diff --git a/.ruby-version b/.ruby-version
index bc4abe8..6a6a3d8 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-2.3.8
+2.6.1
diff --git a/Rakefile b/Rakefile
index a8de4c0..df43bbd 100644
--- a/Rakefile
+++ b/Rakefile
@@ -9,3 +9,9 @@ begin
 rescue LoadError
   # no rspec available
 end
+
+require 'rake/extensiontask'
+
+Rake::ExtensionTask.new('rszr') do |ext|
+  ext.lib_dir = 'lib/rszr'
+end
diff --git a/benchmark/memory.rb b/benchmark/memory.rb
new file mode 100644
index 0000000..3ceee10
--- /dev/null
+++ b/benchmark/memory.rb
@@ -0,0 +1,40 @@
+require 'memory_profiler'
+require 'rszr'
+require 'mini_magick'
+require 'gd2-ffij'
+
+ITERATIONS = 100
+
+original = Pathname.new(__FILE__).dirname.join('../spec/images/test.jpg')
+resized = Pathname.new(__FILE__).dirname.join('output.jpg')
+
+mini_magick = MemoryProfiler.report do
+  ITERATIONS.times do
+    image = MiniMagick::Image.open(original.to_s)
+    image.resize '800x532'
+    image.write resized.to_s
+    image = nil
+  end
+end
+
+mini_magick.pretty_print(scale_bytes: true)
+
+gd2 = MemoryProfiler.report do
+  image = GD2::Image.import(original.to_s)
+  image.resize! 800, 532
+  image.export resized.to_s
+  image = nil
+end
+
+gd2.pretty_print(scale_bytes: true)
+
+rszr = MemoryProfiler.report do
+  ITERATIONS.times do
+    image = Rszr::Image.load(original.to_s)
+    image.resize! 800, 532
+    image.save resized.to_s
+    image = nil
+  end
+end
+
+rszr.pretty_print(scale_bytes: true)
diff --git a/benchmark/benchmark.rb b/benchmark/speed.rb
similarity index 93%
rename from benchmark/benchmark.rb
rename to benchmark/speed.rb
index 539a4e8..8230d90 100644
--- a/benchmark/benchmark.rb
+++ b/benchmark/speed.rb
@@ -14,14 +14,16 @@
       image = MiniMagick::Image.open(original.to_s)
       image.resize '800x532'
       image.write resized.to_s
+      image = nil
     end
   end
-
+  
   x.report 'GD2' do
     ITERATIONS.times do
       image = GD2::Image.import(original.to_s)
       image.resize! 800, 532
       image.export resized.to_s
+      image = nil
     end
   end
   
