Seems I've answered the question myself. Should anyone need this feature, here is a piece of code using Windows Forms.
1st Create a pictureBox
2nd set the mouse properties Up, Down Move
$set ilusing "System.Drawing".
$set ilusing "System.Drawing.Graphics".
$set ilusing "System.IO.Stream".
working-storage
01 Pen type Pen.
01 bmp type Bitmap.
01 g type Graphics.
01 _Previous type Point.
01 mouseval pic 9.
88 mousedown value 1 false 0.
Methods:
method-id pictureBox1_Paint final private.
procedure division using by value sender as object e as type System.Windows.Forms.PaintEventArgs.
set Pen to new Pen(type Color::Black, 3)
end method.
method-id pictureBox1_MouseMove final private.
procedure division using by value sender as object e as type System.Windows.Forms.MouseEventArgs.
if mousedown
if pictureBox1::Image = Null
set bmp to new Bitmap(PictureBox1::Width, PictureBox1::Height)
set g to type Graphics::FromImage(bmp)
invoke g::Clear(type Color::White)
set pictureBox1::Image to bmp
else
invoke g::DrawLine(Pen, _Previous::X, _Previous::Y, e::X, e::Y)
end-if
invoke pictureBox1::Invalidate()
set _Previous::X to e::X
set _Previous::Y to e::Y
end-if
end method.
method-id pictureBox1_MouseDown final private.
procedure division using by value sender as object e as type System.Windows.Forms.MouseEventArgs.
set _Previous to new Point(e::X, e::Y)
set mousedown to true
end method.
method-id pictureBox1_MouseUp final private.
procedure division using by value sender as object e as type System.Windows.Forms.MouseEventArgs.
set mousedown to false
set _Previous to Null
end method.
method-id button2_Click final private.
procedure division using by value sender as object e as type System.EventArgs.
invoke bmp::Save("Signature.bmp", type System.Drawing.Imaging.ImageFormat::Bmp)
set pictureBox1::Image to Null
end method.