The MontiVision GDI Overlay filter overlays a GDI surface onto the video stream. Either a colour for the transparent background is specified or a constant alpha value for the whole image is used. If a background colour is specified, every pixel with this colour is set as transparent. If a constant alpha value is used, the output video is calculated as follows: Output = Input * Alpha + Overlay * (255-Alpha).
This MontiVision DirectShow Filter is used in combination with the MontiVision Smart Control in the LiveDraw Sample Application.
| File: | GDIOverlay.ax |
| CLSID: | CLSID_MVGDIOverlay |
Interface
Supported COM Events
The filter supports following events through the IMVFilterEvents interface. Look at the filter events page for more information.
| Event |
Value |
Description |
| MV_ALGORITHM_START_EVENT |
0 |
A filter starts processing a video frame or sample. |
| MV_ALGORITHM_END_EVENT |
1 |
A filter finishes processing a video frame or sample. |
MV GDI Overlay Property Page
Uses the IMVGDIOverlay configuration interface.
| Transparent background | A transparent background is used. Every pixel with a specified colour is set as transparent. |
| Background colour | The currently selected background colour. |
| Constant image alpha | A constant alpha value is used for every pixel of the image. |
| Video alpha value |
Output pixel value = Input pixel value
* Alpha
+ |
| Don't erase DC surface on GetDC() | This flag specifies whether the DC surface is deleted on every call to GetDC(). |
| Erase DC surface()! | Immediately erases the DC surface. |