Standard library · Machine learning

opencv

Computer vision with OpenCV: image processing, features, face detection, neural networks and video.

import opencv

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Types
Constants and variables
Functions

This package binds the OpenCV library and gives most of the everyday computer vision work: color conversion, resizing, filters, edge detection and thresholds, contours, ORB and SIFT features, face detection with a cascade classifier, running DNN networks, and reading and writing video and camera frames.

It needs OpenCV and the Salam shim at run time; check with Available that the library was loaded. For simpler work with no dependency, see the image package. The examples on the site are only type-checked.

Types

`VideoCapture`

struct VideoCapture

Reads video or a camera.

Name	Type	Description
`handle`	`void*`	The internal handle.

opencv-Detect.salam

import opencv
import image

func main:
    mut cascade := opencv.LoadCascade("haarcascade_frontalface_default.xml")
    mut photo := opencv.Read("people_en.jpg")
    if cascade.ok():
        each face in cascade.detect(photo.to_gray(), 1.1, 5, 100):
            photo.rectangle(face.x, face.y, face.width, face.height, opencv.Green(), 2)
        end
    end
    cascade.free()

    mut net := opencv.LoadNet("MobileNetSSD_en.caffemodel", "MobileNetSSD_en.prototxt")
    mut single := opencv.LoadNetSingleFile("model_en.onnx")
    if net.ok():
        _ := net.set_input(photo, 0.007843, opencv.RGB(127, 127, 127), false, opencv.Size { width = 300, height = 300 })
        output := net.forward()
        _ := net.forward_layer("detection_out")
        each obj in opencv.ParseSSDDetections(output, photo.width(), photo.height(), 0.5):
            println obj.class_id, obj.confidence, obj.x, obj.y, obj.width, obj.height
        end
    end
    net.free()
    single.free()

    mut video := opencv.OpenVideo("clip_en.mp4")
    mut camera := opencv.OpenCamera(0)
    mut writer := opencv.NewVideoWriter("out_en.mp4", "mp4v", video.fps(), 640, 480)
    println video.ok(), video.frame_count(), camera.ok(), writer.ok()
    opencv.CreateTrackbar("threshold", "preview", 100, 255)
    until video.ok():
        frame := video.read()
        if frame.empty():
            break
        end
        level := opencv.GetTrackbarPos("threshold", "preview")
        edges := frame.to_gray().canny(level as f64, 200.0)
        _ := writer.write(frame)
        opencv.Imshow("preview", edges)
        if opencv.WaitKey(1) == 27:
            break
        end
    end
    opencv.SetTrackbarPos("threshold", "preview", 50)
    opencv.DestroyWindow("preview")
    opencv.DestroyAllWindows()
    video.close()
    camera.close()
    writer.close()

    picture := opencv.ToImage(photo)
    println picture.width
    _ := opencv.FromImage(image.New(8, 8))
end

`ok`

func ok(): bool

Whether it is open.

The example for this item is shown with the ones above: opencv-Detect.salam

`read`

func read(): Mat

The next frame; empty at the end.

The example for this item is shown with the ones above: opencv-Detect.salam

`fps`

func fps(): f64

Frames per second.

The example for this item is shown with the ones above: opencv-Detect.salam

`frame_count`

func frame_count(): int

The number of frames.

The example for this item is shown with the ones above: opencv-Detect.salam

`close`

func close()

Closes it.

The example for this item is shown with the ones above: opencv-Detect.salam

`VideoWriter`

struct VideoWriter

Writes video.

Name	Type	Description
`handle`	`void*`	The internal handle.

The example for this item is shown with the ones above: opencv-Detect.salam

`ok`

func ok(): bool

Whether it is open.

The example for this item is shown with the ones above: opencv-Detect.salam

`write`

func write(frame: Mat): bool

Writes a frame.

The example for this item is shown with the ones above: opencv-Detect.salam

`close`

func close()

Closes it.

The example for this item is shown with the ones above: opencv-Detect.salam

`DetectedObject`

struct DetectedObject

A detected object.

