getimage(3Tk)

NAME
     Tk_GetImage, Tk_RedrawImage, Tk_SizeOfImage, Tk_FreeImage - use an image
     in a widget

SYNOPSIS
     #include <tk.h>

     Tk_Image
     Tk_GetImage(interp, tkwin, name, changeProc, clientData)

     Tk_RedrawImage(image, imageX, imageY, width, height, drawable,
      drawableX, drawableY)

     Tk_SizeOfImage(image, widthPtr, heightPtr)

     Tk_FreeImage(image)

ARGUMENTS
     Tcl_Interp            *interp       (in)      Place to leave error
                                                   message.

     Tk_Window             tkwin         (in)      Window in which image will
                                                   be used.

     char                  *name         (in)      Name of image.

     Tk_ImageChangedProc   *changeProc   (in)      Procedure for Tk to invoke
                                                   whenever image content or
                                                   size changes.

     ClientData            clientData    (in)      One-word value for Tk to
                                                   pass to changeProc.

     Tk_Image              image                   Token for image instance;
                                                   must have been returned by
                                                   a previous call to
                                                   Tk_GetImage.

     int                   imageX        (in)      X-coordinate of upper-left
                                                   corner of region of image
                                                   to redisplay (measured in
                                                   pixels from the image's
                                                   upper-left corner).

     int                   imageY        (in)      Y-coordinate of upper-left
                                                   corner of region of image
                                                   to redisplay (measured in
                                                   pixels from the image's
                                                   upper-left corner).

     int                   width         ((in))    Width of region of image to
                                                   redisplay.

     int                   height        ((in))    Height of region of image
                                                   to redisplay.

     Drawable              drawable      (in)      Where to display image.
                                                   Must either be window
                                                   specified to Tk_GetImage or
                                                   a pixmap compatible with
                                                   that window.

     int                   drawableX     (in)      Where to display image in
                                                   drawable: this is the x-
                                                   coordinate in drawable
                                                   where x-coordinate imageX
                                                   of the image should be
                                                   displayed.

     int                   drawableY     (in)      Where to display image in
                                                   drawable: this is the y-
                                                   coordinate in drawable
                                                   where y-coordinate imageY
                                                   of the image should be
                                                   displayed.

     int                   widthPtr      (out)     Store width of image (in
                                                   pixels) here.

     int                   heightPtr     (out)     Store height of image (in
                                                   pixels) here.


DESCRIPTION
     These procedures are invoked by widgets that wish to display images.
     Tk_GetImage is invoked by a widget when it first decides to display an
     image.  name gives the name of the desired image and tkwin identifies the
     window where the image will be displayed.  Tk_GetImage looks up the image
     in the table of existing images and returns a token for a new instance of
     the image.  If the image doesn't exist then Tk_GetImage returns NULL and
     leaves an error message in interp->result.

     When a widget wishes to actually display an image it must call
     Tk_RedrawWidget, identifying the image (image), a region within the image
     to redisplay (imageX, imageY, width, and height), and a place to display
     the image (drawable, drawableX, and drawableY).  Tk will then invoke the
     appropriate image manager, which will display the requested portion of
     the image before returning.

     A widget can find out the dimensions of an image by calling
     Tk_SizeOfImage:  the width and height will be stored in the locations
     given by widthPtr and heightPtr, respectively.
     When a widget is finished with an image (e.g., the widget is being
     deleted or it is going to use a different image instead of the current
     one), it must call Tk_FreeImage to release the image instance.  The
     widget should never again use the image token after passing it to
     Tk_FreeImage.  There must be exactly one call to Tk_FreeImage for each
     call to Tk_GetImage.

     If the contents or size of an image changes, then any widgets using the
     image will need to find out about the changes so that they can redisplay
     themselves.  The changeProc and clientData arguments to Tk_GetImage are
     used for this purpose.  changeProc will be called by Tk whenever a change
     occurs in the image;  it must match the following prototype:
          typedef void Tk_ImageChangedProc(
               ClientData clientData,
               int x,
               int y,
               int width,
               int height,
               int imageWidth,
               int imageHeight);
     The clientData argument to changeProc is the same as the clientData
     argument to Tk_GetImage.  It is usually a pointer to the widget record
     for the widget or some other data structure managed by the widget.  The
     arguments x, y, width, and height identify a region within the image that
     must be redisplayed; they are specified in pixels measured from the
     upper-left corner of the image.  The arguments imageWidth and imageHeight
     give the image's (new) size.


SEE ALSO
     Tk_CreateImageType


KEYWORDS
     images, redisplay