@@ -30,6 +32,7 @@
       image = Rszr::Image.load(original.to_s)
       image.resize! 800, 532
       image.save resized.to_s
+      image = nil
     end
   end
 end
diff --git a/ext/rszr/errors.c b/ext/rszr/errors.c
new file mode 100644
index 0000000..c1714e0
--- /dev/null
+++ b/ext/rszr/errors.c
@@ -0,0 +1,63 @@
+#ifndef RUBY_RSZR_ERRORS
+#define RUBY_RSZR_ERRORS
+
+#include "rszr.h"
+#include "errors.h"
+
+VALUE eRszrError = Qnil;
+VALUE eRszrFileNotFound = Qnil;
+VALUE eRszrTransformationError = Qnil;
+VALUE eRszrErrorWithMessage = Qnil;
+VALUE eRszrLoadError = Qnil;
+VALUE eRszrSaveError = Qnil;
+
+static const char * const sRszrErrorMessages[] =
+{
+  "File does not exist",
+  "File is a directory",
+  "Read permission denied",
+  "Unsupported format",
+  "Path too long",
+  "Non-existant path component",
+  "Path component is not a directory",
+  "Path outside address space",
+  "Too many symbolic links",
+  "Out of memory",
+  "Out of file descriptors",
+  "Write permission denied",
+  "Out of disk space",
+  "Unknown error"
+};
+const int RSZR_MAX_ERROR_INDEX = 13;
+
+void Init_rszr_errors()
+{
+  eRszrError = rb_define_class_under(mRszr, "Error", rb_eStandardError);
+  eRszrFileNotFound = rb_define_class_under(mRszr, "FileNotFound", eRszrError);
+  eRszrTransformationError = rb_define_class_under(mRszr, "TransformationError", eRszrError);
+  eRszrErrorWithMessage = rb_define_class_under(mRszr, "ErrorWithMessage", eRszrError);
+  eRszrLoadError = rb_define_class_under(mRszr, "LoadError", eRszrErrorWithMessage);
+  eRszrSaveError = rb_define_class_under(mRszr, "SaveError", eRszrErrorWithMessage);
+}
+
+static void rszr_raise_error_with_message(VALUE rb_error_class, Imlib_Load_Error error)
+{
+  int error_index = (int) error - 1;
+  if (error_index < 1 || error_index > RSZR_MAX_ERROR_INDEX)
+    error_index = 13;
+  VALUE rb_error = rb_exc_new2(rb_error_class, sRszrErrorMessages[error_index]);
+  rb_exc_raise(rb_error);
+}
+
+void rszr_raise_load_error(Imlib_Load_Error error)
+{
+  rszr_raise_error_with_message(eRszrLoadError, error);
+}
+
+void rszr_raise_save_error(Imlib_Load_Error error)
+{
+  rszr_raise_error_with_message(eRszrSaveError, error);
+}
+
+
+#endif
\ No newline at end of file
diff --git a/ext/rszr/errors.h b/ext/rszr/errors.h
new file mode 100644
index 0000000..872b68c
--- /dev/null
+++ b/ext/rszr/errors.h
@@ -0,0 +1,15 @@
+#ifndef RUBY_RSZR_ERRORS_H
+#define RUBY_RSZR_ERRORS_H
+
+void Init_rszr_errors();
+void rszr_raise_load_error(Imlib_Load_Error error);
+void rszr_raise_save_error(Imlib_Load_Error error);
+
+extern VALUE eRszrError;
+extern VALUE eRszrFileNotFound;
+extern VALUE eRszrTransformationError;
+extern VALUE eRszrErrorWithMessage;
+extern VALUE eRszrLoadError;
+extern VALUE eRszrSaveError;
+
+#endif
diff --git a/ext/rszr/extconf.rb b/ext/rszr/extconf.rb
new file mode 100644
index 0000000..c00700b