Name	Type	Description
`x`	`int = 0`	x.
`y`	`int = 0`	y.
`width`	`int = 0`	The width.
`height`	`int = 0`	The height.

The example for this item is shown with the ones above: opencv-Detect.salam

`CascadeClassifier`

struct CascadeClassifier

A Haar cascade classifier; for face detection.

Name	Type	Description
`handle`	`void*`	The internal handle.

The example for this item is shown with the ones above: opencv-Detect.salam

`ok`

func ok(): bool

Whether it loaded.

The example for this item is shown with the ones above: opencv-Detect.salam

`detect`

func detect(m: Mat, scale_factor: f64, min_neighbors: int, max_results: int): Vector<DetectedObject>

Finds objects with a scale factor and a minimum neighbor count.

The example for this item is shown with the ones above: opencv-Detect.salam

`free`

func free()

Frees it.

The example for this item is shown with the ones above: opencv-Detect.salam

`Contours`

struct Contours

Contours.

Name	Type	Description
`handle`	`void*`	The internal handle.

opencv-Features.salam

import opencv

func main:
    mut scene := opencv.Read("scene_en.jpg")
    mut target := opencv.Read("object_en.jpg")
    mut contours := scene.to_gray().threshold_otsu(255.0).find_contours()
    println contours.ok(), contours.count()
    repeat contours.count() in i:
        box := contours.bounding_rect(i)
        println contours.area(i), contours.point_count(i), contours.point(i, 0).x, box.x, box.y, box.width, box.height
        scene.draw_contour(contours, i, opencv.Green(), 2)
    end
    contours.free()

    corners := scene.to_gray().good_features(50, 0.01, 10.0)
    println corners.len()
    mut keys1 := scene.detect_orb(500)
    mut keys2 := target.detect_orb(500)
    mut sift := scene.detect_sift(500)
    println keys1.ok(), keys1.count(), sift.count()
    if keys1.count() > 0:
        first := keys1.get(0)
        println first.x, first.y, first.size, first.angle, first.response
    end
    matches := opencv.MatchDescriptors(keys1.descriptors(), keys2.descriptors(), 50, opencv.NORM_HAMMING)
    each m in matches:
        println m.query_idx, m.train_idx, m.distance
    end
    println opencv.NORM_L2
    keys1.free()
    keys2.free()
    sift.free()

    found := scene.find_template(target)
    println found.found, found.x, found.y, found.score
    mut quad := Vector {} as Vector<opencv.Point>
    quad.push(opencv.Point { x = 0, y = 0 })
    quad.push(opencv.Point { x = 400, y = 10 })
    quad.push(opencv.Point { x = 410, y = 580 })
    quad.push(opencv.Point { x = 5, y = 590 })
    flat := scene.warp_perspective(quad, 420, 594)
    _ := opencv.Write("document_en.png", flat)
end

`ok`

func ok(): bool

Whether it is valid.

The example for this item is shown with the ones above: opencv-Features.salam

`count`

func count(): int

The number of contours.

The example for this item is shown with the ones above: opencv-Features.salam

`point_count`

func point_count(idx: int): int

The number of points in a contour.

The example for this item is shown with the ones above: opencv-Features.salam

`point`

func point(idx: int, pt_idx: int): Point

One point.

The example for this item is shown with the ones above: opencv-Features.salam

`area`

func area(idx: int): f64

The area.

The example for this item is shown with the ones above: opencv-Features.salam

`bounding_rect`

func bounding_rect(idx: int): Rect

The bounding rectangle.

The example for this item is shown with the ones above: opencv-Features.salam

`free`

func free()

Frees it.

The example for this item is shown with the ones above: opencv-Features.salam

`Keypoint`

struct Keypoint

One keypoint.

Name	Type	Description
`x`	`f64 = 0`	x.
`y`	`f64 = 0`	y.
`size`	`f64 = 0`	The size.
`angle`	`f64 = 0`	The angle.
`response`	`f64 = 0`	The strength.

The example for this item is shown with the ones above: opencv-Features.salam

`Keypoints`

struct Keypoints

Keypoints and descriptors.

Name	Type	Description
`handle`	`void*`	The internal handle.

