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Tk_FindPhoto(3)		     Tk Library Procedures	       Tk_FindPhoto(3)

______________________________________________________________________________

NAME
       Tk_FindPhoto,  Tk_PhotoPutBlock, Tk_PhotoPutZoomedBlock, Tk_PhotoGetIm-
       age, Tk_PhotoBlank, Tk_PhotoExpand, Tk_PhotoGetSize, Tk_PhotoSetSize  -
       manipulate the image data stored in a photo image.

SYNOPSIS
       #include <tk.h>
       #include <tkPhoto.h>

       Tk_PhotoHandle
       Tk_FindPhoto(interp, imageName)					       |

       void
       Tk_PhotoPutBlock(handle, blockPtr, x, y, width, height, compRule)

       void
       Tk_PhotoPutZoomedBlock(handle, blockPtr, x, y, width, height,zoomX, zoomY, subsampleX, subsampleY, compRule)

       int
       Tk_PhotoGetImage(handle, blockPtr)

       void
       Tk_PhotoBlank(handle)

       void
       Tk_PhotoExpand(handle, width, height)

       void
       Tk_PhotoGetSize(handle, widthPtr, heightPtr)

       void
       Tk_PhotoSetSize(handle, width, height)

ARGUMENTS
       Tcl_Interp	    *interp	  (in)	    Interpreter in which image |
						    was created.

       CONST char	    *imageName	  (in)	    Name of the photo image.

       Tk_PhotoHandle	    handle	  (in)	    Opaque handle  identifying
						    the	  photo	 image	to  be
						    affected.

       Tk_PhotoImageBlock   *blockPtr	  (in)	    Specifies the address  and
						    storage  layout  of	 image
						    data.

       int		    x		  (in)	    Specifies the X coordinate
						    where  the top-left corner
						    of	the  block  is	to  be
						    placed within the image.

       int		    y		  (in)	    Specifies the Y coordinate
						    where the top-left	corner
						    of	the  block  is	to  be
						    placed within the image.

       int		    width	  (in)	    Specifies the width of the
						    image  area to be affected
						    (for Tk_PhotoPutBlock)  or
						    the	 desired  image	 width
						    (for  Tk_PhotoExpand   and
						    Tk_PhotoSetSize).	       |

       int		    com-					       |
       pRule	  (in)				       |		       |
						    Specifies the  compositing |
						    rule  used	when combining |
						    transparent	 pixels	 in  a |
						    block of data with a photo |
						    image.   Must  be  one  of |
						    TK_PHOTO_COMPOSITE_OVERLAY |
						    (which puts the  block  of |
						    data  over	the top of the |
						    existing photo image, with |
						    the	   previous   contents |
						    showing  through  in   the |
						    transparent	   bits)    or |
						    TK_PHOTO_COMPOSITE_SET     |
						    (which discards the exist- |
						    ing photo  image  contents |
						    in	the  rectangle covered |
						    by the data block.)

       int		    height	  (in)	    Specifies  the  height  of
						    the	  image	  area	to  be
						    affected (for Tk_PhotoPut-
						    Block)   or	  the  desired
						    image height (for  Tk_Pho-
						    toExpand  and Tk_PhotoSet-
						    Size).

       int		    *widthPtr	  (out)	    Pointer  to	 location   in
						    which  to  store the image
						    width.

       int		    *heightPtr	  (out)	    Pointer  to	 location   in
						    which  to  store the image
						    height.

       int		    subsampleX	  (in)	    Specifies the  subsampling
						    factor  in the X direction
						    for input image data.

       int		    subsampleY	  (in)	    Specifies the  subsampling
						    factor  in the Y direction
						    for input image data.

       int		    zoomX	  (in)	    Specifies the zoom	factor
						    to	be  applied  in	 the X
						    direction to pixels	 being
						    written   to   the	 photo
						    image.

       int		    zoomY	  (in)	    Specifies the zoom	factor
						    to	be  applied  in	 the Y
						    direction to pixels	 being
						    written   to   the	 photo
						    image.
_________________________________________________________________

DESCRIPTION
       Tk_FindPhoto returns an opaque handle that is used to identify  a  par-
       ticular photo image to the other procedures.  The parameter is the name
       of the image, that is, the name specified to  the  image	 create	 photo
       command, or assigned by that command if no name was specified.

       Tk_PhotoPutBlock	 is  used  to  supply  blocks of image data to be dis-
       played.	The call affects an area of the image of size width  x	height
       pixels,	with  its top-left corner at coordinates (x,y).	 All of width,
       height, x, and y must be non-negative.  If part of this area lies  out-
       side  the  current  bounds  of the image, the image will be expanded to
       include the area, unless the user has specified an explicit image  size
       with  the  -width  and/or  -height  widget  configuration  options (see
       photo(n)); in that case the area	 is  silently  clipped	to  the	 image
       boundaries.

