Provided by: tk8.5-doc_8.5.11-1_all bug

NAME

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

SYNOPSIS

       #include <tk.h>

       Tk_PhotoHandle
       Tk_FindPhoto(interp, imageName)

       int                                                                                        │
       Tk_PhotoPutBlock(interp, handle, blockPtr, x, y, width, height,compRule)                   │

       int                                                                                        │
       Tk_PhotoPutZoomedBlock(interp, handle, blockPtr, x, y, width, height,zoomX, zoomY, subsampleX, subsampleY, compRule)│

       int
       Tk_PhotoGetImage(handle, blockPtr)

       void
       Tk_PhotoBlank(handle)

       int                                                                                        │
       Tk_PhotoExpand(interp, handle, width, height)                                              │

       void
       Tk_PhotoGetSize(handle, widthPtr, heightPtr)

       int                                                                                        │
       Tk_PhotoSetSize(interp. handle, width, height)                                             │

ARGUMENTS

       Tcl_Interp *interp (in)                      Interpreter in which image was created and in
                                                    which error reporting is to be done.

       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 compRule (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
                                                    existing   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_PhotoPutBlock)   or  the
                                                    desired image height (for Tk_PhotoExpand  and
                                                    Tk_PhotoSetSize).

       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 particular 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 displayed.  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 outside 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(3tk)); 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 difference between two horizontally adjacent pixels.  Often it
       is 3 or 4, but it can have any value.  The pitch field specifies  the  address  difference
       between  two  vertically  adjacent pixels.  The offset array contains the offsets from the
       address of a pixel to the addresses of the bytes containing the red, green, blue and alpha
       (transparency)  components.   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_COMPOSITE_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
       independently in the horizontal and vertical directions.

       Tk_PhotoPutBlock  normally  returns TCL_OK, though if it cannot allocate sufficient memory │
       to hold the resulting image, TCL_ERROR is returned instead and, if the interp argument  is │
       non-NULL, an error message is placed in the interpreter's result.

       Tk_PhotoPutZoomedBlock works like Tk_PhotoPutBlock except that the image can be reduced or
       enlarged for display.  The subsampleX and subsampleY parameters  allow  the  size  of  the
       image  to be reduced by subsampling.  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 subsampleY 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 special 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_PhotoExpand  normally returns TCL_OK, though if it cannot allocate sufficient memory to │
       hold the resulting image, TCL_ERROR is returned instead and, if  the  interp  argument  is │
       non-NULL, an error message is placed in the interpreter's result.

       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_PhotoPutZoomedBlock  or
       Tk_PhotoExpand.

       Tk_PhotoSetSize normally returns TCL_OK, though if it cannot allocate sufficient memory to │
       hold the resulting image, TCL_ERROR is returned instead and, if  the  interp  argument  is │
       non-NULL, an error message is placed in the interpreter's result.

       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.

       In Tk 8.4, Tk_PhotoPutBlock, Tk_PhotoPutZoomedBlock,  Tk_PhotoExpand  and  Tk_PhotoSetSize │
       did  not  take  an  interp argument or return any result code.  If insufficient memory was │
       available for an image, Tk would panic.  This behaviour is still supported if you  compile │
       your  extension  with the additional flag -DUSE_PANIC_ON_PHOTO_ALLOC_FAILURE.  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