Blog

You all know what a blog is by now :-) this is mine

Adding robots.txt to your Grails app

I just wanted to add a robots.txt file to Groupie, easy enough you say, as a matter of fact yes it is :-)

What I did was to add the following line to UrlMappings.groovy in the Configuration folder:-

"/robots.txt" (view: "/robots")

then created a robots.gsp file in the Views and Layouts folder that looks something like this:

<%@ page contentType="text/plain;charset=UTF-8" %>User-agent: *
Disallow: /blah/
Note no new-line before User-agent: * here is to remove the blank line left by the <%@ page...%> in the file.

Now when you go to http://nerderg.com/robots.txt you get a robots.txt, simple.

Solar Power

solar_north_side.jpg

Back in our old house in Canberra we decided to install Solar power as well as solar hot water. It suited the house since it was solar passive to a good degree and faced pretty much North.

We started out consuming something like 12kWh per day, but were able to average around 6kWh per day after checking what was using power and reducing the amount we used.

Below is a graph of the measurements I took while we were living there (just after we reduced out usage. You can see the output of the solar panels drop in winter. The really big red peaks in usage are when we needed to turn on the electric hot water booster for the solar hot water.

solarPanelOutput-vs-usage.png

Colour Picker Canvas

circle.pngI really quite liked the Color Sphere by Color Jack. However the code was a little, um, terse. Having a look at his code it looks like he uses the image as a reference and then computes the HSV values using the algorithm  that's used to produce the picture - pretty cool.

But wouldn't it be simpler to just pick the pixel in the image when you click?? Sure! but... you can't, due to javascript limitations/security. Damn. Oh wait what about <canvas>.

So I did a little experiment and here is the result (sorry won't work in IE8).

Canvas drawImage example 1

Oh, sorry I don't get Canvas yet
color is #346500

So here is the script:
// use jQuery on page load to draw the canvas image

$(function() {
      var ctx = document.getElementById('canvas').getContext('2d');
      var img = new Image();
      img.src = 'media/show/280';
      img.onload = function(){
        ctx.drawImage(img,0,0);
      }
      $('canvas').bind('mousemove', function(event){
        var x = event.pageX - event.currentTarget.offsetLeft
        var y = event.pageY - event.currentTarget.offsetTop;
        var ctx = document.getElementById('canvas').getContext('2d');
        var imgd = ctx.getImageData(x, y, 1, 1);
        var data = imgd.data;
        var out = $('#result');
        var hexString = RGBtoHex(data[0],data[1],data[2]);
        out.html("color is #" + hexString);
        out.attr("style","background-color: #" + hexString + ";");
      });
    }
);

//from http://www.linuxtopia.org/online_books/javascript_guides/javascript_faq/rgbtohex.htm

function RGBtoHex(R,G,B) {return toHex(R)+toHex(G)+toHex(B)}

function toHex(N) {
      if (N==null) return "00";
      N=parseInt(N); if (N==0 || isNaN(N)) return "00";
      N=Math.max(0,N); N=Math.min(N,255); N=Math.round(N);
      return "0123456789ABCDEF".charAt((N-N%16)/16)
           + "0123456789ABCDEF".charAt(N%16);
}


and the HTML looks like this:
<h2>Canvas <code>drawImage</code> example 1</h2>
<div>
<canvas id="canvas" width="370" height="370" >Oh, sorry I don't get Canvas yet</canvas>
</div>
<span style="" id="result"></span>

So enjoy :-)

Copyright © Peter McNeil 2010 ABN 919 5081 7346