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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>Calibration Format File (.cal)</title>
    <meta http-equiv="content-type" content="text/html;
      charset=ISO-8859-1">
    <meta name="author" content="Graeme Gill">
  </head>
  <body>
    <h2>Description of the .cal format</h2>
    Device calibration information. This is ASCII text, <a
      href="File_Formats.html#CGATS">CGATS</a>, Argyll specific format,
    used
    to hold a description of device setup information that brings it to
    a
    desired calibration state. Calibration files are created by <a
      href="synthcal.html">synthcal</a>, <a href="dispcal.html">dispcal</a>
    and <a href="printcal.html">printcal</a>.<br>
    <br>
    While fully compatible with the CGATS.5 Data Exchange Format, the
    particular required keywords and fields are unique to Argyll, hence
    an
    Argyll specific file identifier <span style="font-weight: bold;">CAL</span>
    is used to avoid confusion with standard ANSI or CGATS files.<br>
    <br>
    The <span style="font-weight: bold;">.cal</span> format changes
    from
    time to time with new releases, to add new functionality, but
    generally
    retains backwards compatibility. Note that in the description below,
    the word "may" indicates an optional component, while the word
    "shall"
    indicates a necessary component.<br>
    <br>
    Generally a .cal file contains only one table, the table containing
    the
    setup information. <br>
    <br>
    <br>
    The table contains the following:<br>
    <br>
    The file identifier (First 7 characters) shall be <span
      style="font-weight: bold;">CAL</span>.<br>
    <br>
    A <span style="font-weight: bold;">#</span> character introduces a
    comment.<br>
    <br>
    <span style="font-weight: bold;"><span style="font-weight: bold;"><span
          style="font-weight: bold;"></span></span></span>There may be <span
      style="font-weight: bold;">DESCRIPTOR</span>, <span
      style="font-weight: bold;">ORIGINATOR</span>, or <span
      style="font-weight: bold;">CREATED</span> keywords and values (as
    per
    CGATS).<br>
    <br>
    There shall be a <span style="font-weight: bold;">DEVICE_CLASS</span>
    keyword that has a value of <span style="font-weight: bold;">"OUTPUT</span>",
    "<span style="font-weight: bold;">DISPLAY</span>" or <span
      style="font-weight: bold;">"INPUT"</span>.<br>
    This indicates what type of device the calibration information is
    suitable for.<br>
    <br>
    A <span style="font-weight: bold;">"DISPLAY"</span> type device may
    have a <span style="font-weight: bold;">VIDEO_LUT_CALIBRATION_POSSIBLE
    </span>keyword that
    must have a value of "<span style="font-weight: bold;">NO</span>" or
    "<span style="font-weight: bold;">YES</span>", to indicate whether
    the display has the ability to be calibrated by loading VideoLUT
    values.<br>
    <br>
    There shall be a keyword <span style="font-weight: bold;">COLOR_REP</span>
    that has a value that indicates what colorspaces of the device
    values.
    The colorspaces shall be encoded with one&nbsp; or two letters
    per
    component. The device spaces shall use the
    following letter encoding:<br>
    <br>
    <span style="font-weight: bold;"><span style="font-weight: bold;"></span></span>&nbsp;&nbsp;&nbsp;
Cyan
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    C<br>
    &nbsp;&nbsp;&nbsp; Magenta &nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;
    &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp; M<br>
    &nbsp;&nbsp;&nbsp; Yellow &nbsp; &nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    Y<br>
    &nbsp;&nbsp;&nbsp; Black &nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    K<br>
    &nbsp;&nbsp;&nbsp; Orange &nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    O<br>
    &nbsp;&nbsp;&nbsp; Red
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    R<br>
    &nbsp;&nbsp;&nbsp; Green &nbsp; &nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    G<br>
    &nbsp;&nbsp;&nbsp; Blue &nbsp;&nbsp; &nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    B<br>
    &nbsp;&nbsp;&nbsp; White &nbsp;
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;
    &nbsp; &nbsp; &nbsp; &nbsp;&nbsp; W<br>
    &nbsp;&nbsp;&nbsp; Light Cyan
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    c<br>
