diff --git a/src/api.js b/src/api.js
index 4e7ce4e76..6c862a91b 100644
--- a/src/api.js
+++ b/src/api.js
@@ -311,13 +311,19 @@ var PDFPageProxy = (function PDFPageProxyClosure() {
     ensureFonts: function PDFPageProxy_ensureFonts(fonts, callback) {
       this.stats.time('Font Loading');
       // Convert the font names to the corresponding font obj.
+      var fontObjs = [];
       for (var i = 0, ii = fonts.length; i < ii; i++) {
-        fonts[i] = this.objs.objs[fonts[i]].data;
+        var obj = this.objs.objs[fonts[i]].data;
+        if (obj.error) {
+          warn('Error during font loading: ' + obj.error);
+          continue;
+        }
+        fontObjs.push(obj);
       }
 
       // Load all the fonts
       FontLoader.bind(
-        fonts,
+        fontObjs,
         function pageEnsureFontsFontObjs(fontObjs) {
           this.stats.timeEnd('Font Loading');
 
@@ -565,7 +571,12 @@ var WorkerTransport = (function WorkerTransportClosure() {
 
             // At this point, only the font object is created but the font is
             // not yet attached to the DOM. This is done in `FontLoader.bind`.
-            var font = new Font(name, file, properties);
+            var font;
+            try {
+              font = new Font(name, file, properties);
+            } catch (e) {
+              font = new ErrorFont(e);
+            }
             this.objs.resolve(id, font);
             break;
           default:
diff --git a/src/fonts.js b/src/fonts.js
index 4aef0962a..4af42265d 100644
--- a/src/fonts.js
+++ b/src/fonts.js
@@ -1577,13 +1577,19 @@ var Font = (function FontClosure() {
       return;
     }
 
+    // Some fonts might use wrong font types for Type1C or CIDFontType0C
+    var subtype = properties.subtype;
+    if (subtype == 'Type1C' && (type != 'Type1' && type != 'MMType1'))
+      type = 'Type1';
+    if (subtype == 'CIDFontType0C' && type != 'CIDFontType0')
+      type = 'CIDFontType0';
+
     var data;
     switch (type) {
       case 'Type1':
       case 'CIDFontType0':
         this.mimetype = 'font/opentype';
 
-        var subtype = properties.subtype;
         var cff = (subtype == 'Type1C' || subtype == 'CIDFontType0C') ?
           new CFFFont(file, properties) : new Type1Font(name, file, properties);
 
@@ -2938,6 +2944,7 @@ var Font = (function FontClosure() {
         }
         this.toFontChar = toFontChar;
       }
+      var unitsPerEm = properties.unitsPerEm || 1000; // defaulting to 1000
 
       var fields = {
         // PostScript Font Program
@@ -2958,7 +2965,7 @@ var Font = (function FontClosure() {
               '\x00\x00\x00\x00' + // checksumAdjustement
               '\x5F\x0F\x3C\xF5' + // magicNumber
               '\x00\x00' + // Flags
-              '\x03\xE8' + // unitsPerEM (defaulting to 1000)
+              safeString16(unitsPerEm) + // unitsPerEM
               '\x00\x00\x00\x00\x9e\x0b\x7e\x27' + // creation date
               '\x00\x00\x00\x00\x9e\x0b\x7e\x27' + // modifification date
               '\x00\x00' + // xMin
@@ -3309,6 +3316,20 @@ var Font = (function FontClosure() {
   return Font;
 })();
 
+var ErrorFont = (function ErrorFontClosure() {
+  function ErrorFont(error) {
+    this.error = error;
+  }
+
+  ErrorFont.prototype = {
+    charsToGlyphs: function ErrorFont_charsToGlyphs() {
+      return [];
+    }
+  };
+
+  return ErrorFont;
+})();
+
 var CallothersubrCmd = (function CallothersubrCmdClosure() {
   function CallothersubrCmd(index) {
     this.index = index;
@@ -4413,6 +4434,19 @@ var CFFParser = (function CFFParserClosure() {
       var charStringOffset = topDict.getByName('CharStrings');
       cff.charStrings = this.parseCharStrings(charStringOffset);
 
