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Cropped ROI Endpoint (Classification Only)

Overview​

The cropped_roi endpoint provides access to cropped Regions of Interest (ROIs) generated from classification results in Haystack running on the device.

Important: This endpoint works only for classification-type results. Segmentation type is not supported for ROI cropping through this endpoint.

The base URL format is:

http://{device-ip}/edge/haystack/cropped_roi/{classification_result_id}

How It Works​

When the camera completes a classification capture, The Node-RED flow dynamically constructs URLs for the cropped ROI images by pairing the device IP and classification result ID:

const imageUrl = `http://${baseUrl}/edge/haystack/cropped_roi/${result.id}`;

Each URL serves a cropped image corresponding to individual classification ROI, typically representing a single inspection.

Node-RED Flow Summary​

The ROI_Crop flow performs the following:

  1. Extracts the Device IP

    • Parses the image_url field to find the IP (e.g., 192.168.0.101)
    • Stores it globally for reuse

  2. Queries Latest Capture Data

    • Sends a GET request to the device’s PostgREST API:

      http://{device-ip}/postgrest/captures?select=...
      &order=id.desc&limit=1

    • Retrieves the most recent capture and all classification_result entries

  3. Filters for Classification Results Only

    • Skips segmentation or alignment results

    • Iterates over each classification result:

      classificationResults.forEach(result => {
        const roiName = result.roi_result?.inspection_region?.name || `ROI_${result.id}`;
        const imageUrl = `http://${baseUrl}/edge/haystack/cropped_roi/${result.id}`;
        imageMap[roiName] = imageUrl;
      });

  4. Outputs the Cropped ROI URLs

    • Saves all ROI image links to a global imageMap
    • Returns the list of latest cropped ROI image URLs

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Example Usage​

Fetch a Cropped ROI Image​

curl http://192.168.0.101/edge/haystack/cropped_roi/42 -o roi_42.jpg

Use in a Web Interface​

<img src="http://192.168.0.101/edge/haystack/cropped_roi/42" alt="Cropped ROI 42">

Output Example​

{
  "ROI_1": "http://192.168.0.101/edge/haystack/cropped_roi/1",
  "ROI_2": "http://192.168.0.101/edge/haystack/cropped_roi/2"
}

Parameters​

ParameterTypeDescription
device-ipstringIP address of the camera (e.g. 192.168.0.101)

Integration Flow​

  1. Acquire latest capture metadata via /postgrest/captures.
  2. Identify available classification_result IDs.
  3. Construct cropped ROI URLs for each result.
  4. Display or download those images for analysis, training data, or QA inspection.

Download Node-RED Flow​

  • ROI Crop Flow (JSON) - Complete Node-RED flow for extracting cropped ROI images
    • Import this flow directly into Node-RED to access cropped classification ROIs
    • Works with both OV20i and OV80i systems