FEATURE: enforce jpg/png for all images

This ensures webp / gif are converted to png prior to sending
to LLMs given webp and gif are not evenly supported.

png/jpg is universally supported and are the only supported format.

longer term we need to add support for audio/video/pdf which is supported by some models.

Author: SamSaffron

lib/completions/upload_encoder.rb

@@ -10,6 +10,14 @@ def self.encode(upload_ids:, max_pixels:)
           next if upload.blank?
           next if upload.width.to_i == 0 || upload.height.to_i == 0
 
+          desired_extension = upload.extension
+          desired_extension = "png" if upload.extension == "gif"
+          desired_extension = "png" if upload.extension == "webp"
+          desired_extension = "jpeg" if upload.extension == "jpg"
+
+          # this keeps it very simple format wise given everyone supports png and jpg
+          next if !%w[jpeg png].include?(desired_extension)
+
           original_pixels = upload.width * upload.height
 
           image = upload
@@ -20,12 +28,15 @@ def self.encode(upload_ids:, max_pixels:)
             new_width = (ratio * upload.width).to_i
             new_height = (ratio * upload.height).to_i
 
-            image = upload.get_optimized_image(new_width, new_height)
+            image = upload.get_optimized_image(new_width, new_height, format: desired_extension)
+          elsif upload.extension != desired_extension
+            image =
+              upload.get_optimized_image(upload.width, upload.height, format: desired_extension)
           end
 
           next if !image
 
-          mime_type = MiniMime.lookup_by_filename(upload.original_filename).content_type
+          mime_type = MiniMime.lookup_by_filename("test.#{desired_extension}").content_type
 
           path = Discourse.store.path_for(image)
           if path.blank?

spec/fixtures/images/1x1.gif

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+RSpec.describe DiscourseAi::Completions::UploadEncoder do
+  let(:file) { plugin_file_from_fixtures("1x1.gif") }
+
+  it "automatically converts gifs to pngs" do
+    upload = UploadCreator.new(file, "1x1.gif").create_for(Discourse.system_user.id)
+    encoded = described_class.encode(upload_ids: [upload.id], max_pixels: 1_048_576)
+    expect(encoded.length).to eq(1)
+    expect(encoded[0][:base64]).to be_present
+    expect(encoded[0][:mime_type]).to eq("image/png")
+  end
+end