Drawing png from database to canvas loses transparency

General
1

I have a png file with transparent background stored in Sqlite database as type picture.
I retrieve the picture to a graphics object and it is still transparent if I look at the graphics object contents in the debug window so I don’t think it has anything to do with the database steps.
When I resize it and draw it to a canvas it has a white background.
Can anyone assist me with this please?

2

If you can create a simple project with a sample sqlite and share by uploading the zip to the forum, someone will take a look.

What version of Xojo? What OS?

3

Mac Ventura latest Xojo

The problem occurs when I put the picture into a graphics object first. I only do this because I want the user to be able to adjust transparency with a slider control.
If I draw the picture straight onto the canvas or make it the backdrop it works fine.

'Print Logo from picture object
if picLogo <> nil then 
  'Get ratio
  ratio = picLogo.Width/picLogo.Height
  dim lHeight as double
  dim lWidth as double
  Static logoViewSize as double = 130
  
  If ratio < 1 Then
    lHeight  =logoViewSize
    lWidth = logoViewSize * ratio
  Else
    lWidth =logoViewSize
    lHeight = logoViewSize / ratio
  End If
  
  'Create graphics object for logo
  Dim reposLogo As New picture(picLogo.width,picLogo.height, 32)
  reposLogo.Graphics.Transparency = sldTransparencyLogo.Value
  reposLogo.graphics.DrawPicture(picLogo,0,0)
  
  'Draw logo
  
  '1. No good - graphics object displays white background
  g.DrawPicture(reposLogo,0,0,lWidth,lHeight)
  
  '2. Good - drawing directly displays transparent background (but user cannot adjust whole image transparency)
  g.DrawPicture(picLogo,0,0,lWidth,lHeight)
4

Simply remove the depth parameter from

Dim reposLogo As New picture(picLogo.width,picLogo.height)
5 Likes
5

Thank you so much Martin. So simple but I never thought of that.
I’m very pleased.

1 Like
6

Why do you need the second picture. Can’t you just do this?

7

Because there are many items drawn to the canvas.
I don’t want everything on the canvas to be transparent when the user adjusts the transparency of individual items such as the background or logo.

8

You could just store the transparency level beforehand in a local variable and then restore it afterwards. If you are doing this all in the Paint event it would be more efficient than using a separate picture.