Sequences of Images
You can display a sequence of bitmaps with the same dimensions and formats by
using the
DrawDibDraw function with the
DrawDibBegin function.
DrawDibBegin improves the efficiency of
DrawDibDraw by preparing the DrawDib DC for drawing.
Note If your application does not use
DrawDibBegin,
DrawDibDraw implicitly executes it prior to drawing. If your application uses
DrawDibBegin prior to
DrawDibDraw,
DrawDibDraw does not have to process the function and wait for it to complete.
The
DrawDibBegin function provides
DrawDibDraw with the DrawDib DC, the DC handle, the address of the
BITMAPINFOHEADER structure, and the source and destination rectangle dimensions. When you
display a sequence of bitmaps,
DrawDibDraw checks the values of these items for each image in the sequence. If
DrawDibDraw detects changes to any of these items, it implicitly calls
DrawDibBegin again to adjust the DrawDib DC settings.
After using
DrawDibBegin, you can draw the image sequence by using
DrawDibDraw and specifying one or more flags as appropriate. Specify the DDF_SAME_HDC
flag as long as the DC handle has not changed. Specify the DDF_SAME_DRAW flag when
the following parameters for
DrawDibDraw have not changed: the address of the
BITMAPINFOHEADER structure and the source and destination rectangle dimensions.
You can update the flags set with
DrawDibBegin by using the
DrawDibEnd function followed by another call to
DrawDibBegin. Then use
DrawDibEnd to clear the DrawDib DC of its current flags and settings. The subsequent
call to
DrawDibBegin reinitializes the DrawDib DC with the appropriate flags and settings.
Alternatively, you can update the flags for a DrawDib DC by using
DrawDibBegin without
DrawDibEnd. To do this, you must change at least one of the following settings
concurrently with the flags: the address of the
BITMAPINFOHEADER structure, or the source or destination rectangle dimensions.
You can increase the efficiency of
DrawDibDraw for data-streaming operations that use compressed images, such as playing a
video clip, by using the
DrawDibStart and
DrawDibStop functions. The
DrawDibStart function prepares the DrawDib DC to receive a stream of images by sending a
message to the video compression manager (VCM). When streaming has ended,
DrawDibStop sends a message to VCM indicating that it can release resources it allocated
for the data-streaming operation. For more information about VCM, see
Video Compression Manager.
Note You must specify the width and height of the source and destination
rectangles in your application. However, you do not need to specify the origins of the
rectangles. Your application can redefine the origins in
DrawDibDraw to use different portions of the image or to update different portions of the
display.
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