The example for this item is shown with the ones above: opencv-Features.salam

`ok`

func ok(): bool

Whether it is valid.

The example for this item is shown with the ones above: opencv-Features.salam

`count`

func count(): int

The count.

The example for this item is shown with the ones above: opencv-Features.salam

`get`

func get(i: int): Keypoint

Keypoint i.

The example for this item is shown with the ones above: opencv-Features.salam

`descriptors`

func descriptors(): Mat

The descriptors.

The example for this item is shown with the ones above: opencv-Features.salam

`free`

func free()

Frees it.

The example for this item is shown with the ones above: opencv-Features.salam

`Match`

struct Match

One match.

Name	Type	Description
`query_idx`	`int = 0`	The index in the first set.
`train_idx`	`int = 0`	The index in the second set.
`distance`	`f64 = 0`	The distance; lower means more alike.

The example for this item is shown with the ones above: opencv-Features.salam

`Net`

struct Net

A DNN neural network.

Name	Type	Description
`handle`	`void*`	The internal handle.

The example for this item is shown with the ones above: opencv-Detect.salam

`ok`

func ok(): bool

Whether it loaded.

The example for this item is shown with the ones above: opencv-Detect.salam

`set_input`

func set_input(image: Mat, scale: f64, mean: Color, swap_rb: bool, size: Size): bool

Prepares the input with a scale, a mean, a channel swap and a size.

The example for this item is shown with the ones above: opencv-Detect.salam

`forward`

func forward(): Mat

Runs the network.

The example for this item is shown with the ones above: opencv-Detect.salam

`forward_layer`

func forward_layer(layer_name: str): Mat

The output of one layer.

The example for this item is shown with the ones above: opencv-Detect.salam

`free`

func free()

Frees it.

The example for this item is shown with the ones above: opencv-Detect.salam

`Detection`

struct Detection

One object found with DNN.

Name	Type	Description
`class_id`	`int = 0`	The class number.
`confidence`	`f64 = 0`	The confidence.
`x`	`int = 0`	x.
`y`	`int = 0`	y.
`width`	`int = 0`	The width.
`height`	`int = 0`	The height.

The example for this item is shown with the ones above: opencv-Features.salam

`Mat`

struct Mat

An OpenCV image or matrix with BGR channels.

Name	Type	Description
`handle`	`void*`	The internal handle.

opencv-Basics.salam

import opencv

func main:
    if not opencv.Available():
        println "OpenCV is not available:", opencv.LastError()
        ret
    end
    println opencv.Version()
    mut photo := opencv.Read("photo_en.jpg")
    if not photo.ok() or photo.empty():
        photo = opencv.NewBlank(320, 240, 3, opencv.White())
    end
    dims := photo.size()
    println photo.width(), photo.height(), photo.channels(), dims.width, dims.height, photo.step(), photo.total(), photo.data() != null
    color := photo.at(10, 10)
    println color.r, color.g, color.b
    photo.set_pixel(0, 0, opencv.RGB(255, 128, 0))
    black := opencv.Zeros(10, 10, 1)
    println black.channels(), opencv.Black().r, opencv.Red().r, opencv.Green().g, opencv.Blue().b

    gray := photo.to_gray()
    _ := photo.to_rgb()
    hsv := photo.to_hsv()
    _ := hsv.hsv_to_rgb()
    _ := photo.convert_color(opencv.COLOR_BGR2GRAY)
    _ := gray.convert_color(opencv.COLOR_GRAY2BGR)
    println opencv.COLOR_RGB2GRAY, opencv.COLOR_GRAY2RGB, opencv.COLOR_BGR2RGB, opencv.COLOR_RGB2BGR, opencv.COLOR_BGR2HSV, opencv.COLOR_HSV2BGR, opencv.COLOR_RGB2HSV, opencv.COLOR_HSV2RGB

