Ubuntu Manpage: img-jpeg - Joint Picture Expert Group format (jpeg)

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NAME

       img-jpeg - Joint Picture Expert Group format (jpeg)

SYNOPSIS

       package require img::jpeg ?2.0?

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DESCRIPTION

       package require img::jpeg

       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 Joint Picture Expert  Group  format  (jpeg).  More
       specifically img::jpeg extends Tk's photo [https://www.tcl.tk/man/tcl9.0/TkCmd/photo.html] image type.

       The  name of the new format handler is jpeg.  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 jpeg format (options -data and -file) is detected automatically.

       [2]    The format name jpeg 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::jpeg  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::jpeg.

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:

-verbose bool
This option is supported for reading and writing. Available since version 2.0.

If set to true, additional information about the read or written image is printed to stdout.
Default is false.

-fast This option is supported for reading only. Available since version 1.2.4.

If specified, it activates a processing mode which is fast, but provides only low-quality
information.

-grayscale
This option is supported for reading and writing. Available since version 1.2.4.

Usage of this option forces incoming images to grayscale and written images will be monochrome.

-optimize
This option is supported for writing only. Available since version 1.2.4.

If specified, it causes the writer to optimize the Huffman table used to encode the JPEG
coefficients.

-progressive
This option is supported for writing only. Available since version 1.2.4.

If specified, it causes the creation of a progressive JPEG file.

-quality n
This option is supported for writing only. Available since version 1.2.4.

It specifies the compression level as a quality percentage. The higher the quality, the less the
compression. The nominal range for n is 0...100. Useful values are in the range 5...95. The
default value is 75.

-smooth n
This option is supported for writing only. Available since version 1.2.4.

When used the writer will smooth the image before performing the compression. Values in the
10...30 are usually enough. The default is 0, i.e no smoothing.

-resolution xres ?yres?
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.

-xresolution xres
This option is supported for writing only. Available since version 2.0.

Set the horizontal resolution value of the written image file.

-yresolution yres
This option is supported for writing only. Available since version 2.0.

Set the vertical resolution value of the written image file.

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