Fix paint not working with OpenRouter provider (#513)

lib/ruby_llm/providers/openrouter.rb

@@ -5,6 +5,7 @@ module Providers
     # OpenRouter API integration.
     class OpenRouter < OpenAI
       include OpenRouter::Models
+      include OpenRouter::Images
 
       def api_base
         'https://openrouter.ai/api/v1'

lib/ruby_llm/providers/openrouter/images.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+module RubyLLM
+  module Providers
+    class OpenRouter
+      # Image generation methods for the OpenRouter API integration.
+      # OpenRouter uses the chat completions endpoint for image generation
+      # instead of a dedicated images endpoint.
+      module Images
+        module_function
+
+        def images_url
+          'chat/completions'
+        end
+
+        def render_image_payload(prompt, model:, size:)
+          RubyLLM.logger.debug "Ignoring size #{size}. OpenRouter image generation does not support size parameter."
+          {
+            model: model,
+            messages: [
+              {
+                role: 'user',
+                content: prompt
+              }
+            ],
+            modalities: %w[image text]
+          }
+        end
+
+        def parse_image_response(response, model:)
+          data = response.body
+          message = data.dig('choices', 0, 'message')
+
+          unless message&.key?('images') && message['images']&.any?
+            raise Error.new(nil, 'Unexpected response format from OpenRouter image generation API')
+          end
+
+          image_data = message['images'].first
+          image_url = image_data.dig('image_url', 'url') || image_data['url']
+
+          raise Error.new(nil, 'No image URL found in OpenRouter response') unless image_url
+
+          build_image_from_url(image_url, model)
+        end
+
+        def build_image_from_url(image_url, model)
+          if image_url.start_with?('data:')
+            # Parse data URL format: data:image/png;base64,<data>
+            match = image_url.match(/^data:([^;]+);base64,(.+)$/)
+            raise Error.new(nil, 'Invalid data URL format from OpenRouter') unless match
+
+            Image.new(
+              data: match[2],
+              mime_type: match[1],
+              model_id: model
+            )
+          else
+            # Regular URL
+            Image.new(
+              url: image_url,
+              mime_type: 'image/png',
+              model_id: model
+            )
+          end
+        end
+      end
+    end
+  end
+end

spec/ruby_llm/image_generation_spec.rb

@@ -75,5 +75,21 @@ def save_and_verify_image(image)
 
       save_and_verify_image image
     end
+
+    it 'openrouter/google/gemini-2.5-flash-image-preview can paint images' do
+      image = RubyLLM.paint(
+        'a siamese cat',
+        model: 'google/gemini-2.5-flash-image-preview',
+        provider: :openrouter,
+        assume_model_exists: true
+      )
+
+      expect(image.base64?).to be(true)
+      expect(image.data).to be_present
+      expect(image.mime_type).to include('image')
+      expect(image.model_id).to eq('google/gemini-2.5-flash-image-preview')
+
+      save_and_verify_image image
+    end
   end
 end

