Tk_FindPhoto(3) Tk Library Procedures Tk_FindPhoto(3) 







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.








#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)










  
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.
    
    

    

  










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(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
  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.










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.










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










photo, image







  

    8.0
    Tk