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img-png(n)                            Img                           img-png(n)

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NAME
       img-png - Img, Portable Network Graphics format (png)

SYNOPSIS
       package require Tk

       package require img::png  ?1.4?

       image create photo ?name? ?options?

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DESCRIPTION
       The package img::png is a sub-package of Img. It can be loaded as a
       part of the complete Img support, via package require Img, or on its
       own, via package require img::png.

       Like all packages of Img it does not provide new commands, but extends
       the existing Tk command image so that it supports files containing
       raster images in the Portable Network Graphics format (png). More
       specifically img::png extends Tk's photo image type.

       The name of the new format handler is png.  This handler provides new
       additional configuration options. See section PNG OPTIONS for more
       detailed explanations.

       All of the above means that in a call like

       image create photo ?name? ?options?

       [1]    Image data in png format (options -data and -file) is detected
              automatically.

       [2]    The format name png is recognized by the option -format.  In
              addition the value for the option is treated as list and may
              contain any of the special options listed in section PNG
              OPTIONS.

PNG OPTIONS
       The handler provides the following options:

       -matte bool
              This option is supported for reading only.

              If set to false, a matte (alpha) channel is ignored during
              reading or writing. Default is true.

       -alpha float
              This option is supported for reading only.

              An additional alpha filtering for the overall image, which
              allows the background on which the image is displayed to show
              through.  This usually also has the effect of desaturating the
              image.  The alphaValue must be between 0.0 and 1.0.  Specifying
              an alpha value, overrides the setting of the matte flag, i.e.
              reading a file which has no alpha channel (Greyscale, RGB) will
              add an alpha channel to the image independent of the matte flag
              setting.

       The handler provides no true write options at all, but accepts pairs of
       keys and values when writing a PNG file. Each pair will be written as a
       named text chunk where the key provides the name of the chunk and the
       value its contents.  For example

                  png Author <name> Title <title> Description ...

TRANSPARENCY
       If you want to write images to disk which contain transparency
       information (e.g. PNG with alpha channel) you need at least Tk 8.3.

SEE ALSO
       img-bmp, img-dted, img-gif, img-ico, img-intro, img-jpeg, img-pcx, img-
       pixmap, img-png, img-ppm, img-ps, img-raw, img-sgi, img-sun, img-tga,
       img-tiff, img-window, img-xbm, img-xpm

KEYWORDS
       image handling, png, tk

COPYRIGHT
       Copyright (c) 1995-2009 Jan Nijtmans <nijtmans@users.sourceforge.net>

img-png                               1.4                           img-png(n)