Tk_FindPhoto(3) Tk Library Procedures Tk_FindPhoto(3)
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NAME
Tk_FindPhoto, Tk_PhotoPutBlock, Tk_PhotoPutZoomedBlock, Tk_PhotoGetImage, Tk_PhotoBlank, Tk_PhotoEx-pand, Tk_PhotoExpand,
pand, Tk_PhotoGetSize, Tk_PhotoSetSize - manipulate the image data stored in a photo image.
SYNOPSIS
#include <tk.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 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 direc-tion direction
tion to pixels being written to the photo image.
int zoomY (in) Specifies the zoom factor to be applied in the Y direc-tion direction
tion to pixels being written to the photo image.
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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(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 contain-ing containing
ing 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_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 corre-sponding corresponding
sponding procedure in the old photo widget.
Tk_PhotoBlank blanks the entire area of the photo image. Blank areas of a photo image are transpar-ent. transparent.
ent.
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 subse-quent subsequent
quent calls to Tk_PhotoPutBlock, Tk_PhotoPutZoomedBlock 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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