photo man page on Tru64

Man page or keyword search:  
man Server   12896 pages
apropos Keyword Search (all sections)
Output format
Tru64 logo
[printable version]

photo(n)		     Tk Built-In Commands		      photo(n)

______________________________________________________________________________

NAME
       photo - Full-color images

SYNOPSIS
       image create photo ?name? ?options?
_________________________________________________________________

DESCRIPTION
       A  photo is an image whose pixels can display any color or be transpar‐
       ent.  A photo image is stored internally in full	 color	(24  bits  per
       pixel),	and is displayed using dithering if necessary.	Image data for
       a photo image can be obtained from a file or a string,  or  it  can  be
       supplied	 from C code through a procedural interface.  At present, only
       GIF and PPM/PGM formats are supported, but an interface exists to allow
       additional  image  file	formats	 to be added easily.  A photo image is
       transparent in regions where no image data has been supplied.

CREATING PHOTOS
       Like all images, photos are created using  the  image  create  command.
       Photos support the following options:

       -data string
	      Specifies	 the contents of the image as a string.	 The format of
	      the string must be one of those for which there is an image file
	      format  handler that will accept string data.  If both the -data
	      and -file options are specified, the -file option	 takes	prece‐
	      dence.

       -format format-name
	      Specifies	 the  name  of	the file format for the data specified
	      with the -data or -file option.

       -file name
	      name gives the name of a file that is to be read to supply  data
	      for  the	photo image.  The file format must be one of those for
	      which there is an image file format handler that can read data.

       -gamma value
	      Specifies that the colors allocated for displaying this image in
	      a	 window	 should be corrected for a non-linear display with the
	      specified gamma exponent value.  (The intensity produced by most
	      CRT  displays  is a power function of the input value, to a good
	      approximation; gamma is the exponent and is typically around 2).
	      The  value  specified  must  be  greater than zero.  The default
	      value is one (no correction).  In general, values	 greater  than
	      one  will	 make the image lighter, and values less than one will
	      make it darker.

       -height number
	      Specifies the height of the image, in pixels.   This  option  is
	      useful primarily in situations where the user wishes to build up
	      the contents of the image piece by piece.	 A value of zero  (the
	      default)	allows the image to expand or shrink vertically to fit
	      the data stored in it.

       -palette palette-spec
	      Specifies the resolution of the color cube to be	allocated  for
	      displaying  this	image, and thus the number of colors used from
	      the colormaps of the windows where it is	displayed.   The  pal‐
	      ette-spec string may be either a single decimal number, specify‐
	      ing the number of shades of gray to use, or three	 decimal  num‐
	      bers  separated  by slashes (/), specifying the number of shades
	      of red, green and blue to use, respectively.  If the first  form
	      (a  single number) is used, the image will be displayed in mono‐
	      chrome (i.e., grayscale).

       -width number
	      Specifies the width of the image, in pixels.    This  option  is
	      useful primarily in situations where the user wishes to build up
	      the contents of the image piece by piece.	 A value of zero  (the
	      default)	allows	the  image to expand or shrink horizontally to
	      fit the data stored in it.

IMAGE COMMAND
       When a photo image is created, Tk also creates a new command whose name
       is  the	same as the image.  This command may be used to invoke various
       operations on the image.	 It has the following general form:
	      imageName option ?arg arg ...?
       Option and the args determine the exact behavior of the command.

       Those options that write data to the image generally expand the size of
       the  image, if necessary, to accommodate the data written to the image,
       unless the user has specified non-zero values  for  the	-width	and/or
       -height	configuration  options, in which case the width and/or height,
       respectively, of the image will not be changed.

       The following commands are possible for photo images:

       imageName blank
	      Blank the image; that is, set the entire image to have no	 data,
	      so  it  will  be displayed as transparent, and the background of
	      whatever window it is displayed in will show through.

       imageName cget option
	      Returns the current value of the configuration option  given  by
	      option.  Option may have any of the values accepted by the image
	      create photo command.

       imageName configure ?option? ?value option value ...?
	      Query or modify the configuration options for the image.	If  no
	      option is specified, returns a list describing all of the avail‐
	      able options for imageName (see Tk_ConfigureInfo for information
	      on  the  format  of  this list).	If option is specified with no
	      value, then the command returns a list describing the one	 named
	      option (this list will be identical to the corresponding sublist
	      of the value returned if no option is  specified).   If  one  or
	      more option-value pairs are specified, then the command modifies
	      the given option(s) to have the given value(s);	in  this  case
	      the command returns an empty string.  Option may have any of the
	      values accepted by the image create photo command.

