Re: Reloading a Bitmap

Hi James,

On 18/06/15 15:19, James Lynes wrote:
>
> SetBitmap works, as in:
>
> Â Â Â  $frame->{bmp} = Wx::Bitmap->new("dwf.png", wxBITMAP_TYPE_PNG);
> Â Â Â  $frame->{sbm}->SetBitmap($frame->{bmp});
>
> Where $frame->{sbm} is a Static Bitmap.
Ok, mine works too, I don quite know why the demo doesn't.  I write all 
over my bitmap and refresh it all the time.
>
> When I create a new bitmap assigned to $frame->{sbm}, is the system 
> reclaiming the memory used by the old bitmap?
I don't know about this, but it would be a property of the wxWidgets 
c-code, so it would be a question for their mailing list.  To avoid 
issues whenever I scale an image for something, I save a copy of the 
scaled image which I then use as the source next time.  Scaled images 
use up very little disc space compared to videos and so on.
>
> I saw in the wxWidgets docs that there is a Bitmap method 
> newFromPNGData that appears to not be wrapped. This would be useful if 
> it would bypass the need to write/read to/from disk everytime the PNG 
> file changes.
>
In the absence of this being wrapped, you can just use Wx::Image and 
it's methods of you can Select it into a device context (eg 
Wx::MemoryDC) like this:

         my $mdc = Wx::MemoryDC->new();
         $mdc->SelectObject($frame->{bmp});         # Having stored your 
bitmap from before
         my $pen = Wx::Pen->new( $colourData, 3, wxSOLID);
         $mdc->SetPen( $pen );
         $mdc->SetBrush( wxTRANSPARENT_BRUSH );
         # Determine mouse courdinates
         my $x=$event->GetX();
         my $y=$event->GetY();
         # Draw circle round mouse event
         $mdc->DrawCircle( $x, $y, $r );
         $mdc->SelectObject(wxNullBitmap);                     # 
deselect the bitmap out of the DC
         $frame->{sbmp}->SetBitmap(frame->{bmp});

As you do in your linear panel meter.

Regards

Steve.