Morphological Operations

Morphological operations are shape-based image transformations that process images using structuring elements. They are commonly used on binary or grayscale images for filtering noise, separating touching elements, or detecting corners.

Key Operations

Dilation

Grows regions of foreground pixels, taking the local maximum value. It expands bright regions in the image.

// Apply dilation with a kernel size of 3
let dilated = image.dilate(3)?;

Erosion

Shrinks regions of foreground pixels, taking the local minimum value. It expands dark regions in the image.

// Apply erosion with a kernel size of 3
let eroded = image.erode(3)?;

Morphological Opening

Erosion followed by dilation. Useful for removing small bright noise objects.

let opened = image.morph_open(3)?;

Morphological Closing

Dilation followed by erosion. Useful for filling small holes or joining segments.

let closed = image.morph_close(3)?;

Morphology Ex

Provides advanced morphological transformations combining dilation and erosion.

• MorphOp::Opening: Erosion followed by dilation.
• MorphOp::Closing: Dilation followed by erosion.
• MorphOp::Gradient: Difference between dilation and erosion. Highlights boundaries.
• MorphOp::TopHat: Difference between input image and opening. Isolates bright features smaller than the kernel.
• MorphOp::BlackHat: Difference between closing and input image. Isolates dark features smaller than the kernel.

let opened = image.morphology_ex(MorphOp::Opening, 3)?;
let gradient = image.morphology_ex(MorphOp::Gradient, 3)?;

Custom Kernels

Dilate / Erode with Custom Kernel

Apply morphological operations with a user-defined binary kernel.

let kernel: Vec<&[u8]> = vec![
    &[0, 1, 0],
    &[1, 1, 1],
    &[0, 1, 0],
];
let dilated = image.dilate_with_kernel(&kernel)?;
let eroded = image.erode_with_kernel(&kernel)?;

Structuring Elements

Structuring elements (or kernels) represent the spatial shapes used during filtering. Iris provides standard pre-built shape models:

• MorphShape::Rect: Flat box elements.
• MorphShape::Cross: Cross-shaped orthogonal lines.
• MorphShape::Ellipse: Elliptical kernel mask.

let size = Size::new(5, 5);
let element = Morphology::get_structuring_element(MorphShape::Ellipse, size);