img-png(n)

1img-png(n)                            Img                           img-png(n)
2
3
4
5______________________________________________________________________________
6

NAME

8       img-png - Img, Portable Network Graphics format (png)
9

SYNOPSIS

11       package require Tk
12
13       package require img::png  ?1.4?
14
15       image create photo ?name? ?options?
16
17______________________________________________________________________________
18

DESCRIPTION

20       The  package  img::png  is  a sub-package of Img. It can be loaded as a
21       part of the complete Img support, via package require Img,  or  on  its
22       own, via package require img::png.
23
24       Like  all packages of Img it does not provide new commands, but extends
25       the existing Tk command image so  that  it  supports  files  containing
26       raster  images  in  the  Portable  Network  Graphics format (png). More
27       specifically img::png extends Tk's photo image type.
28
29       The name of the new format handler is png.  This handler  provides  new
30       additional  configuration options. See section PNG OPTIONS for more de‐
31       tailed explanations.
32
33       All of the above means that in a call like
34
35       image create photo ?name? ?options?
36
37       [1]    Image data in png format (options -data and -file)  is  detected
38              automatically.
39
40       [2]    The format name png is recognized by the option -format.  In ad‐
41              dition the value for the option is treated as list and may  con‐
42              tain any of the special options listed in section PNG OPTIONS.
43

PNG OPTIONS

45       The handler provides the following options:
46
47       -verbose bool
48              This option is supported for reading only.
49
50              If  set to true, additional information about the file format is
51              printed to stdout. Default is false.
52
53       -gamma float
54              This option is supported for reading only.
55
56              Use the specified gamma value when reading an image.   This  op‐
57              tion overwrites gamma values specified in the file.  If this op‐
58              tion is not specified and no gamma value is in the file,  a  de‐
59              fault value of 1.0 is used.
60
61       -matte bool
62              This option is supported for reading only.
63
64              If set to false, a matte (alpha) channel is ignored during read‐
65              ing or writing. Default is true.
66
67       -alpha float
68              This option is supported for reading only.
69
70              An additional alpha filtering for the overall image,  which  al‐
71              lows  the  background  on  which  the image is displayed to show
72              through.  This usually also has the effect of  desaturating  the
73              image.   The alphaValue must be between 0.0 and 1.0.  Specifying
74              an alpha value, overrides the setting of the  matte  flag,  i.e.
75              reading  a file which has no alpha channel (Greyscale, RGB) will
76              add an alpha channel to the image independent of the matte  flag
77              setting.
78
79       The handler provides no true write options at all, but accepts pairs of
80       keys and values when writing a PNG file. Each pair will be written as a
81       named  text  chunk where the key provides the name of the chunk and the
82       value its contents.  For example
83
84
85                  png Author <name> Title <title> Description ...
86
87

TRANSPARENCY

89       If you want to write images to disk which contain transparency informa‐
90       tion (e.g. PNG with alpha channel) you need at least Tk 8.3.
91

KEYWORDS

98       image handling, png, tk
99

COPYRIGHT

101       Copyright (c) 1995-2009 Jan Nijtmans <nijtmans@users.sourceforge.net>
102
103
104
105
106img-png                               1.4                           img-png(n)