Merge pull request #2673 from tvdeyen/do-not-remove-background-from-n…

…on-transparent-images

Do not remove background from non transparent images

app/models/alchemy/picture_variant.rb

@@ -14,6 +14,7 @@ class PictureVariant
     include Alchemy::Picture::Transformations
 
     ANIMATED_IMAGE_FORMATS = %w[gif webp]
+    TRANSPARENT_IMAGE_FORMATS = %w[gif webp png]
 
     attr_reader :picture, :render_format
 
@@ -100,7 +101,9 @@ def encoded_image(image, options = {})
       end
 
       if options[:flatten]
-        encoding_options << "-background transparent" if render_format == "png"
+        if render_format.in?(TRANSPARENT_IMAGE_FORMATS) && picture.image_file_format.in?(TRANSPARENT_IMAGE_FORMATS)
+          encoding_options << "-background transparent"
+        end
         encoding_options << "-flatten"
       end
 

config/locales/alchemy.en.yml

@@ -118,7 +118,9 @@ en:
             gif: GIF Image
             jpeg: JPG Image
             png: PNG Image
+            svg: SVG Image
             tiff: TIFF Image
+            webp: WebP Image
         misc:
           name: Miscellaneous
           values:

spec/models/alchemy/picture_variant_spec.rb

@@ -181,6 +181,37 @@
         expect(step.arguments).to eq(["png", "-background transparent -flatten"])
       end
 
+      context "converted to non transparent format" do
+        let(:options) do
+          {format: "jpg"}
+        end
+
+        it "does not add transparent background." do
+          step = subject.steps[0]
+          expect(step.name).to eq(:encode)
+          expect(step.arguments).to eq(["jpg", "-quality 85 -flatten"])
+        end
+      end
+
+      context "converted from non transparent format" do
+        let(:options) do
+          {format: "png", flatten: true}
+        end
+
+        let(:image_file) do
+          fixture_file_upload(
+            File.expand_path("../../fixtures/image4.jpg", __dir__),
+            "image/jpeg"
+          )
+        end
+
+        it "does not add transparent background." do
+          step = subject.steps[0]
+          expect(step.name).to eq(:encode)
+          expect(step.arguments).to eq(["png", "-flatten"])
+        end
+      end
+
       context "converted to webp" do
         let(:options) do
           {format: "webp"}