libvips/doc/reference/using-command-line.xml

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<refentry id="using-cli">
  <refmeta>
    <refentrytitle>VIPS from the command-line</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo>VIPS Library</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>Using VIPS</refname>
    <refpurpose>How to use the VIPS library from the command-line</refpurpose>
  </refnamediv>

  <refsect1 id="using-command-line">
    <title>Using VIPS from the command-line</title>
    <para>
      Use the <command>vips</command> command to execute VIPS operations from 
      the command-line. You can show all classes with:

      <literallayout>
        <userinput>vips list classes</userinput>
      </literallayout>

      This produces output something like:

      <literallayout>
        <userinput>VipsOperation (operation), operations</userinput>
        <userinput>  VipsSystem (system), run an external command</userinput>
        <userinput>    VipsArithmetic (arithmetic), arithmetic operations</userinput>
        <userinput>      VipsBinary (binary), binary operations</userinput>
        <userinput>        VipsAdd (add), add two images</userinput>
        <userinput>        .... and so on</userinput>
      </literallayout>

      Each line shows the canonical name of the class (for example 
      <literal>VipsAdd</literal>), the class nickname 
      (<literal>add</literal> in this case), and a short description. 
      Some subclasses of operation will show more, for example subclasses of 
      <literal>VipsForeign</literal> will show some of the extra flags 
      supported by the file load/save operations. 

      You can get help on a specific operation by running it with no arguments,
      for example:

      <literallayout>
        <userinput>vips gamma</userinput>
      </literallayout>

      produces the output:

      <literallayout>
        <userinput>gamma an image</userinput>
        <userinput>usage:</userinput>
        <userinput>   gamma in out</userinput>
        <userinput>where:</userinput>
        <userinput>   in           - Input image, input VipsImage</userinput>
        <userinput>   out          - Output image, output VipsImage</userinput>
        <userinput>optional arguments:</userinput>
        <userinput>   exponent     - Gamma factor, input gdouble</userinput>
        <userinput>                    default: 2.4 </userinput>
        <userinput>                    min: 1e-06, max: 1000 </userinput>
        <userinput>operation flags: sequential-unbuffered</userinput>
      </literallayout>

      <command>vips gamma</command> applies a gamma factor to an image. By 
      default, it uses 2.4, the sRGB gamma factor, but you can specify any 
      gamma with the <literal>exponent</literal> option. You can use the 
      C API docs for <function>vips_gamma()</function> if you need more 
      information. 

      Use it from the command-line like this:

      <literallayout>
        <userinput>vips gamma k2.jpg x.jpg --exponent 0.42</userinput>
      </literallayout>

      This will read file <literal>k2.jpg</literal>, un-gamma it, and 
      write the result to file <literal>x.jpg</literal>.

      Some operations take arrays of values as arguments, for example, 
      <command>vips affine</command> needs an array of four numbers for the 
      2x2 transform matrix. You pass arrays as space-separated lists, for 
      example:

      <literallayout>
        <userinput>vips affine k2.jpg x.jpg "2 0 0 1"</userinput>
      </literallayout>

      Or <command>vips bandjoin</command> needs an array of input images to 
      join, run it like this:

      <literallayout>
        <userinput>vips bandjoin "k2.jpg k4.jpg" x.tif</userinput>
      </literallayout>

      <command>vips</command> will automatically convert between image file 
      formats for you. Input images are detected by sniffing their first few 
      bytes; output formats are set from the filename suffix. You can see a 
      list of all the supported file formats with something like:

      <literallayout>
        <userinput>vips list classes | grep -i foreign</userinput>
      </literallayout>

      Then get a list of the options a format supports with, for example:

      <literallayout>
        <userinput>vips jpegsave</userinput>
      </literallayout>

      You can pass options to the implicit load and save operations enclosed 
      in square brackets after the filename. For example:

      <literallayout>
        <userinput>vips affine k2.jpg x.jpg[Q=90,strip] "2 0 0 1"</userinput>
      </literallayout>

      Will write <literal>x.jpg</literal> at quality level 90 and will 
      strip all metadata from the image.

      Finally, <command>vips</command> has a couple of useful extra options. 

      <itemizedlist>
        <listitem>
          <para>
            Use <option>--vips-progress</option> to get 
            <command>vips</command> to display a simple progress indicator. 
          </para>
        </listitem>

        <listitem>
          <para>
            Use <option>--vips-leak</option> and <command>vips</command> will 
            leak-test on exit, and also display an estimate of peak memory use.
          </para>
        </listitem>
      </itemizedlist>
    </para>

    <para>
      VIPS comes with a couple of other useful programs. 
      <command>vipsheader</command> is a command which can print image header
      fields. <command>vipsedit</command> can change fields in vips format 
      images. <command>vipsthumbnail</command> can make image thumbnails 
      quickly. 

    </para>
  </refsect1>

</refentry>