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Detections Filter

Class: DetectionsFilterBlockV1

Source: inference.core.workflows.core_steps.transformations.detections_filter.v1.DetectionsFilterBlockV1

Filter detection predictions based on customizable conditions, selectively removing detections that don't meet specified criteria (e.g., class names, confidence scores, bounding box properties) while preserving only the detections that match your filtering logic.

How This Block Works

This block applies conditional filtering to detection predictions using a flexible query language system. The block:

  1. Takes detection predictions (object detection, instance segmentation, or keypoint detection) and filtering operation definitions as input
  2. Evaluates each detection against the filtering conditions specified in the operations parameter
  3. Extracts detection properties (e.g., class_name, confidence, bounding box coordinates) using property extraction operations
  4. Compares extracted properties against criteria using binary statements (e.g., class_name in list, confidence > threshold)
  5. Filters out detections that don't match the conditions, keeping only detections that satisfy the filter criteria
  6. Returns filtered predictions containing only the detections that passed the filter conditions

The block uses a query language system that supports extracting various detection properties (class names, confidence scores, bounding box coordinates, etc.) and applying conditional logic to filter detections. Filtering operations can check if properties are in lists, compare numeric values, check string equality, or use other comparators. The operations_parameters dictionary provides runtime values (like class name lists or thresholds) that are referenced in the filtering operations, allowing dynamic filtering criteria that can change based on workflow inputs or computed values. Multiple filtering operations can be chained together to create complex filtering logic.

Common Use Cases

  • Class-Based Filtering: Filter detections to keep only specific object classes (e.g., keep only "person" and "car" detections, remove all others), enabling focused processing on relevant object types while excluding unwanted detections
  • Confidence Threshold Filtering: Remove low-confidence detections to improve detection quality (e.g., keep detections with confidence > 0.7, filter out uncertain predictions), ensuring downstream processing works with reliable detections
  • Multi-Criteria Filtering: Apply multiple filtering conditions simultaneously (e.g., keep detections where class_name is in allowed list AND confidence > threshold), combining class and confidence filtering for precise control
  • Dynamic Filtering Based on Workflow State: Use workflow inputs or computed values to determine filtering criteria (e.g., filter classes based on user input, adjust confidence threshold based on lighting conditions), enabling adaptive filtering that responds to changing conditions
  • Pre-Processing for Downstream Blocks: Filter detections before passing to visualization, counting, or storage blocks (e.g., remove false positives before counting, filter out background classes before visualization), reducing noise and improving accuracy of subsequent operations
  • Selective Processing Workflows: Route different filtered subsets to different downstream blocks (e.g., filter high-confidence detections to one path, low-confidence to another), enabling conditional processing based on detection quality or type

Connecting to Other Blocks

The filtered predictions from this block can be connected to:

  • Detection model blocks (e.g., Object Detection Model, Instance Segmentation Model, Keypoint Detection Model) to receive predictions that are filtered based on class, confidence, or other properties
  • Visualization blocks (e.g., Bounding Box Visualization, Polygon Visualization, Label Visualization) to display only the filtered detections, reducing visual clutter and focusing on relevant objects
  • Counting and analytics blocks (e.g., Line Counter, Time in Zone, Velocity) to count or analyze only specific filtered classes or confidence levels, ensuring accurate metrics for the objects of interest
  • Data storage blocks (e.g., Local File Sink, CSV Formatter, Roboflow Dataset Upload, Webhook Sink) to save or transmit only filtered detection results, reducing storage and bandwidth usage by excluding irrelevant detections
  • Other transformation blocks (e.g., Detections Merge, Detections Transform, Detection Offset) to apply additional transformations to the filtered subset, enabling complex processing pipelines on filtered detections
  • Flow control blocks (e.g., Continue If, Rate Limiter) to conditionally trigger downstream processing based on whether filtered detections meet certain criteria, enabling conditional workflows based on filtered results

Type identifier

Use the following identifier in step "type" field: roboflow_core/detections_filter@v1to add the block as as step in your workflow.