    small := photo.resize(160, 120, opencv.INTERP_AREA)
    _ := photo.resize_scale(2.0, 2.0)
    _ := photo.crop(10, 10, 100, 80)
    _ := photo.rotate90(opencv.ROTATE_90_CW)
    _ := photo.rotate(45.0, 1.0)
    _ := photo.flip(opencv.FLIP_BOTH)
    _ := photo.flip_horizontal()
    _ := photo.flip_vertical()
    println opencv.INTERP_NEAREST, opencv.INTERP_LINEAR, opencv.INTERP_CUBIC, opencv.INTERP_LANCZOS4, opencv.ROTATE_180, opencv.ROTATE_90_CCW, opencv.FLIP_VERTICAL, opencv.FLIP_HORIZONTAL
    copied := small.clone()
    println copied.save("small_en.png"), opencv.Write("gray_en.png", gray)
    copied.free()
    photo.free()
end

`ok`

func ok(): bool

Whether it is valid.

The example for this item is shown with the ones above: opencv-Basics.salam

`empty`

func empty(): bool

Whether it is empty.

The example for this item is shown with the ones above: opencv-Basics.salam

`width`

func width(): int

The width.

The example for this item is shown with the ones above: opencv-Basics.salam

`height`

func height(): int

The height.

The example for this item is shown with the ones above: opencv-Basics.salam

`channels`

func channels(): int

The number of channels.

The example for this item is shown with the ones above: opencv-Basics.salam

`size`

func size(): Size

The size.

The example for this item is shown with the ones above: opencv-Features.salam

`clone`

func clone(): Mat

A copy.

The example for this item is shown with the ones above: opencv-Basics.salam

`free`

func free()

Frees it.

The example for this item is shown with the ones above: opencv-Basics.salam

`save`

func save(path: str): bool

Saves it to a file.

The example for this item is shown with the ones above: opencv-Basics.salam

`data`

func data(): void*

A pointer to the pixels.

The example for this item is shown with the ones above: opencv-Basics.salam

`step`

func step(): int

The bytes in each row.

The example for this item is shown with the ones above: opencv-Basics.salam

`total`

func total(): int

The number of pixels.

The example for this item is shown with the ones above: opencv-Basics.salam

`at`

func at(x: int, y: int): Color

The color of a pixel.

The example for this item is shown with the ones above: opencv-Basics.salam

`set_pixel`

func set_pixel(x: int, y: int, c: Color)

Sets the color of a pixel.

The example for this item is shown with the ones above: opencv-Basics.salam

`convert_color`

func convert_color(code: int): Mat

Converts the colors with one of the conversion constants.

The example for this item is shown with the ones above: opencv-Basics.salam

`to_gray`

func to_gray(): Mat

Gray.

The example for this item is shown with the ones above: opencv-Basics.salam

`to_rgb`

func to_rgb(): Mat

RGB.

The example for this item is shown with the ones above: opencv-Basics.salam

`to_hsv`

func to_hsv(): Mat

HSV; for picking out a color.

The example for this item is shown with the ones above: opencv-Basics.salam

`hsv_to_rgb`

func hsv_to_rgb(): Mat

HSV to RGB.

The example for this item is shown with the ones above: opencv-Basics.salam

`resize`

func resize(width: int, height: int, interpolation: int): Mat

Resizes with an interpolation method.

The example for this item is shown with the ones above: opencv-Basics.salam

`resize_scale`

func resize_scale(fx: f64, fy: f64): Mat

Resizes by a factor.

The example for this item is shown with the ones above: opencv-Basics.salam

`crop`

func crop(x: int, y: int, w: int, h: int): Mat

Cuts out a rectangle.

The example for this item is shown with the ones above: opencv-Basics.salam

`rotate90`

func rotate90(code: int): Mat

Rotates by a multiple of ninety degrees.

The example for this item is shown with the ones above: opencv-Basics.salam

`rotate`

func rotate(angle_degrees: f64, scale: f64): Mat

Rotates by an angle and a scale.

The example for this item is shown with the ones above: opencv-Basics.salam

`flip`

func flip(mode: int): Mat

Flips.

The example for this item is shown with the ones above: opencv-Basics.salam

`flip_horizontal`

func flip_horizontal(): Mat

Flips horizontally.

The example for this item is shown with the ones above: opencv-Basics.salam

`flip_vertical`

func flip_vertical(): Mat

Flips vertically.