       The  block  parameter  is  a pointer to a Tk_PhotoImageBlock structure,
       defined as follows:
	      typedef struct {
		unsigned char *pixelPtr;
		int width;
		int height;
		int pitch;
		int pixelSize;
		int offset[4];
	      } Tk_PhotoImageBlock;
       The pixelPtr field points to the first pixel,  that  is,	 the  top-left
       pixel in the block.  The width and height fields specify the dimensions
       of the block of pixels.	The pixelSize field specifies the address dif-
       ference	between two horizontally adjacent pixels.  Often it is 3 or 4,
       but it can have any value.  The pitch field specifies the address  dif-
       ference	between two vertically adjacent pixels.	 The offset array con-
       tains the offsets from the address of a pixel to the addresses  of  the
       bytes  containing  the red, green, blue and alpha (transparency) compo-
       nents.  These are normally 0, 1, 2 and 3, but can  have	other  values,
       e.g.,  for  images  that	 are  stored  as  separate red, green and blue
       planes.

       The compRule parameter to Tk_PhotoPutBlock specifies a compositing rule |
       that  says what to do with transparent pixels.  The value TK_PHOTO_COM- |
       POSITE_OVERLAY says that the  previous  contents	 of  the  photo	 image |
       should show through, and the value TK_PHOTO_COMPOSITE_SET says that the |
       previous contents of the photo image should be completely ignored,  and |
       the  values  from the block be copied directly across.  The behavior in |
       Tk8.3 and earlier was equivalent to  having  TK_PHOTO_COMPOSITE_OVERLAY |
       as a compositing rule.

       The value given for the width and height parameters to Tk_PhotoPutBlock
       do not have to correspond to the values specified in  block.   If  they
       are  smaller, Tk_PhotoPutBlock extracts a sub-block from the image data
       supplied.  If they are larger, the data	given  are  replicated	(in  a
       tiled  fashion)	to fill the specified area.  These rules operate inde-
       pendently in the horizontal and vertical directions.

       Tk_PhotoPutZoomedBlock works  like  Tk_PhotoPutBlock  except  that  the
       image  can be reduced or enlarged for display.  The subsampleX and sub-
       sampleY parameters allow the size of the image to be reduced by subsam-
       pling.	Tk_PhotoPutZoomedBlock	will  use  only	 pixels from the input
       image whose X coordinates are multiples	of  subsampleX,	 and  whose  Y
       coordinates  are	 multiples  of	subsampleY.   For example, an image of
       512x512 pixels can be reduced to 256x256 by setting subsampleX and sub-
       sampleY to 2.

       The  zoomX and zoomY parameters allow the image to be enlarged by pixel
       replication.  Each pixel of the (possibly subsampled) input image  will
       be  written  to	a block zoomX pixels wide and zoomY pixels high of the
       displayed image.	 Subsampling and zooming can be used together for spe-
       cial effects.

       Tk_PhotoGetImage can be used to retrieve image data from a photo image.
       Tk_PhotoGetImage fills in the structure	pointed	 to  by	 the  blockPtr
       parameter with values that describe the address and layout of the image
       data that the photo image has stored internally.	 The values are	 valid
       until  the image is destroyed or its size is changed.  Tk_PhotoGetImage
       returns 1 for compatibility with the corresponding procedure in the old
       photo widget.

       Tk_PhotoBlank  blanks  the entire area of the photo image.  Blank areas
       of a photo image are transparent.

       Tk_PhotoExpand requests that the widget's image be expanded  to	be  at
       least  width  x	height	pixels	in  size.  The width and/or height are
       unchanged if the user has specified an explicit image width  or	height
       with the -width and/or -height configuration options, respectively.  If
       the image data are being supplied in many  small	 blocks,  it  is  more
       efficient  to  use  Tk_PhotoExpand  or Tk_PhotoSetSize at the beginning
       rather than allowing the image to expand in many	 small	increments  as
       image blocks are supplied.

       Tk_PhotoSetSize	specifies  the	size  of the image, as if the user had
       specified the given width and height values to the -width  and  -height
       configuration  options.	 A  value of zero for width or height does not
       change the image's width or height, but allows the width or  height  to
       be  changed by subsequent calls to Tk_PhotoPutBlock, Tk_PhotoPutZoomed-
       Block or Tk_PhotoExpand.

       Tk_PhotoGetSize returns the dimensions of the image  in	*widthPtr  and
       *heightPtr.

PORTABILITY
       In  Tk 8.3 and earlier, Tk_PhotoPutBlock and Tk_PhotoPutZoomedBlock had |
       different signatures. If you want to compile code  that	uses  the  old |
       interface  against  8.4 without updating your code, compile it with the |
       flag  -DUSE_COMPOSITELESS_PHOTO_PUT_BLOCK.   Code  linked  using	 Stubs |
       against older versions of Tk will continue to work.

CREDITS
       The  code  for  the  photo  image type was developed by Paul Mackerras,
       based on his earlier photo widget code.

KEYWORDS
       photo, image

Tk				      8.0		       Tk_FindPhoto(3)
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