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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 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 win-
						     dow 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-coordi-
						     nate  imageX  of  the  image  should be dis-
						     played.

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

       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_GetIm-
       age.

       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_GetIm-
       age.   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

Tk					       4.0				   Tk_GetImage(3)
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