fix: ensure that VipsImageProcessor#write_to_jpeg uses jpg regardless…

… of the output file extension

Since vips chooses format based on the extension, the easiest way to guarantee the expected format is to append .jpg to the filename, then rename

lib/morandi/vips_image_processor.rb

@@ -73,12 +73,14 @@ def write_to_png(_write_to, _orientation = :any)
       raise 'not implemented'
     end
 
-    def write_to_jpeg(write_to, quality = nil)
+    def write_to_jpeg(target_path, quality = nil)
       process!
 
       quality ||= @options.fetch('quality', 97)
 
-      @img.write_to_file(write_to, Q: quality)
+      target_path_jpg = "#{target_path}.jpg" # Vips chooses format based on file extension, this ensures jpg
+      @img.write_to_file(target_path_jpg, Q: quality)
+      FileUtils.mv(target_path_jpg, target_path)
     end
 
     private

spec/morandi_spec.rb

@@ -489,6 +489,16 @@
         end
       end
     end
+
+    context 'with output file having jpg extension' do
+      let(:file_out) { "#{super()}.png" }
+
+      it 'writes file as jpg' do
+        process_image
+
+        expect(processed_image_type).to eq('jpeg')
+      end
+    end
   end
 
   context 'pixbuf processor' do