From 8c093f2c724fe9fd58d6c111212254354fe9e455 Mon Sep 17 00:00:00 2001
From: MoonFlyer <moonflyerho@users.noreply.github.com>
Date: Sat, 8 Aug 2015 17:49:17 +0800
Subject: [PATCH] add down scale function for thumb (better quality)

---
 image-resizer.js | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/image-resizer.js b/image-resizer.js
index d3ed31b..9d89439 100644
--- a/image-resizer.js
+++ b/image-resizer.js
@@ -32,6 +32,45 @@ IR.ImageResizer = (function() {
 
         return canvas.toDataURL();
     };
+    
+    var thumb = function(image, maxWidth, maxHeight) {
+
+        var cwidth = 0;
+        var cheight = 0;
+        // set the correct accepted dimensions on the canvas
+        if (image.width > image.height) {
+            if (image.width > maxWidth) {
+                cheight = image.height * maxWidth / image.width;	        // maintain aspect ratio
+                cwidth = maxWidth;
+            }
+        } else {
+            if (image.height > maxHeight) {
+                cwidth = image.width * maxHeight / image.height;
+                cheight = maxHeight;
+            }
+        }
+        
+        // Step it down several times
+        var can2 = document.createElement('canvas');
+        can2.width = cwidth*8;
+        can2.height = cheight*8;
+        var ctx2 = can2.getContext('2d');
+        
+        // Draw it at 1/2 size 3 times (step down three times)
+        
+        ctx2.drawImage(img, 0, 0, cwidth*4, cheight*4);
+        ctx2.drawImage(can2, 0, 0, cwidth*4, cheight*4, 0, 0, cwidth*2, cheight*2);
+        ctx2.drawImage(can2, 0, 0, cwidth*2, cheight*2, 0, 0, cwidth, cheight);
+        
+        
+        var can = document.getElementById('canvas1');
+        can.width = cwidth;
+        can.height = cheight;        
+        var ctx = can.getContext('2d');
+        ctx.drawImage(can2, 0, 0, cwidth, cheight, 0, 0, cwidth, cheight);        
+
+        return can.toDataURL();
+    };
 
     /*
      * Converts a data URI object to a Blob object
@@ -55,4 +94,4 @@ IR.ImageResizer = (function() {
         toBlob: toBlob
     };
 
-})();
\ No newline at end of file
+})();