--- /dev/null
+++ b/ext/rszr/extconf.rb
@@ -0,0 +1,37 @@
+require 'mkmf'
+require 'rbconfig'
+=begin
+LIBDIR      = RbConfig::CONFIG['libdir']
+INCLUDEDIR  = RbConfig::CONFIG['includedir']
+
+HEADER_DIRS = [
+  '/opt/local/include',
+  '/usr/local/include',
+  INCLUDEDIR,
+  '/usr/include',
+]
+
+LIB_DIRS = [
+  '/opt/local/lib',
+  '/usr/local/lib',
+  LIBDIR,
+  '/usr/lib',
+]
+
+dir_config('Imlib2', HEADER_DIRS, LIB_DIRS)
+=end
+imlib2_config = with_config('imlib2-config', 'imlib2-config')
+
+$CFLAGS << ' -DX_DISPLAY_MISSING ' << `#{imlib2_config} --cflags`.chomp
+$LDFLAGS << ' ' << `#{imlib2_config} --libs`.chomp
+$LDFLAGS.gsub!(/\ -lX11\ -lXext/, '') if RUBY_PLATFORM =~ /darwin/
+
+unless find_header('Imlib2.h')
+  abort 'imlib2 development headers are missing'
+end
+
+unless find_library('imlib2', 'imlib_set_cache_size')
+  abort 'imlib2 is missing'
+end
+
+create_makefile 'rszr'
diff --git a/ext/rszr/image.c b/ext/rszr/image.c
new file mode 100644
index 0000000..7c38591
--- /dev/null
+++ b/ext/rszr/image.c
@@ -0,0 +1,245 @@
+#ifndef RUBY_RSZR_IMAGE
+#define RUBY_RSZR_IMAGE
+
+#include "rszr.h"
+#include "image.h"
+#include "errors.h"
+
+VALUE cImage = Qnil;
+
+static void rszr_free_image(Imlib_Image image)
+{
+  imlib_context_set_image(image);
+  imlib_free_image();
+}
+
+static void rszr_image_deallocate(rszr_image_handle * handle)
+{
+  // fprintf(stderr, "rszr_image_deallocate");
+  if (handle->image) {
+    // fprintf(stderr, ": freeing");
+    rszr_free_image(handle->image);
+    handle->image = NULL;
+  }
+  free(handle);
+  // fprintf(stderr, "\n");
+}
+
+static VALUE rszr_image_s_allocate(VALUE klass)
+{
+  rszr_image_handle * handle = calloc(1, sizeof(rszr_image_handle));
+  return Data_Wrap_Struct(klass, NULL, rszr_image_deallocate, handle);
+}
+
+static VALUE rszr_image_initialize(VALUE self, VALUE rb_width, VALUE rb_height)
+{
+  rszr_image_handle * handle;
+  
+  Check_Type(rb_width,  T_FIXNUM);
+  Check_Type(rb_height, T_FIXNUM);
+
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  handle->image = imlib_create_image(FIX2INT(rb_width), FIX2INT(rb_height));
+
+  return self;
+}
+
+static VALUE rszr_image_s__load(VALUE klass, VALUE rb_path)
+{
+  rszr_image_handle * handle;
+  Imlib_Image image;
+  char * path;
+  Imlib_Load_Error error;
+  VALUE oImage;
+  
+  path = StringValueCStr(rb_path);
+
+  imlib_set_cache_size(0);
+  image = imlib_load_image_with_error_return(path, &error);
+  
+  if (!image) {
+    rszr_raise_load_error(error);
+    return Qnil;
+  }
+  
+  oImage = rszr_image_s_allocate(cImage);
+  Data_Get_Struct(oImage, rszr_image_handle, handle);
+  handle->image = image;
+  return oImage;
+}
+
+static VALUE rszr_image_format(VALUE self)
+{
+  rszr_image_handle * handle;
+  char * format;
+  
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  imlib_context_set_image(handle->image);
+  format = imlib_image_format();