+      var fontMatrix = topDict.getByName('FontMatrix');
+      if (fontMatrix) {
+        // estimating unitsPerEM for the font
+        properties.unitsPerEm = 1 / fontMatrix[0];
+      }
+
+      var fontBBox = topDict.getByName('FontBBox');
+      if (fontBBox) {
+        // adjusting ascent/descent
+        properties.ascent = fontBBox[3];
+        properties.descent = fontBBox[1];
+      }
+
       var charset, encoding;
       if (cff.isCIDFont) {
         var fdArrayIndex = this.parseIndex(topDict.getByName('FDArray')).obj;
@@ -4486,7 +4520,7 @@ var CFFParser = (function CFFParserClosure() {
           return parseFloatOperand(pos);
         } else if (value === 28) {
           value = dict[pos++];
-          value = (value << 8) | dict[pos++];
+          value = ((value << 24) | (dict[pos++] << 16)) >> 16;
           return value;
         } else if (value === 29) {
           value = dict[pos++];
diff --git a/src/image.js b/src/image.js
index 59f70f99a..19c66ade2 100644
--- a/src/image.js
+++ b/src/image.js
@@ -97,7 +97,12 @@ var PDFImage = (function PDFImageClosure() {
     if (smask) {
       this.smask = new PDFImage(xref, res, smask, false);
     } else if (mask) {
-      this.mask = new PDFImage(xref, res, mask, false);
+      if (isStream(mask)) {
+        this.mask = new PDFImage(xref, res, mask, false);
+      } else {
+        // Color key mask (just an array).
+        this.mask = mask;
+      }
     }
   }
   /**
@@ -129,11 +134,15 @@ var PDFImage = (function PDFImageClosure() {
       maskPromise.resolve(null);
     } else {
       smaskPromise.resolve(null);
-      if (mask && isStream(mask)) {
-        handleImageData(handler, xref, res, mask, maskPromise);
-      } else if (mask) {
-        TODO('handle color key masking');
-        maskPromise.resolve(null);
+      if (mask) {
+        if (isStream(mask)) {
+          handleImageData(handler, xref, res, mask, maskPromise);
+        } else if (isArray(mask)) {
+          maskPromise.resolve(mask);
+        } else {
+          warn('Unsupported mask format.');
+          maskPromise.resolve(null);
+        }
       } else {
         maskPromise.resolve(null);
       }
@@ -279,7 +288,7 @@ var PDFImage = (function PDFImageClosure() {
       }
       return output;
     },
-    getOpacity: function PDFImage_getOpacity(width, height) {
+    getOpacity: function PDFImage_getOpacity(width, height, image) {
       var smask = this.smask;
       var mask = this.mask;
       var originalWidth = this.width;
@@ -294,18 +303,40 @@ var PDFImage = (function PDFImageClosure() {
         if (sw != width || sh != height)
           buf = PDFImage.resize(buf, smask.bpc, 1, sw, sh, width, height);
       } else if (mask) {
-        var sw = mask.width;
-        var sh = mask.height;
-        buf = new Uint8Array(sw * sh);
-        mask.numComps = 1;
-        mask.fillGrayBuffer(buf);
+        if (mask instanceof PDFImage) {
+          var sw = mask.width;
+          var sh = mask.height;
+          buf = new Uint8Array(sw * sh);
+          mask.numComps = 1;
+          mask.fillGrayBuffer(buf);
 
-        // Need to invert values in buffer
-        for (var i = 0, ii = sw * sh; i < ii; ++i)
-          buf[i] = 255 - buf[i];
+          // Need to invert values in buffer
+          for (var i = 0, ii = sw * sh; i < ii; ++i)
+            buf[i] = 255 - buf[i];
 
-        if (sw != width || sh != height)
-          buf = PDFImage.resize(buf, mask.bpc, 1, sw, sh, width, height);
+          if (sw != width || sh != height)
+            buf = PDFImage.resize(buf, mask.bpc, 1, sw, sh, width, height);
+        } else if (isArray(mask)) {
+          // Color key mask: if any of the compontents are outside the range
+          // then they should be painted.
+          buf = new Uint8Array(width * height);
+          var numComps = this.numComps;
+          for (var i = 0, ii = width * height; i < ii; ++i) {
+            var opacity = 0;
+            var imageOffset = i * numComps;
+            for (var j = 0; j < numComps; ++j) {
+              var color = image[imageOffset + j];
+              var maskOffset = j * 2;
+              if (color < mask[maskOffset] || color > mask[maskOffset + 1]) {
+                opacity = 255;
+                break;
+              }
+            }
+            buf[i] = opacity;
+          }
+        } else {
+          error('Unknown mask format.');
+        }
       } else {
         buf = new Uint8Array(width * height);
         for (var i = 0, ii = width * height; i < ii; ++i)
@@ -357,7 +388,7 @@ var PDFImage = (function PDFImageClosure() {
         comps = PDFImage.resize(comps, this.bpc, 3, originalWidth,
                                 originalHeight, width, height);
       var compsPos = 0;
-      var opacity = this.getOpacity(width, height);
+      var opacity = this.getOpacity(width, height, imgArray);
       var opacityPos = 0;
       var length = width * actualHeight * 4;
 
diff --git a/test/pdfs/colorkeymask.pdf b/test/pdfs/colorkeymask.pdf
new file mode 100644
index 000000000..a056d9cbc
Binary files /dev/null and b/test/pdfs/colorkeymask.pdf differ
diff --git a/test/pdfs/issue1810.pdf.link b/test/pdfs/issue1810.pdf.link
index b8689c298..8c84c7505 100644
--- a/test/pdfs/issue1810.pdf.link
+++ b/test/pdfs/issue1810.pdf.link
@@ -1 +1 @@
-http://www.freepatentsonline.com/pdf/documents/uspt/D661/USD661296/USD661296S1.pdf
+http://assets.sbnation.com/assets/1167519/USD661296S1.pdf
diff --git a/test/test_manifest.json b/test/test_manifest.json
index a80c7bb4f..d19633947 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -673,5 +673,11 @@
       "md5": "2ac7c68e26a8ef797aead15e4875cc6d",
       "rounds": 1,
       "type": "load"
+    },
+    {  "id": "colorkeymask",
+      "file": "pdfs/colorkeymask.pdf",
+      "md5": "9f11e815b485f7f0e1fa5c116c636cf9",
+      "rounds": 1,
+      "type": "eq"
     }
 ]
diff --git a/test/unit/font_spec.js b/test/unit/font_spec.js
index 9f0969324..b2436778d 100644
--- a/test/unit/font_spec.js
+++ b/test/unit/font_spec.js
@@ -42,7 +42,7 @@ describe('font', function() {
   }
 
   describe('CFFParser', function() {
-    var parser = new CFFParser(fontData);
+    var parser = new CFFParser(fontData, {});
     var cff = parser.parse();
 
     it('parses header', function() {