updated OpenAI to use ContentPart's media option for setting image me…

…dia data when base64 encoded

MODEL_BEHAVIORS.md

@@ -8,4 +8,12 @@ This is to document some of the differences between model behaviors. This is spe
   - 2024-04-17
 
 - Anthropic's Claude 3 does respond well to pre-filled assistant responses and it is officially encouraged.
-  - 2024-04-17
+  - 2024-04-17
+
+## Image content parts
+
+- Anthropic will not work if the media type is included with the base64 data. ie. `"data:image/jpeg;base64," <> "..."`
+  - Requires providing the media type as a separate option.
+- ChatGPT -
+  - When `base64` data given, requires providing the image data prefixed with the base64 content.
+  - Ex: `"data:image/jpeg;base64," <> "..."`

lib/chat_models/chat_open_ai.ex

@@ -239,7 +239,21 @@ defmodule LangChain.ChatModels.ChatOpenAI do
   end
 
   def for_api(%ContentPart{type: image} = part) when image in [:image, :image_url] do
-    %{"type" => "image_url", "image_url" => %{"url" => part.content}}
+    media_prefix =
+      case Keyword.get(part.options || [], :media, nil) do
+        nil ->
+          ""
+
+        type when is_binary(type) ->
+          "data:#{type};base64,"
+
+        other ->
+          message = "Received unsupported media type for ContentPart: #{inspect(other)}"
+          Logger.error(message)
+          raise LangChainError, message
+      end
+
+    %{"type" => "image_url", "image_url" => %{"url" => media_prefix <> part.content}}
   end
 
   # ToolCall support

lib/message/content_part.ex

@@ -84,6 +84,14 @@ defmodule LangChain.Message.ContentPart do
 
   - `:media` - Provide the "media type" for the image. Examples: "image/jpeg",
     "image/png", etc. ChatGPT does not require this but other LLMs may.
+
+  ChatGPT requires media type information to prefix the base64 content. Setting
+  the `media: "image/jpeg"` type will do that. Otherwise the data must be
+  provided with the required prefix.
+
+  Anthropic requires the media type information to be submitted as separate
+  information with the JSON request. This media option provides an abstraction
+  to normalize the behavior.
   """
   @spec image!(String.t(), Keyword.t()) :: t() | no_return()
   def image!(content, opts \\ []) do

test/chat_models/chat_open_ai_test.exs

@@ -177,6 +177,24 @@ defmodule LangChain.ChatModels.ChatOpenAITest do
       assert result == expected
     end
 
+    test "turns an image ContentPart with base64 media into the expected JSON format" do
+      expected = %{
+        "type" => "image_url",
+        "image_url" => %{"url" => "data:image/jpeg;base64,image_base64_data"}
+      }
+
+      result = ChatOpenAI.for_api(ContentPart.image!("image_base64_data", media: "image/jpeg"))
+      assert result == expected
+
+      expected = %{
+        "type" => "image_url",
+        "image_url" => %{"url" => "data:image/png;base64,image_base64_data"}
+      }
+
+      result = ChatOpenAI.for_api(ContentPart.image!("image_base64_data", media: "image/png"))
+      assert result == expected
+    end
+
     test "turns an image_url ContentPart into the expected JSON format" do
       expected = %{"type" => "image_url", "image_url" => %{"url" => "url-to-image"}}
       result = ChatOpenAI.for_api(ContentPart.image_url!("url-to-image"))