Auto Exposure on ROI

This example shows how to dynamically set the Auto Exposure (AE) of the RGB camera dynamically, during application runtime, based on bounding box position.

By default, AutoExposure region is adjusted based on neural network output. If desired, the region can be set manually. You can do so by pressing one of the following buttons:

  • w - move AE region up

  • s - move AE region down

  • a - move AE region left

  • d - move AE region right

  • n - deactivate manual region (switch back to nn-based roi)

Demo

Setup

Please run the install script to download all required dependencies. Please note that this script must be ran from git context, so you have to download the depthai-python repository first and then run the script

git clone https://github.com/luxonis/depthai-python.git
cd depthai-python/examples
python3 install_requirements.py

For additional information, please follow installation guide

This example also requires MobilenetSDD blob (mobilenet-ssd_openvino_2021.2_5shave.blob file) to work - you can download it from here

Source code

Also available on GitHub

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#!/usr/bin/env python3

from pathlib import Path
import sys
import cv2
import depthai as dai
import numpy as np

# Press WASD to move a manual ROI window for auto-exposure control.
# Press N to go back to the region controlled by the NN detections.

# Get argument first
nnPath = str((Path(__file__).parent / Path('models/mobilenet-ssd_openvino_2021.4_6shave.blob')).resolve().absolute())
if len(sys.argv) > 1:
    nnPath = sys.argv[1]

if not Path(nnPath).exists():
    import sys
    raise FileNotFoundError(f'Required file/s not found, please run "{sys.executable} install_requirements.py"')

previewSize = (300, 300)

# Create pipeline
pipeline = dai.Pipeline()

# Define source and outputs
camRgb = pipeline.createColorCamera()
camRgb.setPreviewSize(*previewSize)
camRgb.setInterleaved(False)

camControlIn = pipeline.createXLinkIn()
camControlIn.setStreamName('camControl')
camControlIn.out.link(camRgb.inputControl)

# Define a neural network that will make predictions based on the source frames
nn = pipeline.createMobileNetDetectionNetwork()
nn.setConfidenceThreshold(0.5)
nn.setBlobPath(nnPath)
nn.setNumInferenceThreads(2)
nn.input.setBlocking(False)
camRgb.preview.link(nn.input)

# Linking
xoutRgb = pipeline.createXLinkOut()
xoutRgb.setStreamName("rgb")
camRgb.preview.link(xoutRgb.input)

nnOut = pipeline.createXLinkOut()
nnOut.setStreamName("nn")
nn.out.link(nnOut.input)

# MobilenetSSD label texts
labelMap = ["background", "aeroplane", "bicycle", "bird", "boat", "bottle", "bus", "car", "cat", "chair", "cow",
            "diningtable", "dog", "horse", "motorbike", "person", "pottedplant", "sheep", "sofa", "train", "tvmonitor"]

def clamp(num, v0, v1):
    return max(v0, min(num, v1))

def asControl(roi):
    camControl = dai.CameraControl()
    camControl.setAutoExposureRegion(*roi)
    return camControl

class AutoExposureRegion:
    step = 10
    position = (0, 0)
    size = (100, 100)
    resolution = camRgb.getResolutionSize()
    maxDims = previewSize[0], previewSize[1]

    def grow(self, x=0, y=0):
        self.size = (
            clamp(x + self.size[0], 1, self.maxDims[0]),
            clamp(y + self.size[1], 1, self.maxDims[1])
        )

    def move(self, x=0, y=0):
        self.position = (
            clamp(x + self.position[0], 0, self.maxDims[0]),
            clamp(y + self.position[1], 0, self.maxDims[1])
        )

    def endPosition(self):
        return (
            clamp(self.position[0] + self.size[0], 0, self.maxDims[0]),
            clamp(self.position[1] + self.size[1], 0, self.maxDims[1]),
        )

    def toRoi(self):
        roi = np.array([*self.position, *self.size])
        # Convert to absolute camera coordinates
        roi = roi * self.resolution[1] // 300
        roi[0] += (self.resolution[0] - self.resolution[1]) // 2  # x offset for device crop
        return roi

    @staticmethod
    def bboxToRoi(bbox):
        startX, startY = bbox[:2]
        width, height = bbox[2] - startX, bbox[3] - startY
        roi = frameNorm(np.empty(camRgb.getResolutionSize()), (startX, startY, width, height))
        return roi

# Connect to device and start pipeline
with dai.Device(pipeline) as device:

    # Output queues will be used to get the rgb frames and nn data from the outputs defined above
    qControl = device.getInputQueue(name="camControl")
    qRgb = device.getOutputQueue(name="rgb", maxSize=4, blocking=False)
    qDet = device.getOutputQueue(name="nn", maxSize=4, blocking=False)
    frame = None
    detections = []

    nnRegion = True
    region = AutoExposureRegion()

    # nn data (bounding box locations) are in <0..1> range - they need to be normalized with frame width/height
    def frameNorm(frame, bbox):
        normVals = np.full(len(bbox), frame.shape[0])
        normVals[::2] = frame.shape[1]
        return (np.clip(np.array(bbox), 0, 1) * normVals).astype(int)

    def displayFrame(name, frame):
        for detection in detections:
            bbox = frameNorm(frame, (detection.xmin, detection.ymin, detection.xmax, detection.ymax))
            cv2.rectangle(frame, (bbox[0], bbox[1]), (bbox[2], bbox[3]), (255, 0, 0), 2)
            cv2.putText(frame, labelMap[detection.label], (bbox[0] + 10, bbox[1] + 20), cv2.FONT_HERSHEY_TRIPLEX, 0.5, 255)
            cv2.putText(frame, f"{int(detection.confidence * 100)}%", (bbox[0] + 10, bbox[1] + 40), cv2.FONT_HERSHEY_TRIPLEX, 0.5, 255)
        if not nnRegion:
            cv2.rectangle(frame, region.position, region.endPosition(), (0, 255, 0), 2)
        cv2.imshow(name, frame)

    while True:
        # Instead of get (blocking), we use tryGet (nonblocking) which will return the available data or None otherwise
        inRgb = qRgb.tryGet()
        inDet = qDet.tryGet()

        if inRgb is not None:
            frame = inRgb.getCvFrame()

        if inDet is not None:
            detections = inDet.detections

            if nnRegion and len(detections) > 0:
                bbox = (detections[0].xmin, detections[0].ymin, detections[0].xmax, detections[0].ymax)
                qControl.send(asControl(AutoExposureRegion.bboxToRoi(bbox)))

        if frame is not None:
            displayFrame("rgb", frame)

        key = cv2.waitKey(1)
        if key == ord('n'):
            print("AE ROI controlled by NN")
            nnRegion = True
        elif key in [ord('w'), ord('a'), ord('s'), ord('d'), ord('+'), ord('-')]:
            nnRegion = False
            if key == ord('a'):
                region.move(x=-region.step)
            if key == ord('d'):
                region.move(x=region.step)
            if key == ord('w'):
                region.move(y=-region.step)
            if key == ord('s'):
                region.move(y=region.step)
            if key == ord('+'):
                region.grow(x=10, y=10)
                region.step = region.step + 1
            if key == ord('-'):
                region.grow(x=-10, y=-10)
                region.step = max(region.step - 1, 1)
            print(f"Setting static AE ROI: {region.toRoi()} (on frame: {[*region.position, *region.endPosition()]})")
            qControl.send(asControl(region.toRoi()))
        elif key == ord('q'):
            break

Got questions?

We’re always happy to help with code or other questions you might have.