fast overlay display

[Didier]

Hello,
i am reactiving this subject
[Link to the old forum deleted]

because i didnt have any feedback.

When we do have a scene, or lets say a background zoomable .jpg picture, and we want to add dynamically element on this map (icons, or small jpg), do we have to redraw the whole scene+objects, or is there a way of recomputing only the changes ?

problem is that when backround picture is big, redisplaying the whole stuff leads to clipping,

Thanks

[Loïc]

Hi,

If I understand what you want to do is to dispay a large image file with the gdviewer object and to display over it other smallest pictures/images ?


You can do that easily:

- Catch the Displayed() event of the GdViewer object.
- Use a cGdPicture object to draw image on HDC: DisplayImageOnHDC() method

vb6 sample code:

Code: Select all

Dim oGdPicture As New GdpicturePro.cGdPicture
Dim nIcoHandle As Long


Private Sub Command1_Click()
oGdViewer.DisplayFromFile (Text2.Text)
End Sub

Private Sub Form_Load()
  oGdViewer.SetLicenceNumber ("0012345678910111213141516") 'Demo code version
  nIcoHandle = oGdPicture.CreateImageFromFile("icon.ico")
End Sub

Private Sub oGdViewer_Displayed()
  Call oGdPicture.SetNativeImage(nIcoHandle)
  Call oGdPicture.DisplayImageOnHDC(oGdViewer.hDC, 1, 1, 100, 100)
End Sub

You can download this demo project from here:
https://www.gdpicture.com/ressources/support/overlay.zip


Best regards,

Loïc Carrère

[Didier]

hi Loic thanks for replying,

if i do the OnHDC, will the icon be zoomed in zoomed out as well ?!


Didier

[Loïc]

Hi,

if i do the OnHDC, will the icon be zoomed in zoomed out as well ?!

I don't understand the question

Loïc

[Didier]

i mean, if i display an ico using the DisplayImageOnHDC(),
then zoom in the whole scene using the mouse, will the ico be zoomed in as well ?

actually maybe if i capture the ZoomChanged event and call gdObject.Resize() to match the new zoom it will do it ?

i need to place lot of object on the map and move them around, i need them to be zoomable (to follow the main map scale)

[Didier]

actually, how can i remove the gdobject from the viewver once it has beeen placed using DisplayOnHDC() ??

[Loïc]

actually, how can i remove the gdobject from the viewver once it has beeen placed using DisplayOnHDC() ??

You have just to call the Refresh() method of the gdviewer control and don't call thes lines:

Code: Select all

Call oGdPicture.SetNativeImage(nIcoHandle) 
 Call oGdPicture.DisplayImageOnHDC(oGdViewer.hDC, 1, 1, 100, 100) 

You can do something like that:

Code: Select all

Dim bWantDisplayItems  As Boolean 'Public Var

bWantDisplayItems = False
Call oGdViewer.Refresh()
bWantDisplayItems = True


Private Sub oGdViewer_Displayed() 
  If bWantDisplayItems Then
     Call oGdPicture.SetNativeImage(nIcoHandle) 
     Call oGdPicture.DisplayImageOnHDC(oGdViewer.hDC, 1, 1, 100, 100) 
  End If
End Sub 

[Didier]

sorry i am a bit lost.

what the refresh does ??! in the doc there is no explanation,
what is the diff between refresh redraw ?

if i do refresh will it be faster than redraw?

[oneuser]

Hi,

Sorry, you are right.

You have to call the Redraw() method and not the Refresh().

Loïc