Convert non-web image (e.g. PSD) variants to PNG

activestorage/app/models/active_storage/variant.rb

@@ -35,6 +35,8 @@
 #
 #   avatar.variant(resize: "100x100", monochrome: true, flip: "-90")
 class ActiveStorage::Variant
+  WEB_IMAGE_CONTENT_TYPES = %w( image/png image/jpeg image/jpg image/gif )
+
   attr_reader :blob, :variation
   delegate :service, to: :blob
 
@@ -62,7 +64,7 @@ class ActiveStorage::Variant
   # for a variant that points to the ActiveStorage::VariantsController, which in turn will use this +service_call+ method
   # for its redirection.
   def service_url(expires_in: service.url_expires_in, disposition: :inline)
-    service.url key, expires_in: expires_in, disposition: disposition, filename: blob.filename, content_type: blob.content_type
+    service.url key, expires_in: expires_in, disposition: disposition, filename: filename, content_type: content_type
   end
 
   # Returns the receiving variant. Allows ActiveStorage::Variant and ActiveStorage::Preview instances to be used interchangeably.
@@ -76,11 +78,40 @@ class ActiveStorage::Variant
     end
 
     def process
-      service.upload key, transform(service.download(blob.key))
+      service.upload key, transform(blob.download)
     end
 
+
+    def filename
+      if WEB_IMAGE_CONTENT_TYPES.include?(blob.content_type)
+        blob.filename
+      else
+        ActiveStorage::Filename.new("#{blob.filename.base}.png")
+      end
+    end
+
+    def content_type
+      blob.content_type.presence_in(WEB_IMAGE_CONTENT_TYPES) || "image/png"
+    end
+
+
     def transform(io)
+      read_image_from(io) do |image|
+        mogrify image
+        format image
+      end
+    end
+
+    def read_image_from(io, &block)
       require "mini_magick"
-      File.open MiniMagick::Image.read(io).tap { |image| variation.transform(image) }.path
+      File.open MiniMagick::Image.read(io).tap(&block).path
+    end
+
+    def mogrify(image)
+      variation.transform(image)
+    end
+
+    def format(image)
+      image.format("PNG") unless WEB_IMAGE_CONTENT_TYPES.include?(blob.content_type)
     end
 end

activestorage/test/models/variant_test.rb

@@ -4,12 +4,9 @@ require "test_helper"
 require "database/setup"
 
 class ActiveStorage::VariantTest < ActiveSupport::TestCase
-  setup do
-    @blob = create_file_blob filename: "racecar.jpg"
-  end
-
-  test "resized variation" do
-    variant = @blob.variant(resize: "100x100").processed
+  test "resized variation of JPEG blob" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(resize: "100x100").processed
     assert_match(/racecar\.jpg/, variant.service_url)
 
     image = read_image(variant)
@@ -17,8 +14,9 @@ class ActiveStorage::VariantTest < ActiveSupport::TestCase
     assert_equal 67, image.height
   end
 
-  test "resized and monochrome variation" do
-    variant = @blob.variant(resize: "100x100", monochrome: true).processed
+  test "resized and monochrome variation of JPEG blob" do
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(resize: "100x100", monochrome: true).processed
     assert_match(/racecar\.jpg/, variant.service_url)
 
     image = read_image(variant)
@@ -27,6 +25,17 @@ class ActiveStorage::VariantTest < ActiveSupport::TestCase
     assert_match(/Gray/, image.colorspace)
   end
 
+  test "resized variation of PSD blob" do
+    blob = create_file_blob(filename: "icon.psd", content_type: "image/vnd.adobe.photoshop")
+    variant = blob.variant(resize: "20x20").processed
+    assert_match(/icon\.png/, variant.service_url)
+
+    image = read_image(variant)
+    assert_equal "PNG", image.type
+    assert_equal 20, image.width
+    assert_equal 20, image.height
+  end
+
   test "variation of invariable blob" do
     assert_raises ActiveStorage::Blob::InvariableError do
       create_file_blob(filename: "report.pdf", content_type: "application/pdf").variant(resize: "100x100")
@@ -34,7 +43,8 @@ class ActiveStorage::VariantTest < ActiveSupport::TestCase
   end
 
   test "service_url doesn't grow in length despite long variant options" do
-    variant = @blob.variant(font: "a" * 10_000).processed
+    blob = create_file_blob(filename: "racecar.jpg")
+    variant = blob.variant(font: "a" * 10_000).processed
     assert_operator variant.service_url.length, :<, 500
   end
 end