+  
+  if (format) {
+    return rb_str_new2(format);
+  } else {
+    return Qnil;
+  }
+}
+
+static VALUE rszr_image_width(VALUE self)
+{
+  rszr_image_handle * handle;
+  int width;
+  
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  imlib_context_set_image(handle->image);
+  width = imlib_image_get_width();
+  
+  return INT2NUM(width);
+}
+
+static VALUE rszr_image_height(VALUE self)
+{
+  rszr_image_handle * handle;
+  int height;
+  
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  imlib_context_set_image(handle->image);
+  height = imlib_image_get_height();
+  
+  return INT2NUM(height);
+}
+
+/*
+static VALUE rszr_image_replace(VALUE self, VALUE rb_other)
+{
+  rszr_image_handle * handle;
+  rszr_image_handle * other_handle;
+  
+  if (CLASS_OF(rb_other) != cImage) {
+    rb_raise(rb_eArgError, "Rszr::Image required, got %s", rb_obj_classname(rb_other));
+  }
+  
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  Data_Get_Struct(rb_other, rszr_image_handle, other_handle);
+  
+  return self;
+}
+*/
+
+/*
+static VALUE rszr_image_turn(VALUE self, VALUE orientation)
+{
+  // void imlib_image_orientate(int orientation)
+  return self;
+}
+*/
+
+static Imlib_Image rszr_create_cropped_scaled_image(VALUE self, VALUE rb_src_x, VALUE rb_src_y, VALUE rb_src_w, VALUE rb_src_h, VALUE rb_dst_w, VALUE rb_dst_h)
+{
+  rszr_image_handle * handle;
+  Imlib_Image resized_image;
+  
+  int src_x = NUM2INT(rb_src_x);
+  int src_y = NUM2INT(rb_src_y);
+  int src_w = NUM2INT(rb_src_w);
+  int src_h = NUM2INT(rb_src_h);
+  int dst_w = NUM2INT(rb_dst_w);
+  int dst_h = NUM2INT(rb_dst_h);
+
+  // TODO: raise if <= 0
+
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  imlib_context_set_image(handle->image);
+  imlib_context_set_anti_alias(1);
+  resized_image = imlib_create_cropped_scaled_image(src_x, src_y, src_w, src_h, dst_w, dst_h);
+  
+  if (!resized_image) {
+    rb_raise(eRszrTransformationError, "error resizing image");
+    return NULL;
+  }
+  
+  return resized_image;
+}
+
+static VALUE rszr_image__resize_bang(VALUE self, VALUE rb_src_x, VALUE rb_src_y, VALUE rb_src_w, VALUE rb_src_h, VALUE rb_dst_w, VALUE rb_dst_h)
+{
+  rszr_image_handle * handle;
+  Imlib_Image resized_image;
+
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  resized_image = rszr_create_cropped_scaled_image(self, rb_src_x, rb_src_y, rb_src_w, rb_src_h, rb_dst_w, rb_dst_h);
+  if (!resized_image) return Qfalse;
+  
+  rszr_free_image(handle->image);
+  handle->image = resized_image;
+  
+  return self;
+}
+
+static VALUE rszr_image__resize(VALUE self, VALUE rb_src_x, VALUE rb_src_y, VALUE rb_src_w, VALUE rb_src_h, VALUE rb_dst_w, VALUE rb_dst_h)
+{
+  rszr_image_handle * handle;
+  Imlib_Image resized_image;
+  rszr_image_handle * resized_handle;
+  VALUE oResizedImage;
+
