'\"
'\" Generated from file 'format-header\&.inc' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 1995-2023 Jan Nijtmans <nijtmans@users\&.sourceforge\&.net>
'\"
.TH "img-png" 3tk 1\&.4 img-png "Img"
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.SH NAME
img-png \- Img, Portable Network Graphics format (png)
.SH SYNOPSIS
package require \fBTk \fR
.sp
package require \fBimg::png  ?1\&.4?\fR
.sp
\fBimage\fR \fBcreate photo\fR ?\fIname\fR? ?\fIoptions\fR?
.sp
.BE
.SH DESCRIPTION
\fBpackage require img::png\fR\&.
.PP
Like all packages of \fBImg\fR it does \fInot\fR provide new
commands, but extends the existing \fBTk\fR command \fBimage\fR so
that it supports files containing raster images in the
Portable Network Graphics format (png)\&. More specifically
\fBimg::png\fR extends \fBTk\fR's \fBphoto\fR
image type\&.
.PP
The name of the new format handler is \fBpng\fR\&.
.PP
The package \fBimg::png\fR is a sub-package of
\fBImg\fR\&. It can be loaded as a part of the complete Img support,
via \fBpackage require Img\fR, or on its own, via
\fBpackage require img::png\fR\&.
.PP
This handler provides new additional configuration options\&. See
section \fBPNG OPTIONS\fR for more detailed explanations\&.
.PP
All of the above means that in a call like
.TP
\fBimage\fR \fBcreate photo\fR ?\fIname\fR? ?\fIoptions\fR?
.PP
.IP [1]
Image data in png format (options \fB-data\fR and \fB-file\fR) is
detected automatically\&.
.IP [2]
The format name \fBpng\fR is recognized by the option \fB-format\fR\&.
In addition the value for the option is treated as list and may
contain any of the special options listed in section
\fBPNG OPTIONS\fR\&.
.PP
.SH "PNG OPTIONS"
The handler provides the following options:
.TP
\fB-verbose\fR \fIbool\fR
This option is supported for reading only\&.
.sp
If set to \fBtrue\fR, additional information about the file format
is printed to stdout\&. Default is \fBfalse\fR\&.
.TP
\fB-gamma\fR \fIfloat\fR
This option is supported for reading only\&.
.sp
Use the specified gamma value when reading an image\&.
This option overwrites gamma values specified in the file\&.
If this option is not specified and no gamma value is in the file,
a default value of 1\&.0 is used\&.
.TP
\fB-matte\fR \fIbool\fR
This option is supported for reading only\&.
.sp
If set to \fBfalse\fR, a matte (alpha) channel is ignored
during reading or writing\&. Default is \fBtrue\fR\&.
.TP
\fB-alpha\fR \fIfloat\fR
This option is supported for reading only\&.
.sp
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\&.
.PP
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
.CS


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

.CE
.SH TRANSPARENCY
If you want to write images to disk which contain transparency
information (e\&.g\&. PNG with alpha channel) you need at least
\fBTk\fR 8\&.3\&.
.PP
.SH "SEE ALSO"
img-bmp, img-dted, img-flir, 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
.SH KEYWORDS
image handling, png, tk
.SH COPYRIGHT
.nf
Copyright (c) 1995-2023 Jan Nijtmans <nijtmans@users\&.sourceforge\&.net>

.fi