NAME¶
img-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 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>