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  resized_image = rszr_create_cropped_scaled_image(self, rb_src_x, rb_src_y, rb_src_w, rb_src_h, rb_dst_w, rb_dst_h);
+  if (!resized_image) return Qfalse;
+  
+  oResizedImage = rszr_image_s_allocate(cImage);
+  Data_Get_Struct(oResizedImage, rszr_image_handle, resized_handle);
+  resized_handle->image = resized_image;
+  
+  return oResizedImage;
+}
+
+static VALUE rszr_image__save(VALUE self, VALUE rb_path, VALUE rb_format)
+{
+  rszr_image_handle * handle;
+  char * path;
+  char * format;
+  Imlib_Load_Error save_error;
+  
+  path = StringValueCStr(rb_path);
+  format = StringValueCStr(rb_format);
+  
+  Data_Get_Struct(self, rszr_image_handle, handle);
+  
+  imlib_context_set_image(handle->image);
+  imlib_image_set_format(format);
+  imlib_save_image_with_error_return(path, &save_error);
+  
+  if (save_error) {
+    rszr_raise_save_error(save_error);
+    return Qfalse;
+  }
+  
+  return Qtrue;
+}
+
+void Init_rszr_image()
+{
+  cImage = rb_define_class_under(mRszr, "Image", rb_cObject);
+  rb_define_alloc_func(cImage, rszr_image_s_allocate);
+
+  // Class methods
+  rb_define_private_method(rb_singleton_class(cImage), "_load", rszr_image_s__load, 1);
+
+  // Instance methods
+  rb_define_method(cImage, "initialize",  rszr_image_initialize, 2);
+  rb_define_method(cImage, "width",       rszr_image_width, 0);
+  rb_define_method(cImage, "height",      rszr_image_height, 0);
+  rb_define_method(cImage, "format",      rszr_image_format, 0);
+  rb_define_private_method(cImage, "_resize!", rszr_image__resize, 6);
+  rb_define_private_method(cImage, "_resize",  rszr_image__resize, 6);
+  rb_define_private_method(cImage, "_save",     rszr_image__save, 2);
+}
+
+#endif
diff --git a/ext/rszr/image.h b/ext/rszr/image.h
new file mode 100644
index 0000000..77f6369
--- /dev/null
+++ b/ext/rszr/image.h
@@ -0,0 +1,12 @@
+#ifndef RUBY_RSZR_IMAGE_H
+#define RUBY_RSZR_IMAGE_H
+
+typedef struct {
+  Imlib_Image image;
+} rszr_image_handle;
+
+extern VALUE cImage;
+
+void Init_rszr_image();
+
+#endif
diff --git a/ext/rszr/rszr.c b/ext/rszr/rszr.c
new file mode 100644
index 0000000..0fe4196
--- /dev/null
+++ b/ext/rszr/rszr.c
@@ -0,0 +1,17 @@
+#ifndef RUBY_RSZR
+#define RUBY_RSZR
+
+#include "rszr.h"
+#include "image.h"
+#include "errors.h"
+
+VALUE mRszr = Qnil;
+
+void Init_rszr()
+{
+    mRszr = rb_define_module("Rszr");
+    Init_rszr_errors();
+    Init_rszr_image();
+}
+
+#endif
diff --git a/ext/rszr/rszr.h b/ext/rszr/rszr.h
new file mode 100644
index 0000000..796945f
--- /dev/null
+++ b/ext/rszr/rszr.h
@@ -0,0 +1,10 @@
+#ifndef RUBY_RSZR_H
+#define RUBY_RSZR_H
+
+#include "ruby.h"
+#include <Imlib2.h>
+
+extern VALUE mRszr;
+void Init_rszr();
+
+#endif
diff --git a/lib/rszr.rb b/lib/rszr.rb
index d05cf90..a8afbfd 100644
--- a/lib/rszr.rb
+++ b/lib/rszr.rb
@@ -1,12 +1,6 @@
-require 'fiddle'
-require 'fiddle/import'
 require 'rbconfig'
 require 'pathname'
 
