title: How do I get graphicsmagick to draw a line inside a BMP file?
body: <p>I've installed GraphicsMagick and the gm command responds inside the shell.
  I have a BMP file of 400 by 400 white pixels.
  I tried this</p>
  <pre><code>gm convert -draw 'line 10,10 200,200' blank_canvas.bmp
  </code></pre>
  <p>but all I got was</p>
  <pre><code>gm convert unable to open file (10,10)[No such file or directory]
  </code></pre>
  <p>I also tried</p>
  <pre><code>gm convert blank_canvas.bmp -draw 'line 10,10 200,200'
  </code></pre>
  <p>and got</p>
  <pre><code>gm convert: Non-conforming drawing primitive definition (line) [No such file or directory].
  </code></pre>
  <p>And while we are at it, how do I get it to draw a big number of lines, inputing the data from a text file?</p>