Update imgdnn.js

source/imgdnn.js

@@ -7,7 +7,7 @@ imgdnn.ModelFactory = class {
     match(context) {
         const stream = context.stream;
         const signature = [ 0x49, 0x4d, 0x47, 0x44, 0x4e, 0x4e ]; // IMGDNN
-        if (stream.length >= signature.length && stream.peek(4).every((value, index) => value === signature[index])) {
+        if (stream.length >= signature.length && stream.peek(6).every((value, index) => value === signature[index])) {
             return 'imgdnn';
         }
         return undefined;