Tk_FindPhoto(3)              Tk Library Procedures             Tk_FindPhoto(3)


       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.

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

       Tk_FindPhoto(interp, imageName)                                         |

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

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

       Tk_PhotoGetImage(handle, blockPtr)


       Tk_PhotoExpand(handle, width, height)

       Tk_PhotoGetSize(handle, widthPtr, heightPtr)

       Tk_PhotoSetSize(handle, width, height)

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

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

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

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

       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

       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-

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

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

       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

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

       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

       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

       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

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

       photo, image

Tk                                    8.0                      Tk_FindPhoto(3)