[Gambas-user] Sample code to convert image to b/w image

Safiur Rahman isafiur at gmail.com
Sun Sep 17 04:02:11 CEST 2023

Application using gb.image, gb.image.effect and gb.media in addition to

There are two controls for image:
Drawing Area (dwgVideo) and ImageView (ImageView1)

Private myPlayer As New MediaPlayer As "Player"

Public Sub Button1_Click()

  With myPlayer
    If .State = Media.Playing Then
    .URL = "v4l2://" & ComboBox1.Text
  End With


'While adding values of Opacity or threshold there is error
Public Sub BtnTakeShot_Click()

  Dim ximage As Image

  If myPlayer.State <> Media.Playing Then Return
  ximage = myPlayer.Video.Image

  If chkopacity.Value Then
    ximage = ximage.Opacity(spnopacity.Value)

  If chkthres.Value Then

  ImageView1.Image = ximage


Attached a sample project

On Sun, Sep 17, 2023 at 1:19 AM Safiur Rahman <isafiur at gmail.com> wrote:

> Hi
> I want to achieve the following black-in-white image output with
> Imagemagick with gambas
> $ convert old.png -alpha off -threshold 50% new.png
> Any sample code to achieve it?
> Also using Image.Opacity and Image.Threshold, I get following errors
> With Image.Opacity(50) I am getting error "The image must have an alpha
> channel"
> With Image.Threshold(0.5) the gambas crashed.
> --
> Regards
> Safiur Rahman

Safiur Rahman
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