The example for this item is shown with the ones above: opencv-Basics.salam

`blur`

func blur(ksize: int): Mat

Mean blur.

The example for this item is shown with the ones above: opencv-Basics.salam

`gaussian_blur`

func gaussian_blur(ksize: int, sigma: f64): Mat

Gaussian blur.

The example for this item is shown with the ones above: opencv-Basics.salam

`median_blur`

func median_blur(ksize: int): Mat

Median blur; for salt and pepper noise.

The example for this item is shown with the ones above: opencv-Basics.salam

`canny`

func canny(t1: f64, t2: f64): Mat

Canny edge detection with two thresholds.

The example for this item is shown with the ones above: opencv-Basics.salam

`threshold`

func threshold(thresh: f64, maxval: f64, kind: int): Mat

Applies a threshold.

The example for this item is shown with the ones above: opencv-Basics.salam

`threshold_otsu`

func threshold_otsu(maxval: f64): Mat

Otsu's automatic threshold.

The example for this item is shown with the ones above: opencv-Basics.salam

`adaptive_threshold`

func adaptive_threshold(maxval: f64, method: int, kind: int, block_size: int, c: f64): Mat

Adaptive threshold; for uneven light.

The example for this item is shown with the ones above: opencv-Basics.salam

`histogram_gray`

func histogram_gray(): Vector<int>

The 256 bin histogram of a gray image.

The example for this item is shown with the ones above: opencv-Basics.salam

`line`

func line(x1: int, y1: int, x2: int, y2: int, color: Color, thickness: int)

A line.

The example for this item is shown with the ones above: opencv-Basics.salam

`rectangle`

func rectangle(x: int, y: int, w: int, h: int, color: Color, thickness: int)

A rectangle; a negative thickness fills it.

The example for this item is shown with the ones above: opencv-Basics.salam

`circle`

func circle(cx: int, cy: int, radius: int, color: Color, thickness: int)

A circle.

The example for this item is shown with the ones above: opencv-Basics.salam

`put_text`

func put_text(text: str, x: int, y: int, font_scale: f64, color: Color, thickness: int)

Latin text.

The example for this item is shown with the ones above: opencv-Basics.salam

`good_features`

func good_features(max_corners: int, quality: f64, min_dist: f64): Vector<Point>

Good corners to track.

The example for this item is shown with the ones above: opencv-Basics.salam

`detect_orb`

func detect_orb(max_features: int): Keypoints

ORB keypoints and descriptors.

The example for this item is shown with the ones above: opencv-Basics.salam

`detect_sift`

func detect_sift(max_features: int): Keypoints

SIFT keypoints.

The example for this item is shown with the ones above: opencv-Basics.salam

`erode`

func erode(ksize: int, iterations: int): Mat

Erosion.

The example for this item is shown with the ones above: opencv-Basics.salam

`dilate`

func dilate(ksize: int, iterations: int): Mat

Dilation.

The example for this item is shown with the ones above: opencv-Basics.salam

`morphology`

func morphology(op: int, ksize: int): Mat

A morphological operation.

The example for this item is shown with the ones above: opencv-Basics.salam

`blend`

func blend(other: Mat, alpha: f64, beta: f64, gamma: f64): Mat

A weighted blend of two images.

The example for this item is shown with the ones above: opencv-Basics.salam

`bitwise`

func bitwise(other: Mat, op: int): Mat

A bitwise operation with another image.

The example for this item is shown with the ones above: opencv-Basics.salam

`bitwise_not`

func bitwise_not(): Mat

Bitwise NOT.

The example for this item is shown with the ones above: opencv-Basics.salam

`abs_diff`

func abs_diff(other: Mat): Mat

The absolute difference; for motion detection.

The example for this item is shown with the ones above: opencv-Basics.salam

`warp_perspective`

func warp_perspective(src: Vector<Point>, out_width: int, out_height: int): Mat

Turns four corners into a flat rectangle; for scanning documents.

The example for this item is shown with the ones above: opencv-Basics.salam

`find_template`

func find_template(template: Mat): TemplateMatch

Where a template sits in the image.

