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#1 Posted : Friday, August 4, 2006 11:09:48 AM(UTC)

pmelies  
pmelies

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Posts: 3


We have an application that sits on a tablet PC with a digital camera using LEAD v 12.0.  The application allows a user to snap photos at will.  It currently uses the LEADCapture and Main controls to do this.  We now have a requirement to provide a digital zoom functionality for the user through our application and it looks like LEAD v 12.0 can't do this.  So I've downloaded the evaluation copy of the latest software.

The camera itself apparently doesn't provide zoom capabilities since the CameraControl property of the ltmmCaptureCtrl1 control returns Nothing.

I thought I could simulate a digital zoom by applying filters, perhaps first a Crop and then a Resize.  However, I'm having trouble using the filters.  At one point I was getting "The graph must be stopped" messages when trying to apply new filter property settings.  I'm not sure what a "graph" is.

Can anyone tell me if this is possible, and if so, how do I properly use the filters to do this?

 

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#2 Posted : Monday, August 7, 2006 3:35:11 AM(UTC)
Maen Hasan

Groups: Registered, Tech Support
Posts: 1,328

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Hello,

In DirectShow, which LEADTOOLS Multimedia 15 is based on, any multimedia functionality is performed by connecting 2 or more 'filters' in what's known as a filter graph. For example, a very simple graph consists of a Video Source filter (such as camera capture driver) and a preview window (Video renderer filter). It will look like this:
(Video Source) -> (Renderer)

The toolkit internally builds advanced graphs using needed filters to perform tasks, such as capturing, playing and converting.

Begin by using one of our Capture demos, which have menu items to insert processing filters, and manipulating their property pages. If you can't set the properties of any filter, disable the preview and try again.

Thanks,
Maen Badwan
LEADTOOLS Technical Support
 
#3 Posted : Tuesday, August 8, 2006 9:04:52 AM(UTC)

pmelies  
pmelies

Groups: Registered
Posts: 3


Can you tell me what demo has the filter code?  The VB6 demos I have don't have it.

What are the defaults of the Crop filter?  Simply by adding the Crop filter to the SelectedVideoProcessors collection of the capture control it appears that the video is being cropped.

Also, when applying the filter the preview goes black.  Is this while the graph is being stopped to insert the new processing filter?  If so, is it possible to apply the filter at the beginning of the application and then change its properties at runtime without the preview going black?  I ask because when I call the ResetToDefaults method on the LMVCrop method the application errors and shuts down, even when it's surrounded by a "On Error Goto X" error handler.

As for the Resize filter, I'm not sure I really need.  It appears I can accomplish the same thing by setting the capture control's VideoWindowSizeMode mode to "Fit".

 
#4 Posted : Thursday, August 10, 2006 6:03:46 AM(UTC)
Maen Hasan

Groups: Registered, Tech Support
Posts: 1,328

Was thanked: 1 time(s) in 1 post(s)

Hello,

About the filters, you can check the effect of the filters by using the "VB Multimedia Capture" demo as follows:
- Run the demo.
- Select menu "Options"\"Video Processors" (Video Processors dialog appears).
- Within the dialog, click the "Insert Before" button and then select the "LEAD Video Crop filter" then Click OK within the open dialogs.
- check the filter settings and effect.

The default values of the crop filter (as mentioned in the crop filter dialog) are (0, 0, 100, 100).

However, to make sure that you are using the filters correctly in your code, please refer to the LEADTOOLS MM documentation and read the following topics and tutorials:
- Access the Interface of Filters (Visual Basic).
- Programmatically Inserting a Processor Filter (Visual Basic).
- Directly Access the DirectShow Objects (Visual Basic).

Thanks,
Maen Badwan
LEADTOOLS Technical Support
 
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