# MediaPipe graph that performs object detection with TensorFlow Lite on CPU.
# Used in the examples in
# mediapipe/examples/android/src/java/com/mediapipe/apps/objectdetectioncpu and
# mediapipe/examples/ios/objectdetectioncpu.
# Images on GPU coming into and out of the graph.
input_stream: "input_video"
output_stream: "output_video"
# Transfers the input image from GPU to CPU memory for the purpose of
# demonstrating a CPU-based pipeline. Note that the input image on GPU has the
# origin defined at the bottom-left corner (OpenGL convention). As a result,
# the transferred image on CPU also shares the same representation.
node: {
calculator: "GpuBufferToImageFrameCalculator"
input_stream: "input_video"
output_stream: "input_video_cpu"
}
# Throttles the images flowing downstream for flow control. It passes through
# the very first incoming image unaltered, and waits for
# TfLiteTensorsToDetectionsCalculator downstream in the graph to finish
# generating the corresponding detections before it passes through another
# image. All images that come in while waiting are dropped, limiting the number
# of in-flight images between this calculator and
# TfLiteTensorsToDetectionsCalculator to 1. This prevents the nodes in between
# from queuing up incoming images and data excessively, which leads to increased
# latency and memory usage, unwanted in real-time mobile applications. It also
# eliminates unnecessarily computation, e.g., a transformed image produced by
# ImageTransformationCalculator may get dropped downstream if the subsequent
# TfLiteConverterCalculator or TfLiteInferenceCalculator is still busy
# processing previous inputs.
node {
calculator: "FlowLimiterCalculator"
input_stream: "input_video_cpu"
input_stream: "FINISHED:detections"
input_stream_info: {
tag_index: "FINISHED"
back_edge: true
}
output_stream: "throttled_input_video_cpu"
}
# Transforms the input image on CPU to a 320x320 image. To scale the image, by
# default it uses the STRETCH scale mode that maps the entire input image to the
# entire transformed image. As a result, image aspect ratio may be changed and
# objects in the image may be deformed (stretched or squeezed), but the object
# detection model used in this graph is agnostic to that deformation.
node: {
calculator: "ImageTransformationCalculator"
input_stream: "IMAGE:throttled_input_video_cpu"
output_stream: "IMAGE:transformed_input_video_cpu"
node_options: {
[type.googleapis.com/mediapipe.ImageTransformationCalculatorOptions] {
output_width: 320
output_height: 320
}
}
}
# Converts the transformed input image on CPU into an image tensor stored as a
# TfLiteTensor.
node {
calculator: "TfLiteConverterCalculator"
input_stream: "IMAGE:transformed_input_video_cpu"
output_stream: "TENSORS:image_tensor"
}
# Runs a TensorFlow Lite model on CPU that takes an image tensor and outputs a
# vector of tensors representing, for instance, detection boxes/keypoints and
# scores.
node {
calculator: "TfLiteInferenceCalculator"
input_stream: "TENSORS:image_tensor"
output_stream: "TENSORS:detection_tensors"
node_options: {
[type.googleapis.com/mediapipe.TfLiteInferenceCalculatorOptions] {
model_path: "mediapipe/models/ssdlite_object_detection.tflite"
}
}
}
# Generates a single side packet containing a vector of SSD anchors based on
# the specification in the options.
node {
calculator: "SsdAnchorsCalculator"
output_side_packet: "anchors"
node_options: {
[type.googleapis.com/mediapipe.SsdAnchorsCalculatorOptions] {
num_layers: 6
min_scale: 0.2
max_scale: 0.95
input_size_height: 320
input_size_width: 320
anchor_offset_x: 0.5
anchor_offset_y: 0.5
strides: 16
strides: 32
strides: 64
strides: 128
strides: 256
strides: 512
aspect_ratios: 1.0
aspect_ratios: 2.0
aspect_ratios: 0.5
aspect_ratios: 3.0
aspect_ratios: 0.3333
reduce_boxes_in_lowest_layer: true
}
}
}
# Decodes the detection tensors generated by the TensorFlow Lite model, based on
# the SSD anchors and the specification in the options, into a vector of
# detections. Each detection describes a detected object.
node {
calculator: "TfLiteTensorsToDetectionsCalculator"
input_stream: "TENSORS:detection_tensors"
input_side_packet: "ANCHORS:anchors"
output_stream: "DETECTIONS:detections"
node_options: {
[type.googleapis.com/mediapipe.TfLiteTensorsToDetectionsCalculatorOptions] {
num_classes: 91
num_boxes: 2034
num_coords: 4
ignore_classes: 0
sigmoid_score: true
apply_exponential_on_box_size: true
x_scale: 10.0
y_scale: 10.0
h_scale: 5.0
w_scale: 5.0
min_score_thresh: 0.6
}
}
}
# Performs non-max suppression to remove excessive detections.
node {
calculator: "NonMaxSuppressionCalculator"
input_stream: "detections"
output_stream: "filtered_detections"
node_options: {
[type.googleapis.com/mediapipe.NonMaxSuppressionCalculatorOptions] {
min_suppression_threshold: 0.4
max_num_detections: 3
overlap_type: INTERSECTION_OVER_UNION
return_empty_detections: true
}
}
}
# Maps detection label IDs to the corresponding label text. The label map is
# provided in the label_map_path option.
node {
calculator: "DetectionLabelIdToTextCalculator"
input_stream: "filtered_detections"
output_stream: "output_detections"
node_options: {
[type.googleapis.com/mediapipe.DetectionLabelIdToTextCalculatorOptions] {
label_map_path: "mediapipe/models/ssdlite_object_detection_labelmap.txt"
}
}
}
# Converts the detections to drawing primitives for annotation overlay.
node {
calculator: "DetectionsToRenderDataCalculator"
input_stream: "DETECTIONS:output_detections"
output_stream: "RENDER_DATA:render_data"
node_options: {
[type.googleapis.com/mediapipe.DetectionsToRenderDataCalculatorOptions] {
thickness: 4.0
color { r: 255 g: 0 b: 0 }
}
}
}
# Draws annotations and overlays them on top of the input images.
node {
calculator: "AnnotationOverlayCalculator"
input_stream: "IMAGE:throttled_input_video_cpu"
input_stream: "render_data"
output_stream: "IMAGE:output_video_cpu"
}
# Transfers the annotated image from CPU back to GPU memory, to be sent out of
# the graph.
node: {
calculator: "ImageFrameToGpuBufferCalculator"
input_stream: "output_video_cpu"
output_stream: "output_video"
}
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