+require 'rszr/rszr'
 require 'rszr/version'
-require 'rszr/errors'
-require 'rszr/lib'
-require 'rszr/lock'
-require 'rszr/handle'
-require 'rszr/base'
 require 'rszr/image'
diff --git a/lib/rszr/base.rb b/lib/rszr/base.rb
deleted file mode 100644
index 8ad2ca2..0000000
--- a/lib/rszr/base.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-module Rszr
-  module Base
-    
-    def self.included(base)
-      Rszr::Lib.delegate(base)
-      Rszr::Lib.delegate(base.singleton_class)
-      base.include(Lock)
-      base.extend(Lock)
-    end
-    
-    protected
-    
-    def handle
-      @handle
-    end
-    
-    def ptr
-      @handle.ptr
-    end
-    
-    private
-    
-    def assert_valid_keys(hsh, *valid_keys)
-      if unknown_key = (hsh.keys - valid_keys).first
-        raise ArgumentError.new("Unknown key: #{unknown_key.inspect}. Valid keys are: #{valid_keys.map(&:inspect).join(', ')}")
-      end
-    end
-  end
-end
diff --git a/lib/rszr/errors.rb b/lib/rszr/errors.rb
deleted file mode 100644
index 1b08d7d..0000000
--- a/lib/rszr/errors.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-module Rszr
-  class Error < StandardError; end
-
-  class ErrorWithMessage < Error
-    MESSAGES = [nil,
-                'File does not exist',
-                'File is a directory',
-                'Read permission denied',
-                'Unsupported format',
-                'Path too long',
-                'Non-existant path component',
-                'Path component is not a directory',
-                'Path outside address space',
-                'Too many symbolic links',
-                'Out of memory',
-                'Out of file descriptors',
-                'Write permission denied',
-                'Out of disk space',
-                'Unknown error']
-    
-    attr_reader :ptr
-    
-    def initialize
-      @ptr = Fiddle::Pointer.malloc(Rszr::Lib.sizeof('Imlib_Load_Error'))
-    end
-    
-    def error?
-      return if ptr.null?
-      0 != ptr[0]
-    end
-    
-    def message
-      MESSAGES[ptr[0]] unless ptr.null?
-    end
-  end
-
-  
-  class FileNotFound < Error; end
-  class LoadError < ErrorWithMessage; end
-  class TransformationError < Error; end
-  class SaveError < ErrorWithMessage; end
-end
\ No newline at end of file
diff --git a/lib/rszr/handle.rb b/lib/rszr/handle.rb
deleted file mode 100644
index 87ec565..0000000
--- a/lib/rszr/handle.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-module Rszr
-  class Handle
-    attr_reader :ptr, :klass
-    
-    def initialize(obj, ptr)
-      @ptr = ptr
-      raise ArgumentError, "#{obj.class.inspect} does not define the finalize class method" unless obj.class.respond_to?(:finalize, true)
-      @klass = obj.class
-      ObjectSpace.define_finalizer(obj, self)
-    end
-    
-    def replace!(other_ptr)
-      raise ArgumentError, "Cannot replace pointer with itself" if ptr == other_ptr
-      finalize!
-      @ptr = other_ptr
-    end
-    
-    def finalize!(*args)
-      #puts "Finalizing #{args.inspect} #{ptr.inspect}"
-      if !ptr.null? && klass
-        #puts "  calling #{args.inspect}"
-        klass.send(:finalize, ptr)
-        @ptr = Fiddle::Pointer.new(0)
-      #else
-        #puts "  skipping #{args.inspect}"
-      end
-    end
-    
-    def release!
-      replace! Fiddle::Pointer.new(0)
-    end
-    
-    def call(object_id)
-      finalize!(object_id)
-    end
-  end
-end
diff --git a/lib/rszr/image.rb b/lib/rszr/image.rb
index 6fa46a0..c257b3a 100644
--- a/lib/rszr/image.rb
+++ b/lib/rszr/image.rb
@@ -1,95 +1,46 @@
 module Rszr
   class Image
-    include Base
 