The example for this item is shown with the ones above: opencv-Basics.salam

`ellipse`

func ellipse(cx: int, cy: int, axis_width: int, axis_height: int, angle_degrees: f64, color: Color, thickness: int)

An ellipse.

The example for this item is shown with the ones above: opencv-Basics.salam

`polylines`

func polylines(pts: Vector<Point>, closed: bool, color: Color, thickness: int)

A polyline.

The example for this item is shown with the ones above: opencv-Basics.salam

`fill_poly`

func fill_poly(pts: Vector<Point>, color: Color)

A filled polygon.

The example for this item is shown with the ones above: opencv-Basics.salam

`find_contours`

func find_contours(): Contours

The contours of the shapes in a binary image.

The example for this item is shown with the ones above: opencv-Basics.salam

`draw_contour`

func draw_contour(cs: Contours, idx: int, color: Color, thickness: int)

Draws one contour.

The example for this item is shown with the ones above: opencv-Basics.salam

`TemplateMatch`

struct TemplateMatch

The result of a template search.

Name	Type	Description
`found`	`bool = false`	Whether it was found.
`x`	`int = 0`	x.
`y`	`int = 0`	y.
`score`	`f64 = 0`	The match score.

The example for this item is shown with the ones above: opencv-Features.salam

`Size`

struct Size

A size.

Name	Type	Description
`width`	`int = 0`	The width.
`height`	`int = 0`	The height.

The example for this item is shown with the ones above: opencv-Basics.salam

`Point`

struct Point

A point.

Name	Type	Description
`x`	`int = 0`	x.
`y`	`int = 0`	y.

opencv-Filters.salam

import opencv

func main:
    mut photo := opencv.Read("photo_en.jpg")
    gray := photo.to_gray()
    _ := photo.blur(5)
    _ := photo.gaussian_blur(5, 1.5)
    _ := photo.median_blur(5)
    edges := gray.canny(50.0, 150.0)
    _ := gray.threshold(128.0, 255.0, opencv.THRESH_BINARY)
    _ := gray.threshold_otsu(255.0)
    _ := gray.adaptive_threshold(255.0, opencv.ADAPTIVE_GAUSSIAN, opencv.THRESH_BINARY, 11, 2.0)
    println opencv.THRESH_BINARY_INV, opencv.THRESH_TRUNC, opencv.THRESH_TOZERO, opencv.THRESH_TOZERO_INV, opencv.THRESH_OTSU, opencv.ADAPTIVE_MEAN
    println gray.histogram_gray().len()
    _ := edges.erode(3, 1)
    _ := edges.dilate(3, 2)
    _ := edges.morphology(opencv.MORPH_CLOSE, 5)
    println opencv.MORPH_OPEN, opencv.MORPH_GRADIENT, opencv.MORPH_TOPHAT, opencv.MORPH_BLACKHAT
    white := opencv.NewBlank(photo.width(), photo.height(), 3, opencv.White())
    _ := photo.blend(white, 0.7, 0.3, 0.0)
    _ := photo.bitwise(white, opencv.BITWISE_AND)
    _ := photo.bitwise(white, opencv.BITWISE_OR)
    _ := photo.bitwise(white, opencv.BITWISE_XOR)
    _ := photo.bitwise_not()
    _ := photo.abs_diff(white)
    photo.line(0, 0, 100, 100, opencv.Red(), 2)
    photo.rectangle(10, 10, 50, 30, opencv.Green(), 1)
    photo.circle(80, 80, 20, opencv.Blue(), -1)
    photo.ellipse(100, 50, 40, 20, 30.0, opencv.Black(), 2)
    photo.put_text("Salam", 10, 200, 1.0, opencv.White(), 2)
    mut points := Vector {} as Vector<opencv.Point>
    points.push(opencv.Point { x = 0, y = 0 })
    points.push(opencv.Point { x = 50, y = 0 })
    points.push(opencv.Point { x = 25, y = 40 })
    photo.polylines(points, true, opencv.Red(), 2)
    photo.fill_poly(points, opencv.Green())
    _ := opencv.Write("filtered_en.png", photo)
end

`Rect`

struct Rect

A rectangle.