       imageName copy sourceImage ?option value(s) ...?
	      Copies a region from the image called sourceImage (which must be
	      a	 photo	image)	to  the	 image called imageName, possibly with
	      pixel zooming and/or subsampling.	 If no options are  specified,
	      this  command  copies  the  whole of sourceImage into imageName,
	      starting at  coordinates	(0,0)  in  imageName.	The  following
	      options may be specified:

	      -from x1 y1 x2 y2
		     Specifies a rectangular sub-region of the source image to
		     be copied.	 (x1,y1) and (x2,y2) specify diagonally	 oppo‐
		     site  corners  of	the  rectangle.	  If x2 and y2 are not
		     specified, the default value is the  bottom-right	corner
		     of	 the source image.  The pixels copied will include the
		     left and top edges of the specified rectangle but not the
		     bottom or right edges.  If the -from option is not given,
		     the default is the whole source image.

	      -to x1 y1 x2 y2
		     Specifies a rectangular  sub-region  of  the  destination
		     image to be affected.  (x1,y1) and (x2,y2) specify diago‐
		     nally opposite corners of the rectangle.  If  x2  and  y2
		     are  not specified, the default value is (x1,y1) plus the
		     size of the source region (after subsampling and zooming,
		     if	 specified).   If  x2 and y2 are specified, the source
		     region will be replicated if necessary to fill the desti‐
		     nation region in a tiled fashion.

	      -shrink
		     Specifies	that  the size of the destination image should
		     be reduced, if necessary, so that the region being copied
		     into  is  at  the bottom-right corner of the image.  This
		     option will not affect the width or height of  the	 image
		     if the user has specified a non-zero value for the -width
		     or -height configuration option, respectively.

	      -zoom x y
		     Specifies that the source region should be magnified by a
		     factor  of x in the X direction and y in the Y direction.
		     If y is not given, the default value is the  same	as  x.
		     With  this option, each pixel in the source image will be
		     expanded into a block of x x y pixels in the  destination
		     image,  all the same color.  x and y must be greater than
		     0.

	      -subsample x y
		     Specifies that the source image should be reduced in size
		     by	 using only every xth pixel in the X direction and yth
		     pixel in the Y direction.	Negative values will cause the
		     image  to be flipped about the Y or X axes, respectively.
		     If y is not given, the default value is the same as x.

       imageName get x y
	      Returns the color of the pixel at coordinates (x,y) in the image
	      as  a list of three integers between 0 and 255, representing the
	      red, green and blue components respectively.

       imageName put data ?-to x1 y1 x2 y2?
	      Sets pixels in imageName to the colors specified in data.	  data
	      is  used to form a two-dimensional array of pixels that are then
	      copied into the imageName.  data is structured as a list of hor‐
	      izontal  rows,  from  top	 to bottom, each of which is a list of
	      colors, listed from left to right.  Each color may be  specified
	      by  name	(e.g.,	blue)  or in hexadecimal form (e.g., #2376af).
	      The -to option can be used to specify the area of	 imageName  to
	      be affected.  If only x1 and y1 are given, the area affected has
	      its top-left corner at (x1,y1) and is the same size as the array
	      given  in data.  If all four coordinates are given, they specify
	      diagonally opposite corners of the affected rectangle,  and  the
	      array given in data will be replicated as necessary in the X and
	      Y directions to fill the rectangle.

       imageName read filename ?option value(s) ...?
	      Reads image data from the file named filename  into  the	image.
	      This  command  first searches the list of image file format han‐
	      dlers for a handler that can interpret the data in filename, and
	      then reads the image in filename into imageName (the destination
	      image).  The following options may be specified:

	      -format format-name
		     Specifies the format  of  the  image  data	 in  filename.
		     Specifically, only image file format handlers whose names
		     begin with format-name will be used while	searching  for
		     an image data format handler to read the data.

	      -from x1 y1 x2 y2
		     Specifies a rectangular sub-region of the image file data
		     to be copied to the destination image.  If only x1 and y1
		     are  specified,  the  region  extends from (x1,y1) to the
		     bottom-right corner of the image in the image  file.   If
		     all  four	coordinates are specified, they specify diago‐
		     nally opposite corners or the region.   The  default,  if
		     this  option  is not specified, is the whole of the image
		     in the image file.

	      -shrink
		     If this option, the size of imageName will be reduced, if
		     necessary,	 so  that the region into which the image file
		     data are read is at the bottom-right corner of the image‐
		     Name.  This option will not affect the width or height of
		     the image if the user has specified a non-zero value  for
		     the -width or -height configuration option, respectively.

