From ab8a0a3e6e1af9c8e6e425e9db80041b668fb7a5 Mon Sep 17 00:00:00 2001
From: Samuel Clay <samuel@ofbrooklyn.com>
Date: Thu, 5 May 2011 17:55:57 -0400
Subject: [PATCH] New color luminosity algorithm. Used to detect whether a
 light or dark text color should be used in the River of News feed title
 floater bar.

---
 media/js/jquery.newsblur.js | 27 +++++++++++++++++++++++++++
 media/js/newsblur/reader.js | 12 +++++-------
 2 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/media/js/jquery.newsblur.js b/media/js/jquery.newsblur.js
index 96295d84c..38cbde456 100644
--- a/media/js/jquery.newsblur.js
+++ b/media/js/jquery.newsblur.js
@@ -130,6 +130,33 @@ NEWSBLUR.log = function(msg) {
     
     $.extend({
       
+        // Color format: {r: 1, g: .5, b: 0}
+        textColor: function(background_color) {
+            var contrast = function (color1, color2) {
+                var lum1 = luminosity(color1);
+                var lum2 = luminosity(color2);
+                if(lum1 > lum2)
+                return (lum1 + 0.05) / (lum2 + 0.05);
+                return (lum2 + 0.05) / (lum1 + 0.05);
+            };
+            
+            var luminosity = function (color) {
+                var r = color.r, g = color.g, b = color.b;
+                var red = (r <= 0.03928) ? r/12.92 : Math.pow(((r + 0.055)/1.055), 2.4);
+                var green = (g <= 0.03928) ? g/12.92 : Math.pow(((g + 0.055)/1.055), 2.4);
+                var blue = (b <= 0.03928) ? b/12.92 : Math.pow(((b + 0.055)/1.055), 2.4);
+                
+                return 0.2126 * red + 0.7152 * green + 0.0722 * blue;
+            };
+            
+            if (contrast(background_color, {r: 1, g: 1, b: 1}) > 
+                contrast(background_color, {r: .5, g: .5, b: .5})) {
+                return 'white';
+            } else {
+                return 'black';
+            }
+        },
+        
         favicon: function(feed_favicon, empty_on_missing) {
           
             if (feed_favicon && feed_favicon.indexOf('data:image/png;base64,') != -1) return feed_favicon;
diff --git a/media/js/newsblur/reader.js b/media/js/newsblur/reader.js
index 1a8cade84..66c249d45 100644
--- a/media/js/newsblur/reader.js
+++ b/media/js/newsblur/reader.js
@@ -2552,13 +2552,11 @@
             var color = feed.favicon_color;
             if (!color) return false;
             
-            var r = parseInt(color.substr(0, 2), 16);
-            var g = parseInt(color.substr(2, 2), 16);
-            var b = parseInt(color.substr(4, 2), 16);
-            var avg = (r + g + b) / 3;
-            
-            // 200/256 = #C6C6C6
-            return avg > 200;
+            var r = parseInt(color.substr(0, 2), 16) / 255.0;
+            var g = parseInt(color.substr(2, 2), 16) / 255.0;
+            var b = parseInt(color.substr(4, 2), 16) / 255.0;
+            console.log(['is_feed_floater_gradient_light', r, g, b, $.textColor({r: r, g: g, b: b})]);
+            return $.textColor({r: r, g: g, b: b}) != 'white';
         },
         
         generate_gradient: function(feed, type) {