diff --git a/.rubocop.yml b/.rubocop.yml
index 091f612..e146555 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -15,9 +15,6 @@ Layout/CaseIndentation:
 Layout/EndAlignment:
   EnforcedStyleAlignWith: variable
 
-Layout/FirstHashElementIndentation:
-  EnforcedStyle: consistent
-
 Layout/LineLength:
   Max: 120
 
@@ -25,9 +22,6 @@ Layout/SpaceBeforeBlockBraces:
   EnforcedStyle: no_space
   EnforcedStyleForEmptyBraces: no_space
 
-Lint/PercentStringArray: # broken in rubocop 0.55.0
-  Enabled: false
-
 Metrics/BlockLength:
   Exclude:
     - 'spec/**/*.rb'
@@ -41,39 +35,18 @@ Metrics/MethodLength:
 Naming/MethodParameterName:
   Enabled: false
 
-Style/AccessorGrouping:
-  Enabled: false
-
 Style/Alias:
   EnforcedStyle: prefer_alias_method
 
-Style/EmptyCaseCondition:
-  Enabled: false
-
-Style/Encoding:
-  Enabled: false
-
-Style/FileRead:
+Style/ArgumentsForwarding:
   Enabled: false
 
-Style/HashEachMethods:
-  Enabled: true
-
-Style/HashTransformKeys:
-  Enabled: false
-
-Style/HashTransformValues:
-  Enabled: false
-
-Style/IfUnlessModifier:
+Style/EmptyCaseCondition:
   Enabled: false
 
 Style/NumericPredicate:
   Enabled: false
 
-Style/ParallelAssignment:
-  Enabled: false
-
 Style/SafeNavigation:
   Enabled: false
 
diff --git a/lib/image_size.rb b/lib/image_size.rb
index a881e7f..7fd6a0f 100644
--- a/lib/image_size.rb
+++ b/lib/image_size.rb
@@ -150,17 +150,13 @@ def size_of_gif(ir)
   end
 
   def size_of_mng(ir)
-    unless ir[12, 4] == 'MHDR'
-      raise FormatError, 'MHDR not in place for MNG'
-    end
+    raise FormatError, 'MHDR not in place for MNG' unless ir[12, 4] == 'MHDR'
 
     ir.unpack(16, 8, 'NN')
   end
 
   def size_of_png(ir)
-    unless ir[12, 4] == 'IHDR'
-      raise FormatError, 'IHDR not in place for PNG'
-    end
+    raise FormatError, 'IHDR not in place for PNG' unless ir[12, 4] == 'IHDR'
 
     ir.unpack(16, 8, 'NN')
   end
@@ -178,14 +174,12 @@ def size_of_jpeg(ir)
     loop do
       offset += 1 until [nil, section_marker].include? ir[offset, 1]
       offset += 1 until section_marker != ir[offset + 1, 1]
-      raise FormatError, 'EOF in JPEG' if ir[offset, 1].nil?
+      raise FormatError, 'EOF in JPEG' unless ir[offset, 1]
 
       code, length = ir.unpack(offset, 4, 'xCn')
       offset += 4
 
-      if JPEG_CODE_CHECK.include?(code)
-        return ir.unpack(offset + 1, 4, 'nn').reverse
-      end
+      return ir.unpack(offset + 1, 4, 'nn').reverse if JPEG_CODE_CHECK.include?(code)
 
       offset += length - 2
     end
@@ -250,9 +244,7 @@ def size_of_xbm(ir)
   def size_of_xpm(ir)
     length = 1024
     until (data = ir[0, length]) =~ /"\s*(\d+)\s+(\d+)(\s+\d+\s+\d+){1,2}\s*"/m
-      if data.length != length
-        raise FormatError, 'XPM size not found'
-      end
+      raise FormatError, 'XPM size not found' if data.length != length
 
       length += 1024
     end
@@ -281,7 +273,7 @@ def size_of_tiff(ir)
       tag, type = ifd.unpack(endian2b * 2)
       offset += 12
 
-      next if packspec[type].nil?
+      next unless packspec[type]
 
       value = ifd[8, 4].unpack(packspec[type])[0]
       case tag
diff --git a/spec/image_size/chunky_reader_spec.rb b/spec/image_size/chunky_reader_spec.rb
index 5322033..51e27a8 100644
--- a/spec/image_size/chunky_reader_spec.rb
+++ b/spec/image_size/chunky_reader_spec.rb
@@ -29,7 +29,7 @@ def chunk_size
     {
       'empty string' => '',
       'a bit of data' => 'foo bar baz',
-      'a lot of data' => File.open('GPL', 'rb', &:read),
+      'a lot of data' => File.binread('GPL'),
     }.each do |data_description, data|
       {
         'default' => test_reader.new(data),
diff --git a/spec/image_size_spec.rb b/spec/image_size_spec.rb
index 3561ecf..892c58a 100644
--- a/spec/image_size_spec.rb
+++ b/spec/image_size_spec.rb
@@ -62,8 +62,11 @@ def supported_formats
     describe "for #{path}" do
       let(:name){ File.basename(path) }
       let(:attributes) do
-        match = /(\d+)x(\d+)\.([^.]+)$/.match(name)
-        width, height, format = match[1].to_i, match[2].to_i, match[3].to_sym if match
+        if (match = /(\d+)x(\d+)\.([^.]+)$/.match(name))
+          width = match[1].to_i
+          height = match[2].to_i
+          format = match[3].to_sym
+        end
         size = format && [width, height]
         media_types = ImageSize::MEDIA_TYPES[format] || []
         media_type = format && media_types.first.to_s
@@ -78,7 +81,7 @@ def supported_formats
           media_types: media_types,
         }
       end
-      let(:file_data){ File.open(path, 'rb', &:read) }
+      let(:file_data){ File.binread(path) }
       let(:file_size){ file_data.length }
 
       before do