diff --git a/docs/framework_concepts/graphs.md b/docs/framework_concepts/graphs.md index f951b506d..b20a87467 100644 --- a/docs/framework_concepts/graphs.md +++ b/docs/framework_concepts/graphs.md @@ -143,6 +143,98 @@ Below is an example of how to create a subgraph named `TwoPassThroughSubgraph`. } ``` +## Graph Options + +It is possible to specify a "graph options" protobuf for a MediaPipe graph +similar to the [`Calculator Options`](calculators.md#calculator-options) +protobuf specified for a MediaPipe calculator. These "graph options" can be +specified where a graph is invoked, and used to populate calculator options and +subgraph options within the graph. + +In a CalculatorGraphConfig, graph options can be specified for a subgraph +exactly like calculator options, as shown below: + +``` +node { + calculator: "FlowLimiterCalculator" + input_stream: "image" + output_stream: "throttled_image" + node_options: { + [type.googleapis.com/mediapipe.FlowLimiterCalculatorOptions] { + max_in_flight: 1 + } + } +} + +node { + calculator: "FaceDetectionSubgraph" + input_stream: "IMAGE:throttled_image" + node_options: { + [type.googleapis.com/mediapipe.FaceDetectionOptions] { + tensor_width: 192 + tensor_height: 192 + } + } +} +``` + +In a CalculatorGraphConfig, graph options can be accepted and used to populate +calculator options, as shown below: + +``` +graph_options: { + [type.googleapis.com/mediapipe.FaceDetectionOptions] {} +} + +node: { + calculator: "ImageToTensorCalculator" + input_stream: "IMAGE:multi_backend_image" + node_options: { + [type.googleapis.com/mediapipe.ImageToTensorCalculatorOptions] { + keep_aspect_ratio: true + border_mode: BORDER_ZERO + } + } + option_value: "output_tensor_width:options/tensor_width" + option_value: "output_tensor_height:options/tensor_height" +} + +node { + calculator: "InferenceCalculator" + node_options: { + [type.googleapis.com/mediapipe.InferenceCalculatorOptions] {} + } + option_value: "delegate:options/delegate" + option_value: "model_path:options/model_path" +} +``` + +In this example, the `FaceDetectionSubgraph` accepts graph option protobuf +`FaceDetectionOptions`. The `FaceDetectionOptions` is used to define some field +values in the calculator options `ImageToTensorCalculatorOptions` and some field +values in the subgraph options `InferenceCalculatorOptions`. The field values +are defined using the `option_value:` syntax. + +In the `CalculatorGraphConfig::Node` protobuf, the fields `node_options:` and +`option_value:` together define the option values for a calculator such as +`ImageToTensorCalculator`. The `node_options:` field defines a set of literal +constant values using the text protobuf syntax. Each `option_value:` field +defines the value for one protobuf field using information from the enclosing +graph, specifically from field values of the graph options of the enclosing +graph. In the example above, the `option_value:` +`"output_tensor_width:options/tensor_width"` defines the field +`ImageToTensorCalculatorOptions.output_tensor_width` using the value of +`FaceDetectionOptions.tensor_width`. + +The syntax of `option_value:` is similar to the syntax of `input_stream:`. The +syntax is `option_value: "LHS:RHS"`. The LHS identifies a calculator option +field and the RHS identifies a graph option field. More specifically, the LHS +and RHS each consists of a series of protobuf field names identifying nested +protobuf messages and fields separated by '/'. This is known as the "ProtoPath" +syntax. Nested messages that are referenced in the LHS or RHS must already be +defined in the enclosing protobuf in order to be traversed using +`option_value:`. + ## Cycles