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img-png(3tk) Img img-png(3tk) 





NAME


img-png - Portable Network Graphics format (png)






SYNOPSIS


package require img::png ?2.0?










DESCRIPTION


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 [https://www.tcl.tk/man/tcl9.0/TkCmd/photo.html] image
  type.


The name of the new format handler is png. This handler
    provides new additional configuration options. See section 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 of option -format is treated as a
    list and may contain any of the special options listed in section
    Options.


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.






NOTES



  
[1]

  
Chapter Image Metadata of the Img manual page describes the
      parameters of the resolution related options.








OPTIONS


The handler provides the following options:



  

  
This option is supported for reading and writing. Available since version
      1.4.6.
    
If set to true, additional information about the read
        or written image is printed to stdout. Default is false.

  

  

  
This option is supported for reading only. Available since version 1.4.2.
    
An additional alpha filtering value 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
        alpha value must be between 0.0 and 1.0. Specifying an alpha value,
        overrides the setting of the -withalpha flag, i.e. reading a file
        which has no alpha channel (Grayscale, RGB) will add an alpha channel to
        the image independent of the -withalpha flag setting.

  

  

  
This option is supported for reading only. Available since version 1.4.6.
    
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.

  

  

  
This option is supported for reading and writing. Available since version
      1.4.1.
    
If set to false, an alpha channel is ignored during
        reading or writing. Default is true.

    
Note: This option was named -matte in previous
        versions and is still recognized.

  

  

  
This option is supported for writing only. Available since version 2.0.
    
Set the resolution values of the written image file. If
        yres is not specified, it is set to the value of xres.

    
If option is not specified, the DPI and aspect
        values of the metadata dictionary are written. If no metadata values are
        available, no resolution values are written.

  

  

  
This option is supported for writing only. Available since version 2.0.
    
Set the horizontal resolution value of the written image
      file.

  

  

  
This option is supported for writing only. Available since version 2.0.
    
Set the vertical resolution value of the written image
      file.

  

  

  
This option is supported for writing only. Available since version 2.0.
    
Each key-value pair will be written as a named text chunk
        where the key provides the name of the chunk and the value its contents.
        Currently the maximum number of -tag specifications are 10.

  








SEE ALSO


img, img-bmp, img-dted, img-flir, img-gif, img-ico, 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






COPYRIGHT


Copyright (c) 1995-2024 Jan Nijtmans <nijtmans@users.sourceforge.net>
Copyright (c) 2002-2024 Andreas Kupries <andreas_kupries@users.sourceforge.net>
Copyright (c) 2003-2024 Paul Obermeier <obermeier@users.sourceforge.net>








  

    2.0
    img-png