Tk_FindPhoto(3) Tk (8.0) Tk_FindPhoto(3)
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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>
#include <tkPhoto.h>
Tk_PhotoHandle
Tk_FindPhoto(interp, imageName) |
void
Tk_PhotoPutBlock(handle, blockPtr, x, y, width, height)
void
Tk_PhotoPutZoomedBlock(handle, blockPtr, x, y, width, height,zoomX, zoomY, subsampleX, subsampleY)
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.
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
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Tk_FindPhoto(3) Tk (8.0) Tk_FindPhoto(3)
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 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.
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Tk_FindPhoto(3) Tk (8.0) Tk_FindPhoto(3)
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.
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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
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Tk_FindPhoto(3) Tk (8.0) Tk_FindPhoto(3)
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[3];
} 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 and blue components. These are normally 0, 1 and 2,
but can have other values, e.g., for images that are stored
as separate red, green and blue planes.
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.
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Tk_FindPhoto(3) Tk (8.0) Tk_FindPhoto(3)
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_PhotoPutZoomedBlock
or Tk_PhotoExpand.
Tk_PhotoGetSize returns the dimensions of the image in
*widthPtr and *heightPtr.
CREDITS
The code for the photo image type was developed by Paul
Mackerras, based on his earlier photo widget code.
KEYWORDS
photo, image
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