Name	Type	Description
`x`	`int = 0`	x.
`y`	`int = 0`	y.
`width`	`int = 0`	The width.
`height`	`int = 0`	The height.

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`Color`

struct Color

A color.

Name	Type	Description
`r`	`int = 0`	Red.
`g`	`int = 0`	Green.
`b`	`int = 0`	Blue.

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Constants and variables

`COLOR_BGR2GRAY`

const COLOR_BGR2GRAY: i32 = 0

Color conversion: BGR to gray.

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`COLOR_GRAY2BGR`

const COLOR_GRAY2BGR: i32 = 1

Color conversion: gray to BGR.

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`COLOR_RGB2GRAY`

const COLOR_RGB2GRAY: i32 = 2

Color conversion: RGB to gray.

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`COLOR_GRAY2RGB`

const COLOR_GRAY2RGB: i32 = 3

Color conversion: gray to RGB.

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`COLOR_BGR2RGB`

const COLOR_BGR2RGB: i32 = 4

Color conversion: BGR to RGB.

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`COLOR_RGB2BGR`

const COLOR_RGB2BGR: i32 = 5

Color conversion: RGB to BGR.

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`COLOR_BGR2HSV`

const COLOR_BGR2HSV: i32 = 6

Color conversion: BGR to HSV.

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`COLOR_HSV2BGR`

const COLOR_HSV2BGR: i32 = 7

Color conversion: HSV to BGR.

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`COLOR_RGB2HSV`

const COLOR_RGB2HSV: i32 = 8

Color conversion: RGB to HSV.

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`COLOR_HSV2RGB`

const COLOR_HSV2RGB: i32 = 9

Color conversion: HSV to RGB.

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`THRESH_BINARY`

const THRESH_BINARY: i32 = 0

Threshold: the maximum above the threshold, zero elsewhere.

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`THRESH_BINARY_INV`

const THRESH_BINARY_INV: i32 = 1

Threshold: inverted binary.

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`THRESH_TRUNC`

const THRESH_TRUNC: i32 = 2

Threshold: values above the threshold become the threshold.

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`THRESH_TOZERO`

const THRESH_TOZERO: i32 = 3

Threshold: values below the threshold become zero.

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`THRESH_TOZERO_INV`

const THRESH_TOZERO_INV: i32 = 4

Threshold: values above the threshold become zero.

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`THRESH_OTSU`

const THRESH_OTSU: i32 = 5

Threshold: Otsu's automatic threshold.

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`ADAPTIVE_MEAN`

const ADAPTIVE_MEAN: i32 = 0

Adaptive threshold with the neighborhood mean.

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`ADAPTIVE_GAUSSIAN`

const ADAPTIVE_GAUSSIAN: i32 = 1

Adaptive threshold with a Gaussian weighted mean.

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`INTERP_NEAREST`

const INTERP_NEAREST: i32 = 0

Interpolation: nearest neighbor.

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`INTERP_LINEAR`

const INTERP_LINEAR: i32 = 1

Interpolation: bilinear.

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`INTERP_CUBIC`

const INTERP_CUBIC: i32 = 2

Interpolation: bicubic.

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`INTERP_AREA`

const INTERP_AREA: i32 = 3

Interpolation: area based, the best for shrinking.

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`INTERP_LANCZOS4`

const INTERP_LANCZOS4: i32 = 4

Interpolation: Lanczos.

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`ROTATE_90_CW`

const ROTATE_90_CW: i32 = 0

Rotate ninety degrees clockwise.

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`ROTATE_180`

const ROTATE_180: i32 = 1

Rotate one hundred and eighty degrees.

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`ROTATE_90_CCW`

const ROTATE_90_CCW: i32 = 2

Rotate ninety degrees counterclockwise.

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`FLIP_VERTICAL`

const FLIP_VERTICAL: i32 = 0

Vertical flip.

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`FLIP_HORIZONTAL`

const FLIP_HORIZONTAL: i32 = 1

Horizontal flip.

