1 files changed, 50 insertions, 0 deletions
diff --git a/src/library_browser.js b/src/library_browser.js
new file mode 100644
index 00000000..ccc13698
--- /dev/null
+++ b/src/library_browser.js
@@ -0,0 +1,50 @@
+// Utilities for browser environments
+
+mergeInto(Library, {
+  $Browser: {
+    syncLoad: function(url) {
+      var xhr = new XMLHttpRequest();
+      xhr.open("GET", url, false);
+      xhr.send(null);
+      var buffer = xhr.mozResponseArrayBuffer;
+      return new Uint8Array(buffer);
+    },
+
+    // Given binary data for an image, in a format like PNG or JPG, we convert it
+    // to flat pixel data. We do so using the browser's native code.
+    decodeImage: function(pixels, format) {
+      function encodeBase64(data) {
+        var BASE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
+        var PAD = '=';
+        var ret = '';
+        var leftchar = 0;
+        var leftbits = 0;
+        for (var i = 0; i < data.length; i++) {
+          leftchar = (leftchar << 8) | data[i];
+          leftbits += 8;
+          while (leftbits >= 6) {
+            var curr = (leftchar >> (leftbits-6)) & 0x3f;
+            leftbits -= 6;
+            ret += BASE[curr];
+          }
+        }
+        if (leftbits == 2) {
+          ret += BASE[(leftchar&3) << 4];
+          ret += PAD + PAD;
+        } else if (leftbits == 4) {
+          ret += BASE[(leftchar&0xf) << 2];
+          ret += PAD;
+        }
+        return ret;
+      }
+      var img = new Image();
+      var canvas = document.createElement('canvas');
+      img.src = 'data:image/' + format + ';base64,' + encodeBase64(pixels);
+      var ctx = canvas.getContext('2d');
+      ctx.drawImage(Module.img, 0, 0);
+      var imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
+      return imageData;
+    },
+  }
+});
+