Tk_CreatePhotoImageFormat(3)Tk (4.0) Tk_CreatePhotoImageFormat(3)
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NAME
Tk_CreatePhotoImageFormat - define new file format for photo
images
SYNOPSIS
#include <tk.h>
#include <tkPhoto.h>
Tk_CreatePhotoImageFormat(formatPtr)
ARGUMENTS
Tk_PhotoImageFormat *formatPtr (in) Structure that
defines the new
file format.
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DESCRIPTION
Tk_CreatePhotoImageFormat is invoked to define a new file
format for image data for use with photo images. The code
that implements an image file format is called an image file
format handler, or handler for short. The photo image code
maintains a list of handlers that can be used to read and
write data to or from a file. Some handlers may also
support reading image data from a string or converting image
data to a string format. The user can specify which handler
to use with the -format image configuration option or the
-format option to the read and write photo image
subcommands.
An image file format handler consists of a collection of
procedures plus a Tk_PhotoImageFormat structure, which
contains the name of the image file format and pointers to
six procedures provided by the handler to deal with files
and strings in this format. The Tk_PhotoImageFormat
structure contains the following fields:
typedef struct Tk_PhotoImageFormat {
char *name;
Tk_ImageFileMatchProc *fileMatchProc;
Tk_ImageStringMatchProc *stringMatchProc;
Tk_ImageFileReadProc *fileReadProc;
Tk_ImageStringReadProc *stringReadProc;
Tk_ImageFileWriteProc *fileWriteProc;
Tk_ImageStringWriteProc *stringWriteProc;
} Tk_PhotoImageFormat;
The handler need not provide implementations of all six
procedures. For example, the procedures that handle string
data would not be provided for a format in which the image
data are stored in binary, and could therefore contain null
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Tk_CreatePhotoImageFormat(3)Tk (4.0) Tk_CreatePhotoImageFormat(3)
characters. If any procedure is not implemented, the
corresponding pointer in the Tk_PhotoImageFormat structure
should be set to NULL. The handler must provide the
fileMatchProc procedure if it provides the fileReadProc
procedure, and the stringMatchProc procedure if it provides
the stringReadProc procedure.
NAME
formatPtr->name provides a name for the image type. Once
Tk_CreatePhotoImageFormat returns, this name may be used in
the -format photo image configuration and subcommand option.
The manual page for the photo image (photo(n)) describes how
image file formats are chosen based on their names and the
value given to the -format option.
FILEMATCHPROC
formatPtr->fileMatchProc provides the address of a procedure
for Tk to call when it is searching for an image file format
handler suitable for reading data in a given file.
formatPtr->fileMatchProc must match the following prototype:
typedef int Tk_ImageFileMatchProc(
Tcl_Channel chan,
char *fileName,
char *formatString,
int *widthPtr,
int *heightPtr);
The fileName argument is the name of the file containing the
image data, which is open for reading as chan. The
formatString argument contains the value given for the
-format option, or NULL if the option was not specified. If
the data in the file appears to be in the format supported
by this handler, the formatPtr->fileMatchProc procedure
should store the width and height of the image in *widthPtr
and *heightPtr respectively, and return 1. Otherwise it
should return 0.
STRINGMATCHPROC
formatPtr->stringMatchProc provides the address of a
procedure for Tk to call when it is searching for an image
file format handler for suitable for reading data from a
given string. formatPtr->stringMatchProc must match the
following prototype:
typedef int Tk_ImageStringMatchProc(
char *string,
char *formatString,
int *widthPtr,
int *heightPtr);
The string argument points to the string containing the
image data. The formatString argument contains the value
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Tk_CreatePhotoImageFormat(3)Tk (4.0) Tk_CreatePhotoImageFormat(3)
given for the -format option, or NULL if the option was not
specified. If the data in the string appears to be in the
format supported by this handler, the formatPtr-
>stringMatchProc procedure should store the width and height
of the image in *widthPtr and *heightPtr respectively, and
return 1. Otherwise it should return 0.
