# AprilTags from camera Utilizes the [AprilTag](https://docs.luxonis.com/software-v3/depthai/depthai-components/nodes/april_tag.md) node to detect apriltag markers on the camera stream at 1080P. It outlines detected tags and their IDs on the screen. Check the [AprilTags on 12MP frames](https://docs.luxonis.com/software-v3/depthai/examples/april_tags/april_tags_12mp.md) example for potentially better detection results. ## Demo This example requires the DepthAI v3 API, see [installation instructions](https://docs.luxonis.com/software-v3/depthai.md). ## Pipeline ### examples/april_tags.pipeline.json ```json {"pipeline": {"connections": [{"node1Id": 0, "node1Output": "0", "node1OutputGroup": "dynamicOutputs", "node2Id": 2, "node2Input": "in", "node2InputGroup": ""}], "globalProperties": {"calibData": null, "cameraTuningBlobSize": null, "cameraTuningBlobUri": "", "leonCssFrequencyHz": 700000000.0, "leonMssFrequencyHz": 700000000.0, "pipelineName": null, "pipelineVersion": null, "sippBufferSize": 18432, "sippDmaBufferSize": 16384, "xlinkChunkSize": -1}, "nodes": [[2, {"alias": "", "id": 2, "ioInfo": [[["", "in"], {"blocking": true, "group": "", "id": 4, "name": "in", "queueSize": 3, "type": 3, "waitForMessage": false}]], "logLevel": 3, "name": "XLinkOut", "parentId": -1, "properties": {"maxFpsLimit": -1.0, "metadataOnly": false, "streamName": "__x_0_dynamicOutputs_0"}}], [0, {"alias": "", "id": 0, "ioInfo": [[["dynamicOutputs", "0"], {"blocking": false, "group": "dynamicOutputs", "id": 3, "name": "0", "queueSize": 8, "type": 0, "waitForMessage": false}], [["", "raw"], {"blocking": false, "group": "", "id": 2, "name": "raw", "queueSize": 8, "type": 0, "waitForMessage": false}], [["", "mockIsp"], {"blocking": true, "group": "", "id": 1, "name": "mockIsp", "queueSize": 8, "type": 3, "waitForMessage": false}], [["", "inputControl"], {"blocking": true, "group": "", "id": 0, "name": "inputControl", "queueSize": 3, "type": 3, "waitForMessage": false}]], "logLevel": 3, "name": "Camera", "parentId": -1, "properties": {"boardSocket": 0, "cameraName": "", "fps": -1.0, "imageOrientation": -1, "initialControl": {"aeLockMode": false, "aeMaxExposureTimeUs": 65544, "aeRegion": {"height": 0, "priority": 0, "width": 0, "x": 0, "y": 0}, "afRegion": {"height": 43, "priority": 131077, "width": 12, "x": 0, "y": 0}, "antiBandingMode": 0, "autoFocusMode": 3, "awbLockMode": false, "awbMode": 0, "brightness": 0, "captureIntent": 0, "chromaDenoise": 136, "cmdMask": 0, "contrast": -116, "controlMode": 12, "effectMode": 0, "enableHdr": false, "expCompensation": 0, "expManual": {"exposureTimeUs": 0, "frameDurationUs": 0, "sensitivityIso": 0}, "frameSyncMode": 6, "lensPosAutoInfinity": 0, "lensPosAutoMacro": 0, "lensPosition": 0, "lensPositionRaw": 0.0, "lowPowerNumFramesBurst": 1, "lowPowerNumFramesDiscard": 0, "lumaDenoise": 0, "miscControls": [], "saturation": 0, "sceneMode": 0, "sharpness": 2, "strobeConfig": {"activeLevel": 110, "enable": 0, "gpioNumber": 111}, "strobeTimings": {"durationUs": 2949132, "exposureBeginOffsetUs": 6649189, "exposureEndOffsetUs": 1704760}, "wbColorTemp": 1}, "isp3aFps": 0, "mockIspHeight": -1, "mockIspWidth": -1, "numFramesPoolIsp": 3, "numFramesPoolPreview": 4, "numFramesPoolRaw": 3, "numFramesPoolStill": 4, "numFramesPoolVideo": 4, "outputRequests": [{"enableUndistortion": null, "fps": {"value": null}, "resizeMode": 0, "size": {"value": {"index": 0, "value": [1920, 1080]}}, "type": null}], "resolutionHeight": -1, "resolutionWidth": -1}}]]}} ``` ## Source code #### Python ```python #!