    &nbsp;&nbsp;&nbsp; Light
Magenta&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    m<br>
    &nbsp;&nbsp;&nbsp; Light
Yellow&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    y<br>
    &nbsp;&nbsp;&nbsp; Light
Black&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    k<br>
    &nbsp;&nbsp;&nbsp; Medium Cyan&nbsp;
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2c<br>
    &nbsp;&nbsp;&nbsp; Medium Magenta
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    2m<br>
    &nbsp;&nbsp;&nbsp; Medium Yellow
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2y<br>
    &nbsp;&nbsp;&nbsp; Medium Black
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2k<br>
    &nbsp;&nbsp;&nbsp; Light Light Black &nbsp; &nbsp; &nbsp;&nbsp; 1k<br>
    <br>
    There may be an a prefix <span style="font-weight: bold;">i</span>
    preceding the device space letter encoding, indicating that although
    the space appears to be an additive space, it is in fact a
    subtractive
    device.<br>
    <br>
    Typical values might be: "<span style="font-weight: bold;">RGB</span><span
      style="font-weight: bold;"></span>" for an RGB display, "<span
      style="font-weight: bold;">iRGB</span><span style="font-weight:
      bold;"></span>"
    for an RGB printer, "<span style="font-weight: bold;">CMYK</span>"
    for
    a
    printer, "<span style="font-weight: bold;">RGB"</span> for an RGB
    scanner.<br>
    <br>
    The <span style="font-weight: bold;">NUMBER_OF_FIELDS</span>
    keyword
    shall have a value that indicates the number of fields in each data
    set, e.g. <span style="font-weight: bold;">4</span> (as per CGATS).<br>
    <br>
    The start of the declaration of the fields shall be marked by the <span
      style="font-weight: bold;">BEGIN_DATA_FORMAT</span> keyword (as
    per
    CGATS).<br>
    <br>
    The fields shall use the standard CGATS pattern of the full
    colorspace
    identified followed by the individual colorant identifier. There
    shall
    be an initial input index value identified by the letter <span
      style="font-weight: bold;">I</span>.<br>
    <br>
    For an RGB device, the
    following fields would be used:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <span style="font-weight: bold;">RGB_I</span>&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;
    The device value input value between 0.0 and 1.0.<br>
    &nbsp;&nbsp;&nbsp; <span style="font-weight: bold;">RGB_R</span>&nbsp;&nbsp;&nbsp;
&nbsp;
    The Red device value input value between 0.0 and 1.0.<br>
    &nbsp;&nbsp;&nbsp; <span style="font-weight: bold;">RGB_G</span>
    &nbsp;&nbsp; &nbsp; The Green device value input value between 0.0
    and
    1.0.<br>
    &nbsp;&nbsp;&nbsp; <span style="font-weight: bold;">RGB_B</span>
    &nbsp;&nbsp; &nbsp; The Blue device value input value between 0.0
    and
    1.0.<br>
    <br>
    The corresponding field names for a CMYK device would be <span
      style="font-weight: bold;">CMYK_I</span>, <span
      style="font-weight: bold;">CMYK_C</span>, <span
      style="font-weight: bold;">CMYK_M</span>, <span
      style="font-weight: bold;">CMYK_Y</span> and <span
      style="font-weight: bold;">CMYK_K</span>, etc.<br>
    <br>
    The definition of the fields shall be terminated by the <span
      style="font-weight: bold;">END_DATA_FORMAT</span> keyword (as per
    CGATS).<br>
    <br>
    The <span style="font-weight: bold;">NUMBER_OF_SETS</span> keyword
    shall have a value that indicates the number of sets of data, e.g. <span
      style="font-weight: bold;">256</span> (as per CGATS).<br>
    <br>
    The start of the values of the data sets shall be marked by the <span
      style="font-weight: bold;">BEGIN_DATA</span> keyword (as per
    CGATS).<br>
    <br>
    Each set of data shall be on one line, and shall be separated by
    white
    space. All values shall be normalized to lie between 0.0 and 1.0.<br>
    <br>
    The end of the values of the data sets shall be marked by the <span
      style="font-weight: bold;">END_DATA</span> keyword (as per CGATS).<br>
    <br>
    There may then be device type specific extra tables that hold target
    or
    device behavior information. These will be specific to the tool that
    creates that particular type of calibration.<br>
    <br>
    Generally any other keywords and values will be ignored.<br>
    <br>
    <br>
  </body>
</html>