FILEREADPROC
formatPtr->fileReadProc provides the address of a procedure
for Tk to call to read data from an image file into a photo
image. formatPtr->fileReadProc must match the following
prototype:
typedef int Tk_ImageFileReadProc(
Tcl_Interp *interp,
Tcl_Channel chan,
char *fileName,
char *formatString,
PhotoHandle imageHandle,
int destX, int destY,
int width, int height,
int srcX, int srcY);
The interp argument is the interpreter in which the command
was invoked to read the image; it should be used for
reporting errors. The image data is in the file named
fileName, which is open for reading as chan. The
formatString argument contains the value given for the
-format option, or NULL if the option was not specified.
The image data in the file, or a subimage of it, is to be
read into the photo image identified by the handle
imageHandle. The subimage of the data in the file is of
dimensions width x height and has its top-left corner at
coordinates (srcX,srcY). It is to be stored in the photo
image with its top-left corner at coordinates (destX,destY)
using the Tk_PhotoPutBlock procedure. The return value is a
standard Tcl return value.
STRINGREADPROC
formatPtr->stringReadProc provides the address of a
procedure for Tk to call to read data from a string into a
photo image. formatPtr->stringReadProc must match the
following prototype:
typedef int Tk_ImageStringReadProc(
Tcl_Interp *interp,
char *string,
char *formatString,
PhotoHandle imageHandle,
int destX, int destY,
int width, int height,
int srcX, int srcY);
The interp argument is the interpreter in which the command
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Tk_CreatePhotoImageFormat(3)Tk (4.0) Tk_CreatePhotoImageFormat(3)
was invoked to read the image; it should be used for
reporting errors. The string argument points to the image
data in string form. The formatString argument contains the
value given for the -format option, or NULL if the option
was not specified. The image data in the string, or a
subimage of it, is to be read into the photo image
identified by the handle imageHandle. The subimage of the
data in the string is of dimensions width x height and has
its top-left corner at coordinates (srcX,srcY). It is to be
stored in the photo image with its top-left corner at
coordinates (destX,destY) using the Tk_PhotoPutBlock
procedure. The return value is a standard Tcl return value.
FILEWRITEPROC
formatPtr->fileWriteProc provides the address of a procedure
for Tk to call to write data from a photo image to a file.
formatPtr->fileWriteProc must match the following prototype:
typedef int Tk_ImageFileWriteProc(
Tcl_Interp *interp,
char *fileName,
char *formatString,
Tk_PhotoImageBlock *blockPtr);
The interp argument is the interpreter in which the command
was invoked to write the image; it should be used for
reporting errors. The image data to be written are in
memory and are described by the Tk_PhotoImageBlock structure
pointed to by blockPtr; see the manual page FindPhoto(3) for
details. The fileName argument points to the string giving
the name of the file in which to write the image data. The
formatString argument contains the value given for the
-format option, or NULL if the option was not specified.
The format string can contain extra characters after the
name of the format. If appropriate, the formatPtr-
>fileWriteProc procedure may interpret these characters to
specify further details about the image file. The return
value is a standard Tcl return value.
STRINGWRITEPROC
formatPtr->stringWriteProc provides the address of a
procedure for Tk to call to translate image data from a
photo image into a string. formatPtr->stringWriteProc must
match the following prototype:
typedef int Tk_ImageStringWriteProc(
Tcl_Interp *interp,
Tcl_DString *dataPtr,
char *formatString,
Tk_PhotoImageBlock *blockPtr);
The interp argument is the interpreter in which the command
was invoked to convert the image; it should be used for
reporting errors. The image data to be converted are in
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Tk_CreatePhotoImageFormat(3)Tk (4.0) Tk_CreatePhotoImageFormat(3)
memory and are described by the Tk_PhotoImageBlock structure
pointed to by blockPtr; see the manual page FindPhoto(3) for
details. The data for the string should be appended to the
dynamic string given by dataPtr. The formatString argument
contains the value given for the -format option, or NULL if
the option was not specified. The format string can contain
extra characters after the name of the format. If
appropriate, the formatPtr->stringWriteProc procedure may
interpret these characters to specify further details about
the image file. The return value is a standard Tcl return
value.
SEE ALSO
Tk_FindPhoto, Tk_PhotoPutBlock
KEYWORDS
photo image, image file
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