Properties

Name Type Description Refs
name str Enter a unique identifier for this step.. ❌
operations List[Union[ClassificationPropertyExtract, ConvertDictionaryToJSON, ConvertImageToBase64, ConvertImageToJPEG, DetectionsFilter, DetectionsOffset, DetectionsPropertyExtract, DetectionsRename, DetectionsSelection, DetectionsShift, DetectionsToDictionary, Divide, ExtractDetectionProperty, ExtractFrameMetadata, ExtractImageProperty, LookupTable, Multiply, NumberRound, NumericSequenceAggregate, PickDetectionsByParentClass, RandomNumber, SequenceAggregate, SequenceApply, SequenceElementsCount, SequenceLength, SequenceMap, SortDetections, StringMatches, StringSubSequence, StringToLowerCase, StringToUpperCase, TimestampToISOFormat, ToBoolean, ToNumber, ToString]] Definition of filtering logic using the query language system. Specifies one or more filtering operations (e.g., DetectionsFilter) that use StatementGroup syntax to define conditional logic. Each operation can extract detection properties (class_name, confidence, coordinates, etc.) and compare them using binary statements (e.g., class_name in list, confidence > threshold). Multiple operations can be chained to create complex filtering logic. The operations reference parameter names from operations_parameters to access runtime values.. ❌

The Refs column marks possibility to parametrise the property with dynamic values available in workflow runtime. See Bindings for more info.

Available Connections

Compatible Blocks

Check what blocks you can connect to Detections Filter in version v1.

Input and Output Bindings

The available connections depend on its binding kinds. Check what binding kinds Detections Filter in version v1 has.

Bindings

  • input

    • predictions (Union[instance_segmentation_prediction, object_detection_prediction, keypoint_detection_prediction]): Detection predictions to filter (object detection, instance segmentation, or keypoint detection). Each detection is evaluated against the filtering conditions specified in the operations parameter. Only detections that match the filter criteria are included in the output. Supports batch processing, allowing filtering of multiple detection sets simultaneously..
    • operations_parameters (*): Dictionary mapping parameter names (referenced in operations) to actual values from the workflow. These parameters provide runtime values used in filtering operations (e.g., class name lists, confidence thresholds). Keys match parameter names used in the operations definition, and values are selectors referencing workflow inputs, step outputs, or computed values. Example: {'classes': '$inputs.allowed_classes', 'threshold': 0.7} where 'classes' and 'threshold' are referenced in the operations..

  • output

    • predictions (Union[object_detection_prediction, instance_segmentation_prediction, keypoint_detection_prediction]): Prediction with detected bounding boxes in form of sv.Detections(...) object if object_detection_prediction or Prediction with detected bounding boxes and segmentation masks in form of sv.Detections(...) object if instance_segmentation_prediction or Prediction with detected bounding boxes and detected keypoints in form of sv.Detections(...) object if keypoint_detection_prediction.
Example JSON definition of step Detections Filter in version v1 
{
    "name": "<your_step_name_here>",
    "type": "roboflow_core/detections_filter@v1",
    "predictions": "$steps.object_detection_model.predictions",
    "operations": [
        {
            "filter_operation": {
                "statements": [
                    {
                        "comparator": {
                            "type": "in (Sequence)"
                        },
                        "left_operand": {
                            "operations": [
                                {
                                    "property_name": "class_name",
                                    "type": "ExtractDetectionProperty"
                                }
                            ],
                            "type": "DynamicOperand"
                        },
                        "right_operand": {
                            "operand_name": "classes",
                            "type": "DynamicOperand"
                        },
                        "type": "BinaryStatement"
                    }
                ],
                "type": "StatementGroup"
            },
            "type": "DetectionsFilter"
        }
    ],
    "operations_parameters": {
        "classes": "$inputs.classes"
    }
}