Replace Phashion with dhash-vips

Phashion currently doesn't install on Apple Silicon, and it doesn't seem
it's going to get fixed.

An upside is that this will now work on JRuby as well, since dhash-vips
doesn't use C extensions.

image_processing.gemspec

@@ -23,5 +23,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "minitest", "~> 5.8"
   spec.add_development_dependency "minitest-hooks", ">= 1.4.2"
   spec.add_development_dependency "minispec-metadata"
-  spec.add_development_dependency "phashion" unless RUBY_ENGINE == "jruby"
+  spec.add_development_dependency "dhash-vips"
 end

test/test_helper.rb

@@ -10,7 +10,7 @@
 
 ENV["VIPS_WARNING"] = "0" # disable libvips warnings
 
-require "phashion" unless RUBY_ENGINE == "jruby"
+require "dhash-vips"
 require "vips"
 require "mini_magick"
 
@@ -27,15 +27,11 @@ def copy_to_tempfile(io, extension = nil)
   end
 
   def assert_similar(image1, image2)
-    return if RUBY_ENGINE == "jruby" # Phashion has C extensions
-
-    assert_operator distance(image1, image2), :<=, 4
+    assert_operator distance(image1, image2), :<=, 3
   end
 
   def refute_similar(image1, image2)
-    return if RUBY_ENGINE == "jruby" # Phashion has C extensions
-
-    assert_operator distance(image1, image2), :>, 4
+    assert_operator distance(image1, image2), :>, 3
   end
 
   def assert_dimensions(dimensions, file)
@@ -49,10 +45,10 @@ def assert_type(type, file)
   private
 
   def distance(image1, image2)
-    a = Phashion::Image.new(image1.path)
-    b = Phashion::Image.new(image2.path)
+    hash1 = DHashVips::IDHash.fingerprint(image1.path)
+    hash2 = DHashVips::IDHash.fingerprint(image2.path)
 
-    a.distance_from(b).abs
+    DHashVips::IDHash.distance hash1, hash2
   end
 end
 

test/vips_test.rb

@@ -295,7 +295,7 @@
     it "produces correct image when enlarging" do
       @pipeline = ImageProcessing::Vips.source(@landscape)
       expected = fixture_image("pad-large.jpg")
-      assert_similar expected, @pipeline.resize_and_pad!(1000, 1000, background: [0, 255, 0])
+      assert_similar expected, @pipeline.resize_and_pad!(1000, 1000, background: [55, 126, 34])
     end
 
     it "accepts gravity" do