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Tk_CreatePhotoImageForTktLibrary ProcTk_CreatePhotoImageFormat(3)

_________________________________________________________________

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.
_________________________________________________________________

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 con-
       verting image data to a string format.  The user can spec-
       ify which handler to use with the -format image configura-
       tion 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

Tk			       4.0				1

Tk_CreatePhotoImageForTktLibrary ProcTk_CreatePhotoImageFormat(3)

       implemented,  the corresponding pointer in the Tk_PhotoIm-
       ageFormat structure should be set to  NULL.   The  handler
       must  provide  the  fileMatchProc procedure if it provides
       the fileReadProc procedure, and the stringMatchProc proce-
       dure 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  proce-
       dure 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 proto-
       type:
	      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 for-
       matString argument contains the value given for the  -for-
       mat  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  *width-
       Ptr  and *heightPtr respectively, and return 1.	Otherwise
       it should return 0.

STRINGMATCHPROC
       formatPtr->stringMatchProc provides the address of a  pro-
       cedure  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

Tk			       4.0				2

Tk_CreatePhotoImageForTktLibrary ProcTk_CreatePhotoImageFormat(3)

       the  format  supported	by   this   handler,   the   for-
       matPtr->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  proce-
       dure for Tk to call to read data from an image file into a
       photo image.  formatPtr->fileReadProc must match the  fol-
       lowing prototype:
	      typedef int Tk_ImageFileReadProc(
		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 com-
       mand 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  format-
       String  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 stan-
       dard Tcl return value.

STRINGREADPROC
       formatPtr->stringReadProc provides the address of a proce-
       dure  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 com-
       mand 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

Tk			       4.0				3

Tk_CreatePhotoImageForTktLibrary ProcTk_CreatePhotoImageFormat(3)

       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  pro-
       cedure.	 The return value is a standard Tcl return value.

FILEWRITEPROC
       formatPtr->fileWriteProc provides the address of a  proce-
       dure  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 com-
       mand 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  struc-
       ture  pointed  to  by  blockPtr; see the manual page Find-
       Photo(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  char-
       acters  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  pro-
       cedure 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 com-
       mand 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

Tk			       4.0				4

Tk_CreatePhotoImageForTktLibrary ProcTk_CreatePhotoImageFormat(3)

       -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  for-
       matPtr->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

Tk			       4.0				5

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