API‐Contour‐Analysis

Contour Analysis

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Namespace: acl::contour

Contour geometry analysis. Input is std::vector<acl::Point2i> (typically produced by findContours).

Tier: Pro+
NEON: none (geometric computation, pure CPP)

Related structs

struct acl::Point2i      { int x, y; };                 // input point type
struct acl::Rect         { int x, y, width, height; };
struct acl::Point2f      { float x, y; };
struct acl::Size2f       { float width, height; };
struct acl::RotatedRect  { Point2f center; Size2f size; float angle; };

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contourArea

Compute polygon area via the Shoelace formula. Tier: Pro+
Channels: N/A (point set)
Inplace: not supported
Types:

Template parameter	Allowed types	Constraint
Input	std::vector<acl::Point2i>	—
Output	double	—

double contourArea(
    const std::vector<acl::Point2i>& contour,
    bool oriented = false);

Parameter	Type	Meaning	Default
contour	point array	Contour (at least 3 points, otherwise returns 0)	—
oriented	bool	true = signed area (positive = counter-clockwise, negative = clockwise); false = absolute value	false

The return value is the area (not an error code).

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arcLength

Contour perimeter (sum of Euclidean distances between consecutive points). Tier: Pro+
Channels: N/A (point set)
Inplace: not supported
Types:

Template parameter	Allowed types	Constraint
Input	std::vector<acl::Point2i>	—
Output	double	—

double arcLength(
    const std::vector<acl::Point2i>& contour,
    bool closed = true);

Parameter	Type	Meaning	Default
closed	bool	true = closed (including last point → first point); false = open	true

The return value is the length (not an error code).

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boundingRect

Compute the axis-aligned bounding rectangle of a contour. Tier: Pro+
Channels: N/A (point set)
Inplace: not supported
Types:

Template parameter	Allowed types	Constraint
Input	std::vector<acl::Point2i>	—
Output	acl::Rect	—

acl::Rect boundingRect(
    const std::vector<acl::Point2i>& contour);

Returns a Rect (not an error code). An empty contour returns Rect(0, 0, 0, 0).

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convexHull

Compute the convex hull using Andrew's monotone chain algorithm. Tier: Pro+
Channels: N/A (point set)
Inplace: not supported
Types:

Template parameter	Allowed types	Constraint
input/output	std::vector<acl::Point2i>	—

int convexHull(
    const std::vector<acl::Point2i>& points,
    std::vector<acl::Point2i>& hull);

The output hull is arranged in counter-clockwise order.

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approxPolyDP

Simplify a polygon (reduce the number of vertices) using the Douglas-Peucker algorithm. Tier: Pro+
Channels: N/A (point set)
Inplace: not supported
Types:

Template parameter	Allowed types	Constraint
input/output	std::vector<acl::Point2i>	—

int approxPolyDP(
    const std::vector<acl::Point2i>& curve,
    std::vector<acl::Point2i>& approx,
    double epsilon,
    bool closed = true);

Parameter	Type	Meaning	Default
epsilon	double	Maximum distance between the original curve and the simplified curve	—
closed	bool	Treat as a closed contour	true

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minAreaRect

Compute the minimum-area rotated bounding rectangle using rotating calipers. Tier: Pro+
Channels: N/A (point set)
Inplace: not supported
Types:

Template parameter	Allowed types	Constraint
Input	std::vector<acl::Point2i>	—
Output	acl::RotatedRect	—

int minAreaRect(
    const std::vector<acl::Point2i>& points,
    acl::RotatedRect& result);

The input requires at least 3 points (0 points returns an error; 1-2 points returns a degenerate Rect).

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fitEllipse

Fit an ellipse via Direct Least Squares; outputs the ellipse's rotated-rectangle description. Tier: Pro+
Channels: N/A (point set)
Inplace: not supported
Types:

Template parameter	Allowed types	Constraint
Input	std::vector<acl::Point2i>	≥5
Output	acl::RotatedRect	—

int fitEllipse(
    const std::vector<acl::Point2i>& points,
    acl::RotatedRect& result);

The input requires at least 5 points.