spec/ruby_llm/providers/open_router/images_spec.rb

@@ -0,0 +1,180 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe RubyLLM::Providers::OpenRouter::Images do
+  let(:images_module) { described_class }
+
+  describe '.images_url' do
+    it 'returns the chat completions endpoint' do
+      expect(images_module.images_url).to eq('chat/completions')
+    end
+  end
+
+  describe '.render_image_payload' do
+    it 'renders a chat completion payload with image modality' do
+      payload = images_module.render_image_payload('a cute cat', model: 'test-model', size: '1024x1024')
+
+      expect(payload[:model]).to eq('test-model')
+      expect(payload[:messages]).to eq([{ role: 'user', content: 'a cute cat' }])
+      expect(payload[:modalities]).to eq(%w[image text])
+    end
+
+    it 'ignores size parameter and logs debug message' do
+      allow(RubyLLM.logger).to receive(:debug)
+      images_module.render_image_payload('a cute cat', model: 'test-model', size: '512x512')
+      expect(RubyLLM.logger).to have_received(:debug).with(/Ignoring size/)
+    end
+  end
+
+  describe '.parse_image_response' do
+    context 'with base64 data URL response' do
+      let(:response_body) do
+        {
+          'choices' => [{
+            'message' => {
+              'role' => 'assistant',
+              'content' => 'Here is an image of a cat',
+              'images' => [{
+                'type' => 'image_url',
+                'image_url' => {
+                  'url' => 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAE='
+                }
+              }]
+            }
+          }]
+        }
+      end
+      let(:response) { instance_double(Faraday::Response, body: response_body) }
+
+      it 'parses base64 image data from response' do
+        image = images_module.parse_image_response(response, model: 'test-model')
+
+        expect(image).to be_a(RubyLLM::Image)
+        expect(image.base64?).to be(true)
+        expect(image.data).to eq('iVBORw0KGgoAAAANSUhEUgAAAAE=')
+        expect(image.mime_type).to eq('image/png')
+        expect(image.model_id).to eq('test-model')
+      end
+    end
+
+    context 'with jpeg image data URL' do
+      let(:response_body) do
+        {
+          'choices' => [{
+            'message' => {
+              'images' => [{
+                'image_url' => { 'url' => 'data:image/jpeg;base64,/9j/4AAQSkZJRg==' }
+              }]
+            }
+          }]
+        }
+      end
+      let(:response) { instance_double(Faraday::Response, body: response_body) }
+
+      it 'parses jpeg image data' do
+        image = images_module.parse_image_response(response, model: 'test-model')
+
+        expect(image.mime_type).to eq('image/jpeg')
+        expect(image.data).to eq('/9j/4AAQSkZJRg==')
+      end
+    end
+
+    context 'with direct url field (alternative format)' do
+      let(:response_body) do
+        {
+          'choices' => [{
+            'message' => {
+              'images' => [{ 'url' => 'data:image/png;base64,abc123' }]
+            }
+          }]
+        }
+      end
+      let(:response) { instance_double(Faraday::Response, body: response_body) }
+
+      it 'parses image from direct url field' do
+        image = images_module.parse_image_response(response, model: 'test-model')
+
+        expect(image.data).to eq('abc123')
+      end
+    end
+
+    context 'with regular URL response' do
+      let(:response_body) do
+        {
+          'choices' => [{
+            'message' => {
+              'images' => [{
+                'image_url' => { 'url' => 'https://example.com/image.png' }
+              }]
+            }
+          }]
+        }
+      end
+      let(:response) { instance_double(Faraday::Response, body: response_body) }
+
+      it 'creates image with URL instead of base64 data' do
+        image = images_module.parse_image_response(response, model: 'test-model')
+
+        expect(image.base64?).to be(false)
+        expect(image.url).to eq('https://example.com/image.png')
+        expect(image.mime_type).to eq('image/png')
+      end
+    end
+
+    context 'with missing images in response' do
+      let(:response_body) do
+        {
+          'choices' => [{
+            'message' => { 'content' => 'Sorry, I cannot generate images' }
+          }]
+        }
+      end
+      let(:response) { instance_double(Faraday::Response, body: response_body) }
+
+      it 'raises an error' do
+        expect do
+          images_module.parse_image_response(response, model: 'test-model')
+        end.to raise_error(RubyLLM::Error, /Unexpected response format/)
+      end
+    end
+
+    context 'with empty images array' do
+      let(:response_body) do
+        {
+          'choices' => [{
+            'message' => { 'images' => [] }
+          }]
+        }
+      end
+      let(:response) { instance_double(Faraday::Response, body: response_body) }
+
+      it 'raises an error' do
+        expect do
+          images_module.parse_image_response(response, model: 'test-model')
+        end.to raise_error(RubyLLM::Error, /Unexpected response format/)
+      end
+    end
+
+    context 'with invalid data URL format' do
+      let(:response_body) do
+        {
+          'choices' => [{
+            'message' => {
+              'images' => [{
+                'image_url' => { 'url' => 'data:invalid-format' }
+              }]
+            }
+          }]
+        }
+      end
+      let(:response) { instance_double(Faraday::Response, body: response_body) }
+
+      it 'raises an error for invalid data URL' do
+        expect do
+          images_module.parse_image_response(response, model: 'test-model')
+        end.to raise_error(RubyLLM::Error, /Invalid data URL format/)
+      end
+    end
+  end
+end