Hull Convex

This function block calculates a convex enclosing contour around a provided contour and returns visual and numeric results useful for shape analysis.

📥 Inputs

Image The source image used for visualization and measurements.

Contour The input contour (shape) to enclose with a convex hull.

📤 Outputs

Image The source image annotated with the original contour and its convex hull.

Contour The calculated convex hull contour returned as a shape.

Center The centroid position of the convex hull (x, y).

Area The area of the convex hull.

🕹️ Controls

This function block has no interactive controls. It runs automatically when inputs are provided.

🎯 What it does

• Computes an enclosing convex hull for the provided contour.

• Draws both the original contour and the convex hull onto the image for clear visual comparison.

• Calculates the hull area and its centroid coordinates for downstream measurements or logic.

• Returns both annotated visual output and structured shape/measurement outputs for further processing.

📝 Usage Instructions

1. Provide the original image into the Image input so the block can produce an annotated visual result.

2. Provide a detected contour into the Contour input to compute its convex hull.

3. Use the returned Image to preview hull vs original contour, use Contour/Center/Area for measurements, filtering, or reporting.

📊 Evaluation

When run, the block examines the provided contour, produces a convex hull shape, annotates the image with both shapes, computes the hull centroid and area, and outputs these four results: annotated image, hull contour, center point, and area.

💡 Tips and Tricks

• If you don't yet have a contour, use the Find Contour block or Find Object block to get contours from an image before feeding them into this block.

• To simplify complex contours before hull calculation, consider Approximate Contour to reduce point count and improve performance.

• Use Minimum Rectangle, Minimum Circle, or Minimum Ellipse after this block when you need alternative enclosing shapes or additional geometric descriptors.

• Preprocess the image with Image Threshold, Image Adaptive Threshold, or Blur to get cleaner contours for more reliable hull computation.

• Crop or focus analysis using Image ROI, Image ROI Select, or Image ROI Polygon so the contour extraction and hull calculation target the area of interest.

• Visualize results in a larger window using Show Image and save important frames with Image Logger or Image Write for documentation or offline review.

🛠️ Troubleshooting

• If the output Contour is empty or the Area is zero: ensure the input Contour is valid and contains enough points. Use contour-producing blocks (Find Contour, Find Object) and verify their outputs.

• If annotations look misplaced after image scaling: ensure the same image dimensions are used throughout the pipeline (use Image Resize or Image Resizer consistently).

• If unwanted background shapes produce large hulls: try preprocessing (thresholding, blurring) and use ROI blocks to focus on the object of interest.