OverlayBitmap

The OverlayBitmap object is used to draw graphical elements like lines and text onto the video stream.

There are three possible locations where overlay objects may be inserted in the image stream:

Behind the device ( Device Path ): this overlay will appear in the display as well as in the sink (ring buffer, stream file)
In front of the display ( Display Path ): this overlay will appear in the display only
In front of the sink ( Sink Path ): this overlay will appear in the sink (ring buffer, stream file) only

Internally, the OverlayBitmap object uses a bitmap (HBITMAP) for drawing text and graphical elements on the video stream. Its size and color depth are dependent on the video format of the currently active video capture device and all frame filters that are inserted between the device and itself. Therefore, the internal bitmap is destroyed and recreated, if:

the device's video format is changed,
the sink's video format is changed because it may require automatic color space conversion somewhere in front of the overlay,
frame filters are inserted/removed between the device and the overlay
parameters of a frame filter that are inserted between the device and the overlay are altered in a way that the video format of the image stream is changed.

The color format of the overlay is determined by the objects that are located in front and behind it in the image stream. In addition, the color format can be forced to monochrome or RGB with a call to OverlayBitmap::setColorMode.

The functionality of the OverlayBitmap object is not available and the method OverlayBitmap::canRender returns false in two cases:

the sink's color format is set to YUV
the filter that is inserted just behind the overlay requires YUV as the input format

Pointers to instances of OverlayBitmap objects can be retrieved with a call to the Grabber's method Grabber::getOverlay.

Information

    Header File: tisudshl.h
    Namespace: DShowlib
    Introduced in version 1.x

Methods

	Method		Description


	beginPaint		Prepares the overlay bitmap for graphic operations.

	canRender		Returns whether the framework is able to render the overly on the video stream.

	drawFrameEllipse		Draws the frame of an ellipse on the live video.

	drawFrameRect		Draws the frame of a rectangle on the live video.

	drawLine		Draws a line on the live video.

	drawSolidEllipse		Draws a solid ellipse on the live video.

	drawSolidRect		Draws a solid rectangle on the live video.

	drawText		Draws a text on the live video.

	endPaint		Releases the overlay bitmap from the internal device context.

	fill		Fills the entire overlay bitmap with the specified color.

	getColorMode		Returns the currently selected color mode of this OverlayBitmap.

	getColorformat		Returns the current color format used for the overlay.

	getDC		Returns the device context.

	getDropOutColor		Returns the currently used dropout color.

	getEnable		Returns whether the overlay is visible on the live video stream.

	getFlipVertical		Returns whether the overlay bitmap is displayed vertically flipped on the video.

	getFont		Retrieves a pointer to an IFont COM font object pointer.

	getFontBKColor		Returns the background color for text drawings.

	getFontTransparent		Returns the background mode for text drawings.

	getFrameType		Returns a FrameTypeInfo object describing the current format of this OverlayBitmap.

	getHeight		Returns the height of the OverlayBitmap.

	getPathPosition		Returns the path position of this OverlayBitmap.

	getWidth		Returns the width of the OverlayBitmap.

	setColorMode		Set the color mode of this OverlayBitmap. The color mode determines, whether the overlay bitmap is painted in color or grayscale. The images provided by the video capture device are converted into the selected format before drawing the overlay.

	setDropOutColor		Sets the dropout color.

	setEnable		Enables or disables the display of the overlay bitmap on the live video.

	setFlipVertical		Enables or disables the vertical flip of the overlay bitmap.

	setFont		Sets the OverlayBitmaps object font to the specified font.

	setFontBKColor		Sets the background color for drawing text to the specified color value, or to the nearest physical color if the device cannot represent the specified color value.

	setFontTransparent		Sets the background mode for text drawings.

Enumerations

	Enumeration		Description


	tOVBColorMode		The members of this enumeration are used to set the color format of the OverlayBitmap, using setColorMode.

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