Add basic support for the DDS file format

Readme.md

@@ -18,6 +18,7 @@ A [Node](https://nodejs.org/en/) module to get dimensions of any image file
 * TIFF
 * WebP
 * SVG
+* DDS
 
 ### Upcoming
 

lib/types.js

@@ -8,5 +8,6 @@ module.exports = [
   'psd',
   'svg',
   'tiff',
-  'webp'
+  'webp',
+  'dds'
 ];

lib/types/dds.js

@@ -0,0 +1,18 @@
+'use strict';
+
+function isDDS(buffer){
+	return buffer.readUInt32LE(0) === 0x20534444;
+}
+
+function calculate(buffer){
+	// read file resolution metadata
+	return {
+		'height': buffer.readUInt32LE(12),
+		'width': buffer.readUInt32LE(16)
+	};
+}
+
+module.exports = {
+	'detect': isDDS,
+	'calculate': calculate
+};

specs/others.spec.js

@@ -72,6 +72,6 @@ describe('Callback function', function () {
 
 describe('.types property', function () {
   it('should expose supported file types', function() {
-    expect(imageSize.types).to.eql(['bmp', 'gif', 'jpg', 'png', 'psd', 'svg', 'tiff', 'webp']);
+    expect(imageSize.types).to.eql(['bmp', 'gif', 'jpg', 'png', 'psd', 'svg', 'tiff', 'webp', 'dds']);
   });
 });