Reader

reader.js

(function(){
function getColor(tag) {
   m = tag.match(/^rgb\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\)$/i);
   if ( m )
     return [parseInt(m[1]),parseInt(m[2]),parseInt(m[3]),255];
   m = tag.match(/^rgba\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*\)$/i);
   return m ? [parseInt(m[1]),parseInt(m[2]),parseInt(m[3]),parseInt(m[4])] : null;
}

function realBackgroundColor(elem) {
   if (!elem) return [0,0,0,0];
   var style = getComputedStyle(elem);
   if (style.backgroundImage !== 'none')
      return undefined;
   var color = getColor(style.backgroundColor);
   if (!color)
      return undefined;
   if (color[3])
      return color;
   else
      return realBackgroundColor(elem.parentElement);
}   

var nodes=document.body.getElementsByTagName('*');
var pageBack=getColor(getComputedStyle(document.body).backgroundColor);
   
if (pageBack[3] < 255) {
   for (var j=0;j<3;j++) {
      pageBack[j] = Math.floor((pageBack[j] * pageBack[3] + 255 * (255-pageBack[3])) / 255);
      pageBack[3] = 255;
    }
}
 
if (pageBack[0]+pageBack[1]+pageBack[2] < 150) {
   document.body.style.backgroundColor = "rgb(0,0,0)";
}

if (pageBack[0]+pageBack[1]+pageBack[2] > 255*3-150) {
   document.body.style.backgroundColor = "rgb(255,255,255)";
}

for (var i=0; i<nodes.length; i++) {
  if (nodes[i].style) {
    var style = getComputedStyle(nodes[i]);
    nodes[i].style.fontFamily="Georgia, Utopia, \"Palatino Linotype\", Palatino, serif";
    if (style.textAlign == "left" || style.textAlign == "start") {
      nodes[i].style.textAlign = "justify";
    }    
    var fore = getColor(style.color);
    var back = realBackgroundColor(nodes[i]);
    if (back === undefined) {
      back = [255,255,255,255];
    }
    if (! fore) {
      fore = [0,0,0,255];
    }
    if (fore[0] + fore[1] + fore[2] <= back[0] + back[1] + back[2]) {
      for (var j=0; j<3; j++) {
        if (fore[j] < 200)
          fore[j] = 0;
      } 
      if(nodes[i].href)
         nodes[i].style.color = "rgb(0,0,128)";
      else
         nodes[i].style.color = "rgb("+fore[0]+","+fore[1]+","+fore[2]+")";
    }
    else {
      if(nodes[i].href)
         nodes[i].style.color = "rgb(0,0,255)";
      else
         nodes[i].style.color = "rgb(255,255,255)";
    }
  }
}
})()