     class << self
       
-      alias_method :instantiate, :new
-      protected :instantiate
-      
-      def new(width, height)
-        ptr = with_lock { imlib_create_image(width, height) }
-        raise Error, 'Could not instantiate image' if ptr.null?
-        instantiate(ptr)
-      end
-            
       def load(path, options = {})
         path = path.to_s
         raise FileNotFound unless File.exist?(path)
-        load_error = LoadError.new
-        ptr = with_lock do
-          imlib_set_cache_size(0)
-          imlib_load_image_with_error_return(path, load_error.ptr)
-        end
-        raise load_error, load_error.message if ptr.null?
-        return instantiate(ptr)
+        _load(path)
       end
       alias :open :load
       
-      protected
-      
-      def finalize(ptr)
-        with_lock do
-          imlib_context_set_image(ptr)
-          imlib_free_image
-        end
-      end
-      
-    end
-    
-    def initialize(ptr)
-      @handle = Handle.new(self, ptr)
-    end
-    
-    def width
-      with_image { imlib_image_get_width }
     end
-    
-    def height
-      with_image { imlib_image_get_height }
-    end
-    
+
     def dimensions
       [width, height]
     end
-    
-    def format
-      str_ptr = with_image { imlib_image_format }
-      return if str_ptr.null?
-      str_ptr.to_s
+
+    def inspect
+      fmt = format
+      fmt = " #{fmt.upcase}" if fmt
+      "#<#{self.class.name}:0x#{object_id.to_s(16)} #{width}x#{height}#{fmt}>"
     end
-    
+
     def resize(*args)
-      instantiate(create_resized_image(*args))
+      _resize(*calculate_size(*args))
     end
-    
+
     def resize!(*args)
-      handle.replace!(create_resized_image(*args))
-      self
-    end
-    
-    def crop(*args)
-      instantiate(create_cropped_image(*args))
-    end
-    
-    def crop!(*args)
-      handle.replace!(create_cropped_image(*args))
-      self
+      _resize!(*calculate_size(*args))
     end
+
+    #def crop(*args)
+    #  #instantiate(create_cropped_image(*args))
+    #end
+
+    #def crop!(*args)
+    #  #replace!(create_cropped_image(*args))
+    #end
     
     def save(path, format = nil)
-      with_image do
-        format ||= format_from_filename(path) || 'jpg'
-        imlib_image_set_format(format)
-        save_error = SaveError.new
-        imlib_save_image_with_error_return(path, save_error.ptr)
-        raise save_error, save_error.message if save_error.error?
-        true
-      end
-    end
-    
-    def inspect
-      "#<#{self.class.name}:0x#{object_id.to_s(16)} width=#{width} height=#{height} format=#{format.inspect}>"
+      format ||= format_from_filename(path) || 'jpg'
+      _save(path.to_s, format.to_s)
     end
     
     private
@@ -102,7 +53,7 @@ def inspect
     # 400, 300, background: rgba
     # 400, 300, aspect: false
     
-    def create_resized_image(*args)
+    def calculate_size(*args)
       options = args.last.is_a?(Hash) ? args.pop : {}
       assert_valid_keys options, :crop, :background, :skew  #:extend, :width, :height, :max_width, :max_height, :box
       original_width, original_height = width, height
@@ -142,38 +93,24 @@ def create_resized_image(*args)
       else
         raise ArgumentError, "wrong number of arguments (#{args.size} for 1..2)"
       end
-      resized_ptr = with_image do
-        imlib_context_set_anti_alias(1)
-        imlib_create_cropped_scaled_image(x, y, imlib_image_get_width, imlib_image_get_height, new_width.round, new_height.round)
-      end
-      raise TransformationError, "error resizing image" if resized_ptr.null?
-      resized_ptr
-    end
-    
-    def create_cropped_image(x, y, width, height)
-      cropped_ptr = with_image { imlib_create_cropped_image(x, y, width, height) }
-      raise TransformationError, 'error cropping image' if cropped_ptr.null?
-      cropped_ptr
+      [x, y, original_width, original_height, new_width.round, new_height.round]
     end
     
     def format_from_filename(path)
       File.extname(path)[1..-1]
     end
-    
-    def context_set_image
-      imlib_context_set_image(ptr)
-    end
-    
-    def with_image
-      with_lock do
-        context_set_image
-        yield
+
+    def assert_valid_keys(hsh, *valid_keys)
+      if unknown_key = (hsh.keys - valid_keys).first
+        raise ArgumentError.new("Unknown key: #{unknown_key.inspect}. Valid keys are: #{valid_keys.map(&:inspect).join(', ')}")
       end
     end
     
