soren/scancalc.html

## scancalc.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>ScanCalc</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <style type="text/css">
      table { border-collapse:collapse; }
      th { background-color: #ccc; }
      th,td { padding:3px; }
      table,th,td { border: 1px solid #999; }
    </style>
  </head>
  <body>

    <p>ScanCalc is a small JavaScript utility to convert between centimeters (cm),
       pixels and dots/inch (dpi).</p>

    <script type="text/javascript">
      function cm_pixels_to_dpi() {
          if (document.scancalc.cm1.value == 0) {
              alert("cm cannot be zero");
          } else {
              document.scancalc.dp1.value = 2.54 * document.scancalc.px1.value
                                            / document.scancalc.cm1.value;
          }
      }

      function pixels_dpi_to_cm() {
          if (document.scancalc.dp2.value == 0) {
              alert("dpi cannot be zero");
          } else {
              document.scancalc.cm2.value = 2.54 * document.scancalc.px2.value
                                            / document.scancalc.dp2.value;
          }
      }

      function dpi_cm_to_pixels() {
          document.scancalc.px3.value = document.scancalc.dp3.value *
                                        document.scancalc.cm3.value / 2.54;
      }
    </script>

    <div align="center">
      <table>
        <tr><th>Scan Calc</th></tr>
        <tr><td>
          <form name="scancalc">
            <table>
              <tr>
                <td><input name=cm1 type=text size=5>&nbsp;cm</td>
                <td><input name=px1 type=text size=5>&nbsp;pixels</td>
                <td><input type=button value=" * " onClick="cm_pixels_to_dpi()"></td>
                <td><input name=dp1 type=text size=5>&nbsp;dpi</td>
              </tr>
              <tr>
                <td><input name=px2 type=text size=5>&nbsp;pixels</td>
                <td><input name=dp2 type=text size=5>&nbsp;dpi</td>
                <td><input type=button value=" * " onClick="pixels_dpi_to_cm()"></td>
                <td><input name=cm2 type=text size=5>&nbsp;cm</td>
              </tr>
              <tr>
                <td><input name=dp3 type=text size=5>&nbsp;dpi</td>
                <td><input name=cm3 type=text size=5>&nbsp;cm</td>
                <td><input type=button value=" * " onClick="dpi_cm_to_pixels()"></td>
                <td><input name=px3 type=text size=5>&nbsp;pixels</td>
              </tr>
            </table>
          </form>
        </td></tr>
      </table>
    </div>

    <p>The JavaScript and HTML code that is ScanCalc is public domain, use it
       as you wish. Either save this page, use <em>view source</em>. Even better
       <a href="https://gist.github.com/3058490" target="_blank">download it
       from github</a>.</p>

  </body>
</html>
	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
	"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<title>ScanCalc</title>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
	<style type="text/css">
	table { border-collapse:collapse; }
	th { background-color: #ccc; }
	th,td { padding:3px; }
	table,th,td { border: 1px solid #999; }
	</style>
	</head>
	<body>

	<p>ScanCalc is a small JavaScript utility to convert between centimeters (cm),
	pixels and dots/inch (dpi).</p>

	<script type="text/javascript">
	function cm_pixels_to_dpi() {
	if (document.scancalc.cm1.value == 0) {
	alert("cm cannot be zero");
	} else {
	document.scancalc.dp1.value = 2.54 * document.scancalc.px1.value
	/ document.scancalc.cm1.value;
	}
	}

	function pixels_dpi_to_cm() {
	if (document.scancalc.dp2.value == 0) {
	alert("dpi cannot be zero");
	} else {
	document.scancalc.cm2.value = 2.54 * document.scancalc.px2.value
	/ document.scancalc.dp2.value;
	}
	}

	function dpi_cm_to_pixels() {
	document.scancalc.px3.value = document.scancalc.dp3.value *
	document.scancalc.cm3.value / 2.54;
	}
	</script>

	<div align="center">
	<table>
	<tr><th>Scan Calc</th></tr>
	<tr><td>
	<form name="scancalc">
	<table>
	<tr>
	<td><input name=cm1 type=text size=5> cm</td>
	<td><input name=px1 type=text size=5> pixels</td>
	<td><input type=button value=" * " onClick="cm_pixels_to_dpi()"></td>
	<td><input name=dp1 type=text size=5> dpi</td>
	</tr>
	<tr>
	<td><input name=px2 type=text size=5> pixels</td>
	<td><input name=dp2 type=text size=5> dpi</td>
	<td><input type=button value=" * " onClick="pixels_dpi_to_cm()"></td>
	<td><input name=cm2 type=text size=5> cm</td>
	</tr>
	<tr>
	<td><input name=dp3 type=text size=5> dpi</td>
	<td><input name=cm3 type=text size=5> cm</td>
	<td><input type=button value=" * " onClick="dpi_cm_to_pixels()"></td>
	<td><input name=px3 type=text size=5> pixels</td>
	</tr>
	</table>
	</form>
	</td></tr>
	</table>
	</div>

	<p>The JavaScript and HTML code that is ScanCalc is public domain, use it
	as you wish. Either save this page, use <em>view source</em>. Even better
	<a href="https://gist.github.com/3058490" target="_blank">download it
	from github</a>.</p>

	</body>
	</html>