Tk_CreatePhotoImageFormat(3Tk) Tk_CreatePhotoImageFormat(3Tk)
Tk_CreatePhotoImageFormat - define new file format for photo images
#include <tk.h>
#include <tkPhoto.h>
Tk_CreatePhotoImageFormat(formatPtr)
Tk_PhotoImageFormat *formatPtr (in) Structure that defines the
new file format.
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 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.
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Tk_CreatePhotoImageFormat(3Tk) Tk_CreatePhotoImageFormat(3Tk)
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.
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(
FILE *f,
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 f. 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.
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 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.
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(
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Tk_CreatePhotoImageFormat(3Tk) Tk_CreatePhotoImageFormat(3Tk)
Tcl_Interp *interp,
FILE *f,
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 f. 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.
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 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.
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,
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Tk_CreatePhotoImageFormat(3Tk) Tk_CreatePhotoImageFormat(3Tk)
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.
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 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.
Tk_FindPhoto, Tk_PhotoPutBlock
photo image, image file
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