-    def instantiate(ptr)
-      self.class.send(:instantiate, ptr)
-    end
-    
+    #def create_cropped_image(x, y, width, height)
+    #  cropped_ptr = with_image { imlib_create_cropped_image(x, y, width, height) }
+    #  raise TransformationError, 'error cropping image' if cropped_ptr.null?
+    #  cropped_ptr
+    #end
+
   end
 end
diff --git a/rszr.gemspec b/rszr.gemspec
index 5d11ae5..62a8712 100644
--- a/rszr.gemspec
+++ b/rszr.gemspec
@@ -1,4 +1,3 @@
-# coding: utf-8
 lib = File.expand_path('../lib', __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'rszr/version'
@@ -11,17 +10,19 @@ Gem::Specification.new do |s|
 
   s.summary       = %q{Fast image resizer}
   s.description   = %q{Fast image resizer - do one thing and do it fast.}
-  s.licenses      = ['MIT']
-  s.homepage      = "https://github.com/mtgrosser/rszr"
+  s.licenses      = %w[MIT]
+  s.homepage      = 'https://github.com/mtgrosser/rszr'
 
   s.files         = Dir['{lib}/**/*.rb', 'LICENSE', 'README.md', 'Rakefile']
-  s.require_paths = ["lib"]
+  s.require_paths = %w[lib ext]
 
-  s.add_development_dependency "bundler", "~> 1.9"
-  s.add_development_dependency "rake", "~> 10.0"
-  s.add_development_dependency "byebug"
-  s.add_development_dependency "rspec"
-  s.add_development_dependency "simplecov"
-  s.add_development_dependency "gd2-ffij"
-  s.add_development_dependency "mini_magick"
+  s.add_development_dependency 'bundler', '~> 1.9'
+  s.add_development_dependency 'rake', '~> 10.0'
+  s.add_development_dependency 'rake-compiler'
+  s.add_development_dependency 'byebug'
+  s.add_development_dependency 'rspec'
+  s.add_development_dependency 'simplecov'
+  s.add_development_dependency 'gd2-ffij'
+  s.add_development_dependency 'mini_magick'
+  s.add_development_dependency 'memory_profiler'
 end
diff --git a/spec/rszr_spec.rb b/spec/rszr_spec.rb
index df050dd..817e87c 100644
--- a/spec/rszr_spec.rb
+++ b/spec/rszr_spec.rb
@@ -142,11 +142,11 @@
   context 'Garbage collection' do
     
     it 'releases instances' do
-      GC.start
+      10.times { GC.start(full_mark: true, immediate_sweep: true); sleep 0.5; print '.' }
       expect(ObjectSpace.each_object(Rszr::Image).count).to eq(0)
       20.times { Rszr::Image.load(RSpec.root.join('images/bacon.png')) }
       expect(ObjectSpace.each_object(Rszr::Image).count).to be > 0
-      GC.start
+      5.times { GC.start(full_mark: true, immediate_sweep: true); sleep 0.5; print '.' }
       expect(ObjectSpace.each_object(Rszr::Image).count).to eq(0)
     end
     
@@ -159,26 +159,26 @@ def data
     end
 
     def resize
-      image = nil
-      Tempfile.open('src') do |file|
-        file.binmode
-        file.write data
-        image = Rszr::Image.load(file.path)
-        file.close(true)
-      end
-      image.resize!(200, :auto)
-      Tempfile.open('dst') do |file|
-        image.save(file.path)
-        file.close(true)
+      Tempfile.open('src') do |src_file|
+        src_file.binmode
+        src_file.write data
+        Rszr::Image.open(src_file.path) do |image|
+          image.resize!(200, :auto)
+          Tempfile.open('dst') do |dst_file|
+            image.save(dst_file.path)
+            dst_file.close(true)
+          end
+        end
+        src_file.close(true)
       end
     end
 
-    it 'synchronizes access to imlib2 context' do
+    it 'synchronizes access to imlib2 context by GIL' do
       threads = []
       10.times do |t|
         threads << Thread.new do
-          100.times do |i|
-            print '.' # puts "    #{t}/#{i}"
+          1000.times do |i|
+            print '.'
             resize
           end
         end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 45bd4c2..ba950b6 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -88,4 +88,4 @@
   def self.root
     @spec_root ||= Pathname.new(__FILE__).dirname
   end
-end
\ No newline at end of file
+end