	      -to x y
		     Specifies	the  coordinates of the top-left corner of the
		     region of imageName into which data from filename are  to
		     be read.  The default is (0,0).

       imageName redither
	      The  dithering  algorithm used in displaying photo images propa‐
	      gates quantization errors from one pixel to its  neighbors.   If
	      the image data for imageName is supplied in pieces, the dithered
	      image may not be exactly correct.	 Normally  the	difference  is
	      not noticeable, but if it is a problem, this command can be used
	      to recalculate the dithered image in each window where the image
	      is displayed.

       imageName write filename ?option value(s) ...?
	      Writes  image data from imageName to a file named filename.  The
	      following options may be specified:

	      -format format-name
		     Specifies the name of the image file format handler to be
		     used  to  write the data to the file.  Specifically, this
		     subcommand searches for  the  first  handler  whose  name
		     matches  a initial substring of format-name and which has
		     the capability to write an image file.  If this option is
		     not  given,  this	subcommand uses the first handler that
		     has the capability to write an image file.

	      -from x1 y1 x2 y2
		     Specifies a rectangular region of imageName to be written
		     to	 the image file.  If only x1 and y1 are specified, the
		     region extends from (x1,y1) to the bottom-right corner of
		     imageName.	 If all four coordinates are given, they spec‐
		     ify  diagonally  opposite	corners	 of  the   rectangular
		     region.  The default, if this option is not given, is the
		     whole image.

IMAGE FORMATS
       The photo image code is structured to  allow  handlers  for  additional
       image  file formats to be added easily.	The photo image code maintains
       a list of these handlers.  Handlers are added to the list by  register‐
       ing  them  with	a  call to Tk_CreatePhotoImageFormat.  The standard Tk
       distribution comes with handlers for PPM/PGM and GIF formats, which are
       automatically registered on initialization.

       When reading an image file or processing string data specified with the
       -data configuration option, the photo image code invokes	 each  handler
       in  turn	 until one is found that claims to be able to read the data in
       the file or string.  Usually this will find the correct handler, but if
       it  doesn't, the user may give a format name with the -format option to
       specify which handler to use.  In fact the photo image  code  will  try
       those  handlers	whose  names  begin  with the string specified for the
       -format option (the comparison is case-insensitive).  For  example,  if
       the user specifies -format gif, then a handler named GIF87 or GIF89 may
       be invoked, but a handler named JPEG may not (assuming that  such  han‐
       dlers had been registered).

       When writing image data to a file, the processing of the -format option
       is slightly different: the string value given for  the  -format	option
       must  begin  with  the  complete name of the requested handler, and may
       contain additional information following that, which  the  handler  can
       use,  for  example, to specify which variant to use of the formats sup‐
       ported by the handler.

COLOR ALLOCATION
       When a photo image is displayed in a window, the photo image code allo‐
       cates colors to use to display the image and dithers the image, if nec‐
       essary, to display a reasonable approximation to the  image  using  the
       colors  that  are available.  The colors are allocated as a color cube,
       that is, the number of colors allocated is the product of the number of
       shades of red, green and blue.

       Normally,  the  number of colors allocated is chosen based on the depth
       of the window.  For example, in an 8-bit PseudoColor window, the	 photo
       image  code  will attempt to allocate seven shades of red, seven shades
       of green and four shades of blue, for a total  of  198  colors.	 In  a
       1-bit  StaticGray  (monochrome)	window,	 it  will allocate two colors,
       black and white.	 In a 24-bit DirectColor or TrueColor window, it  will
       allocate	 256 shades each of red, green and blue.  Fortunately, because
       of the way that pixel values can be combined in DirectColor  and	 True‐
       Color  windows,	this only requires 256 colors to be allocated.	If not
       all of the colors can be allocated, the photo image  code  reduces  the
       number of shades of each primary color and tries again.

       The  user  can  exercise	 some control over the number of colors that a
       photo image uses with  the  -palette  configuration  option.   If  this
       option  is used, it specifies the maximum number of shades of each pri‐
       mary color to try to allocate.  It can also be used to force the	 image
       to be displayed in shades of gray, even on a color display, by giving a
       single number rather than three numbers separated by slashes.

CREDITS
       The photo image type was designed and implemented  by  Paul  Mackerras,
       based  on  his  earlier	photo  widget  and  some suggestions from John
       Ousterhout.

KEYWORDS
       photo, image, color

Tk				      4.0			      photo(n)
[top]
                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 
More information is available in HTML format for server Tru64

List of man pages available for Tru64

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net