateShadow_Click()
[14]   Dim sCommand As String
[15] 
[16] ' The 'convert' programme must be installed on the system
[17]   sCommand = "convert -background gray -shadow 80x3 " & Application.path & "/logo.png " 
                & Application.path & "/logos.png"
[18]   Shell sCommand Wait
[19]   MakeShadow()
[20] 
[21] End
[22] 
[23] Public Sub MakeShadow()
[24]   Dim Foreground, Shadow, hImage As Image 
[25] 
[26]   Shadow = Image.Load(Application.path & "/logos.png")
[27]   Foreground = Image.Load(Application.path & "/logo.png")
[28]    
[29]   If btnGenerateShadow.Text = "Schatten ein ..." Then
[30]      hImage = Shadow.Copy()
[31]      hImage.PaintImage(Foreground, 0, 0)
[32]      btnGenerateShadow.Text = "Schatten aus ..."
[33]   Else
[34]      hImage = Foreground.Copy()
[35]      btnGenerateShadow.Text = "Schatten ein ..."
[36]   Endif 
[37]    
[38]   picBox.Picture = hImage.Picture
[39]   
[40] End

Comment:

• At programme start, the original image is displayed in a PictureBox and an existing shadow image is deleted if it exists in the specified path → lines 6 to 9.
• In lines 17 and 18, a shadow image is created from the original image using the 'convert' programme and saved in the path of the original image file in an image file 'logos.png'.
• In the 'MakeShadow' procedure, depending on the text on the btnGenerateShadow button, either the original image is displayed or a third temporary image (hImage of type Image) is generated from the original image and shadow image and then displayed.
• The temporary image is created by drawing (line 31) the original image onto the shadow image, as can be seen in lines 26 to 32.

In the following variant by Tobias Boege and Ingo Beckert, only Gambas methods are used to create the same shadow effect.

Figures 23.3.5.5.3: Original image and image with shadow

Source code 2 for the alternative project is also shown here in full:

[1] ' Gambas class file
[2] 
[3] Public Sub Form_Open()
[4]   Me.Center
[5]   Me.Resizable = False
[6]   picBox.Picture = Picture[Application.Path & "/logo.png"]
[7]   btnGenerateShadow.Text = "Schatten ein ..."
[8] End
[9] 
[10] Public Sub btnGenerateShadow_Click()
[11]   MakeShadow
[12] End
[13] 
[14] Public Sub MakeShadow()
[15]   Dim Foreground, hImage As Image 
[16]    
[17]   Foreground = Image.Load(Application.path & "/logo.png")
[18]    
[19]   If btnGenerateShadow.Text = "Schatten ein ..." Then
[20]      hImage = Foreground.Copy()
[21]      hImage.PaintImage(Foreground, 0, 0)
[22]      picBox.Picture = AddShadow(picBox.Picture.Image).Picture
[23]      btnGenerateShadow.Text = "Schatten aus ..."
[24]   Else
[25]      hImage = Foreground.Copy()
[26]      picBox.Picture = hImage.Picture
[27]      btnGenerateShadow.Text = "Schatten ein ..."
[28]   Endif 
[29]    
[30] End
[31] 
[32] Public Function AddShadow(hImage As Image) As Image
[33]   Dim hNewImage As New Image(hImage.W, hImage.H)
[34] 
[35]   Paint.Begin(hNewImage)
[36]     Paint.DrawImage(Shadow(hImage), 4, 4)
[37]     Paint.DrawImage(hImage, 0, 0)
[38]   Paint.End()   
[39]   Return hNewImage
[40]    
[41] End
[42] 
[43] Public Function Shadow(hImage As Image) As Image
[44]   Dim hShadow As Image = hImage.Copy()
[45] 
[46]   hShadow.Fuzzy(3)
[47]   hShadow.Colorize(Color.Gray)
[48]   hShadow.Opacity(0.5)
[49]   Return hShadow
[50]   
[51] End