img-png(n) Img img-png(n)______________________________________________________________________________NAMEimg-png - Img, Portable Network Graphics format (png)
SYNOPSIS
package require Tk
package require img::png ?1.4?
image create photo ?name? ?options?
______________________________________________________________________________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 read‐
ing 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 informa‐
tion (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)