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`FLIP_BOTH`

const FLIP_BOTH: i32 = 2

Flip in both directions.

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`MORPH_OPEN`

const MORPH_OPEN: i32 = 0

Opening: erosion then dilation; removes small specks.

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`MORPH_CLOSE`

const MORPH_CLOSE: i32 = 1

Closing: dilation then erosion; fills small holes.

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`MORPH_GRADIENT`

const MORPH_GRADIENT: i32 = 2

Gradient: the outline of the shapes.

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`MORPH_TOPHAT`

const MORPH_TOPHAT: i32 = 3

Top hat.

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`MORPH_BLACKHAT`

const MORPH_BLACKHAT: i32 = 4

Black hat.

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`BITWISE_AND`

const BITWISE_AND: i32 = 0

Bitwise AND.

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`BITWISE_OR`

const BITWISE_OR: i32 = 1

Bitwise OR.

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`BITWISE_XOR`

const BITWISE_XOR: i32 = 2

Bitwise exclusive or.

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`NORM_HAMMING`

const NORM_HAMMING: i32 = 0

Hamming distance; for ORB descriptors.

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`NORM_L2`

const NORM_L2: i32 = 1

Euclidean distance; for SIFT.

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Functions

`OpenVideo`

func OpenVideo(path: str): VideoCapture

Opens a video file.

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`OpenCamera`

func OpenCamera(index: int): VideoCapture

A camera by number.

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`NewVideoWriter`

func NewVideoWriter(path: str, fourcc: str, fps: f64, width: int, height: int): VideoWriter

A writer with a four letter codec, frames per second and a size.

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`LoadCascade`

func LoadCascade(path: str): CascadeClassifier

Loads a classifier from an XML file.

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`MatchDescriptors`

func MatchDescriptors(desc1: Mat, desc2: Mat, max_matches: int, norm: int): Vector<Match>

The best matches between two sets of descriptors.

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`LoadNet`

func LoadNet(model_path: str, config_path: str): Net

A model and its configuration, such as Caffe.

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`LoadNetSingleFile`

func LoadNetSingleFile(path: str): Net

A single file model, such as ONNX.

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`ParseSSDDetections`

func ParseSSDDetections(output: Mat, img_width: int, img_height: int, confidence_threshold: f64): Vector<Detection>

Turns SSD output into the objects whose confidence is above the threshold.

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`Imshow`

func Imshow(window: str, m: Mat)

Shows an image in a window.

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`WaitKey`

func WaitKey(delay_ms: int): int

Waits up to delay milliseconds for a key; the key code or -1.

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`DestroyWindow`

func DestroyWindow(window: str)

Closes a window.

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`DestroyAllWindows`

func DestroyAllWindows()

Closes all windows.

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`CreateTrackbar`

func CreateTrackbar(name: str, window: str, initial: int, max: int): bool

A slider in a window.

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`GetTrackbarPos`

func GetTrackbarPos(name: str, window: str): int

The position of a slider.

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`SetTrackbarPos`

func SetTrackbarPos(name: str, window: str, pos: int)

Sets the position.

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`LastError`

func LastError(): str

The message of the last error.

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`Available`

func Available(): bool

Whether the OpenCV library is loaded.

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`Version`

func Version(): str

The OpenCV version.

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`RGB`

func RGB(r: int, g: int, b: int): Color

A color from red, green and blue.

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`Black`

func Black(): Color

Black.

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`White`

func White(): Color

White.

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`Red`

func Red(): Color

Red.

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`Green`

func Green(): Color

Green.

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`Blue`

func Blue(): Color

Blue.

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`Read`

func Read(path: str): Mat

Reads an image from a file.

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`Write`

func Write(path: str, m: Mat): bool

Writes an image to a file.

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`NewBlank`

func NewBlank(width: int, height: int, channels: int, fill: Color): Mat

A canvas filled with a color.

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`Zeros`

func Zeros(width: int, height: int, channels: int): Mat

A black canvas.

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`FromImage`

func FromImage(img: image.Image): Mat

From an image of the image package.

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`ToImage`

func ToImage(m: Mat): image.Image

To an image of the image package.

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