Histogram On Line

This function block analyzes pixel values along a single defined line in a grayscale or binary image. It detects segments where pixel values exceed a threshold and visualizes the line and found segments on an output image.

📥 Inputs

Input Image (Binary Image) A binary or grayscale image used for line analysis.

📤 Outputs

Output Image The source image annotated with the drawn line and markers for detected peak segments.

Peak Count Number of detected threshold segments along the line.

Peak Start Locations List of start coordinates for each detected segment.

Peak End Locations List of end coordinates for each detected segment.

Peak Mean Locations List of mean (center) coordinates for each detected segment.

🕹️ Controls

Relation Dropdown to choose line orientation (vertical or horizontal).

Line Location Slider / input to pick the pixel position of the line (in pixels). Accepts single value; validated against image size.

Pixel Threshold Slider / input for the pixel value threshold (0–255) used to determine active segments.

🎨 Features

• Visual feedback with a red line and colored markers showing segment start, end, and mean positions.

• Accepts vertical or horizontal lines and validates line location against image dimensions.

• Ignores segments that touch image edges (configurable by internal behavior) to avoid edge artifacts.

• Returns both visual and structured outputs for downstream processing.

📝 Usage Instructions

1. Provide a grayscale or binary image to the Input Image (Binary Image) input.

2. Choose the line orientation using Relation.

3. Set the Line Location (pixel index) within image bounds.

4. Set Pixel Threshold between 0 and 255 to control sensitivity.

5. Run the block to get an annotated image and lists of detected segment coordinates.

📊 Evaluation

On execution, the block samples pixel values along the chosen line, finds contiguous segments where values meet or exceed the threshold, marks them on the output image, and returns the count and coordinate lists.

💡 Tips and Tricks

• Preprocess noisy inputs with Blur to reduce spurious detections and with Image Threshold to create a clean binary image before analyzing a line.

• Use Image ROI Select or Image ROI to crop the region of interest so line coordinates are simpler and more meaningful.

• Combine with Draw Line when you want interactive line placement on the displayed image, then copy the pixel position into Line Location.

• Use HSV Filter to isolate color channels or features before converting to grayscale for more reliable peak detection.

• Inspect results visually by connecting the output image to Show Image so you can open a larger viewer and verify detected segments.

• If your flow may produce empty images, consider Is None to guard downstream logic against missing results.

🛠️ Troubleshooting

• If you get no peaks, try lowering Pixel Threshold or preprocess with Image Threshold / Blur.

• If line position causes errors, ensure Line Location is within image width (for vertical) or height (for horizontal). The block will report and clamp out-of-range values.

• If many tiny segments appear, increase the threshold or smooth the image first with Blur.