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
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.
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.
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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