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 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 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 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