/usr/bin/env python3 import cv2 import depthai as dai import time with dai.Pipeline() as pipeline: hostCamera = pipeline.create(dai.node.Camera).build() aprilTagNode = pipeline.create(dai.node.AprilTag) hostCamera.requestOutput((1920, 1080)).link(aprilTagNode.inputImage) passthroughOutputQueue = aprilTagNode.passthroughInputImage.createOutputQueue() outQueue = aprilTagNode.out.createOutputQueue() color = (0, 255, 0) startTime = time.monotonic() counter = 0 fps = 0.0 pipeline.start() while pipeline.isRunning(): aprilTagMessage = outQueue.get() assert(isinstance(aprilTagMessage, dai.AprilTags)) aprilTags = aprilTagMessage.aprilTags counter += 1 currentTime = time.monotonic() if (currentTime - startTime) > 1: fps = counter / (currentTime - startTime) counter = 0 startTime = currentTime passthroughImage: dai.ImgFrame = passthroughOutputQueue.get() frame = passthroughImage.getCvFrame() def to_int(tag): return (int(tag.x), int(tag.y)) for tag in aprilTags: topLeft = to_int(tag.topLeft) topRight = to_int(tag.topRight) bottomRight = to_int(tag.bottomRight) bottomLeft = to_int(tag.bottomLeft) center = (int((topLeft[0] + bottomRight[0]) / 2), int((topLeft[1] + bottomRight[1]) / 2)) cv2.line(frame, topLeft, topRight, color, 2, cv2.LINE_AA, 0) cv2.line(frame, topRight,bottomRight, color, 2, cv2.LINE_AA, 0) cv2.line(frame, bottomRight,bottomLeft, color, 2, cv2.LINE_AA, 0) cv2.line(frame, bottomLeft,topLeft, color, 2, cv2.LINE_AA, 0) idStr = "ID: " + str(tag.id) cv2.putText(frame, idStr, center, cv2.FONT_HERSHEY_TRIPLEX, 0.5, color) cv2.putText(frame, f"fps: {fps:.1f}", (200, 20), cv2.FONT_HERSHEY_TRIPLEX, 0.5, color) cv2.imshow("detections", frame) if cv2.waitKey(1) == ord("q"): break ``` #### C++ ```cpp #include #include #include #include #include #include #include "depthai/depthai.hpp" std::atomic quitEvent(false); void signalHandler(int) { quitEvent = true; } int main() { signal(SIGTERM, signalHandler); signal(SIGINT, signalHandler); // Create device std::shared_ptr device = std::make_shared(); // Create pipeline dai::Pipeline pipeline(device); // Create nodes auto cameraNode = pipeline.create()->build(); auto aprilTagNode = pipeline.create(); // Configure nodes auto outputCam = cameraNode->requestOutput(std::make_pair(1280, 720)); outputCam->link(aprilTagNode->inputImage); // Create output queues auto passthroughOutputQueue = aprilTagNode->passthroughInputImage.createOutputQueue(); auto outQueue = aprilTagNode->out.createOutputQueue(); // Start pipeline pipeline.start(); // Variables for FPS calculation auto startTime = std::chrono::steady_clock::now(); int counter = 0; float fps = 0.0f; const cv::Scalar color(0, 255, 0); while(pipeline.isRunning() && !quitEvent) { auto aprilTagMessage = outQueue->get(); if(aprilTagMessage == nullptr) continue; // FPS calculation counter++; auto currentTime = std::chrono::steady_clock::now(); auto elapsed = std::chrono::duration_cast(currentTime - startTime).count(); if(elapsed > 1000) { fps = counter * 1000.0f / elapsed; counter = 0; startTime = currentTime; } auto frame = passthroughOutputQueue->get(); if(frame == nullptr) continue; cv::Mat cvFrame = frame->getCvFrame(); // Helper function to convert points to integers auto to_int = [](const dai::Point2f& p) { return cv::Point(static_cast(p.x), static_cast(p.y)); }; for(const auto& tag : aprilTagMessage->aprilTags) { auto topLeft = to_int(tag.topLeft); auto topRight = to_int(tag.topRight); auto bottomRight = to_int(tag.bottomRight); auto bottomLeft = to_int(tag.bottomLeft); cv::Point center((topLeft.x + bottomRight.x) / 2, (topLeft.y + bottomRight.y) / 2); // Draw tag boundaries cv::line(cvFrame, topLeft, topRight, color, 2, cv::LINE_AA, 0); cv::line(cvFrame, topRight, bottomRight, color, 2, cv::LINE_AA, 0); cv::line(cvFrame, bottomRight, bottomLeft, color, 2, cv::LINE_AA, 0); cv::line(cvFrame, bottomLeft, topLeft, color, 2, cv::LINE_AA, 0); // Draw tag ID std::string idStr = "ID: " + std::to_string(tag.id); cv::putText(cvFrame, idStr, center, cv::FONT_HERSHEY_TRIPLEX, 0.5, color); // Draw FPS cv::putText(cvFrame, "fps: " + std::to_string(fps).substr(0, 4), cv::Point(200, 20), cv::FONT_HERSHEY_TRIPLEX, 0.5, color); } cv::imshow("detections", cvFrame); if(cv::waitKey(1) == 'q') { break; } } pipeline.stop(); pipeline.wait(); return 0; } ``` ### Need assistance? 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