diff --git a/lib/writeexcel/image.rb b/lib/writeexcel/image.rb
index f138ef89..34563377 100644
--- a/lib/writeexcel/image.rb
+++ b/lib/writeexcel/image.rb
@@ -59,11 +59,11 @@ def store_image_record(i, num_images, num_charts, num_filters, num_comments, spi
     # Process the image and extract dimensions.
     def process
       case filetype
-      when 'PNG'
+      when 'png'
         process_png(@data)
-      when 'JPG'
+      when 'jpg', 'jpeg'
         process_jpg(@data)
-      when 'BMP'
+      when 'bmp'
         process_bmp(@data)
         # The 14 byte header of the BMP is stripped off.
         @data[0, 13] = ''
@@ -75,13 +75,7 @@ def process
     end
 
     def filetype
-      return 'PNG' if @data.unpack('x A3')[0] ==  'PNG'
-      return 'BMP' if @data.unpack('A2')[0] == 'BM'
-      if data.unpack('n')[0] == 0xFFD8
-        return 'JPG' if @data.unpack('x6 A4')[0] == 'JFIF' || @data.unpack('x6 A4')[0] == 'Exif'
-      else
-        raise "Unsupported image format for file: #{@filename}\n"
-      end
+      MimeMagic.by_magic(@data).subtype
     end
 
     # Extract width and height information from a PNG file.
diff --git a/test/helper.rb b/test/helper.rb
index 85ba04cc..ce2059c6 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # require 'simplecov'
 require 'test/unit'
-
+require 'mimemagic'
 # SimpleCov.start
 
 $LOAD_PATH.unshift(File.dirname(__FILE__))
diff --git a/test/republic_ps.jpg b/test/republic_ps.jpg
new file mode 100644
index 00000000..d1e106fe
Binary files /dev/null and b/test/republic_ps.jpg differ
diff --git a/test/test_image.rb b/test/test_image.rb
new file mode 100644
index 00000000..3498815d
--- /dev/null
+++ b/test/test_image.rb
@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+require 'helper'
+
+class TestImage < Test::Unit::TestCase
+  def setup
+    @test_file = StringIO.new
+    @workbook = WriteExcel.new(@test_file)
+    @worksheet = @workbook.add_worksheet('test', 0)
+  end
+
+  def test_import_image_is_created_by_adobe_photoshop
+    image = Writeexcel::Image.new(@worksheet, 0, 0, "test/republic_ps.jpg")
+    image.import
+    assert_equal(image.height, 120)
+    assert_equal(image.width, 120)
+    assert_equal(image.size, 24972)
+  end
+end
diff --git a/writeexcel.gemspec b/writeexcel.gemspec
index f2348c89..ad97b65f 100644
--- a/writeexcel.gemspec
+++ b/writeexcel.gemspec
@@ -24,4 +24,5 @@ Gem::Specification.new do |gem|
     "README.rdoc"
   ]
   gem.add_development_dependency 'simplecov'
+  gem.add_development_dependency 'mimemagic'
 end