Providing
Controls for Cropping and Stretching Images
MCIWnd allows
you to crop and stretch images of a video clip. To understand these features,
you need to understand the relationships between frame size, source
rectangle, destination rectangle, and playback area.
A video clip
consists of several frames, each containing one image. The frame size of a
video clip is the size of the image in the current frame. Typically, a video
clip has one frame size because all the images in the clip are the same size.
The source
rectangle is a rectangular area that overlays the frames of a video
clip. The source rectangle defines the portion of each frame that is displayed
during playback. When a video clip is loaded with MCIWnd, the source rectangle
is initialized with the same dimensions and position as the initial frame of
the video clip.
The
destination rectangle is a rectangular area that defines a virtual
playback window. The destination rectangle receives the image data from the
source rectangle for each frame of the video clip. When the source and
destination rectangle dimensions are different, MCIWnd adjusts the image data
horizontally and vertically as needed to fill the destination rectangle. When a
video clip is loaded with MCIWnd, the destination rectangle is initialized with
the same dimensions and position as the initial frame of the video clip.
The playback
area is the portion of an MCIWnd window an application uses to display
the video clip. The playback area is the client area of an MCIWnd window or the
portion of the client area that excludes the MCIWnd toolbar. When a video clip
is loaded with MCIWnd, the playback area is initialized with the same
dimensions and position as the initial frame of the video clip.
You can crop
a video clip by using the MCIWndGetSource and MCIWndPutSource macros to alter the source rectangle.
Cropping an image determines only which portion of the frames are displayed
during playback; it does not alter the content of the file being played. Before
you crop an image, you can retrieve the current size of the source rectangle by
using MCIWndGetSource. After the new size and location of the source
rectangle are calculated, you can set the cropping boundaries of the source
rectangle by using MCIWndPutSource.
You can stretch
a video clip by using the MCIWndGetDest and MCIWndPutDest macros to alter the
destination rectangle. When you stretch a video clip, you lengthen or shorten
the frame size of a video clip vertically, horizontally, or in both directions.
Before you stretch an image, you can retrieve the current size and location of
the destination rectangle by using MCIWndGetDest. The MCIWndPutDest
macro allows you to redefine the destination rectangle. Stretching can distort
the image during playback, but it does not alter the content of the file being
played.
If the size
of the destination rectangle becomes larger than the playback area, you can
specify which portion of the playback area will display the video clip by using
MCIWndPutDest.
Note The MCIWndPutDest macro does not change the
size of the playback area. To stretch the MCIWnd window along with the
destination rectangle, you need to know the current size of the MCIWnd window
and issue new window dimensions based on the destination rectangle. You can
retrieve the MCIWnd window dimensions by using the GetWindowRect function and resize the
MCIWnd window by using the SetWindowPos function.