Tk_GetImage(3Tk)					      Tk_GetImage(3Tk)

NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

     #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    [Toc]    [Back]

     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).






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Tk_GetImage(3Tk)					      Tk_GetImage(3Tk)



     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 xcoordinate
 in drawable
						   where x-coordinate imageX
						   of the image	should be
						   displayed.

     int		   drawableY	 (in)	   Where to display image in
						   drawable: this is the ycoordinate
 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    [Toc]    [Back]

     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.



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Tk_GetImage(3Tk)					      Tk_GetImage(3Tk)



     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    [Toc]    [Back]

     Tk_CreateImageType

KEYWORDS    [Toc]    [Back]

     images, redisplay


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