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Tk_GetImage(3)                              Tk Library Procedures                             Tk_GetImage(3)



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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.

       const 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 (in)                           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 upperleft
                                                     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 upperleft
                                                     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 speci-fied specified
                                                     fied to Tk_GetImage or a pixmap  compatible  with  that
                                                     window.

       int drawableX (in)                            Where to display image in drawable: this is the x-coor-dinate x-coordinate
                                                     dinate 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-coor-dinate y-coordinate
                                                     dinate 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.
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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 does not  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_RedrawImage, 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 redis-played; redisplayed;
       played; 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



Tk                                                   4.0                                      Tk_GetImage(3)