Support for the image mask in higher resolution than the image itself

src/core/image.js

@@ -228,14 +228,14 @@ var PDFImage = (function PDFImageClosure() {
 
   PDFImage.prototype = {
     get drawWidth() {
-      if (!this.smask)
-        return this.width;
-      return Math.max(this.width, this.smask.width);
+      return Math.max(this.width,
+                      this.smask && this.smask.width || 0,
+                      this.mask && this.mask.width || 0);
     },
     get drawHeight() {
-      if (!this.smask)
-        return this.height;
-      return Math.max(this.height, this.smask.height);
+      return Math.max(this.height,
+                      this.smask && this.smask.height || 0,
+                      this.mask && this.mask.height || 0);
     },
     decodeBuffer: function PDFImage_decodeBuffer(buffer) {
       var bpc = this.bpc;

test/pdfs/.gitignore

@@ -66,3 +66,4 @@
 !bug946506.pdf
 !issue3885.pdf
 !bug859204.pdf
+!issue4246.pdf

test/test_manifest.json

@@ -1561,5 +1561,12 @@
        "firstPage": 4,
        "lastPage": 4,
        "type": "eq"
+    },
+    {  "id": "issue4246",
+      "file": "pdfs/issue4246.pdf",
+      "md5": "ed81787b83cc317c9f049643b853bea3",
+      "rounds": 1,
+      "type": "eq",
+      "about": "Image mask in higher resolution than the image itself"
     }
 ]