OpenCV-SPM

Use OpenCV in your Swift project in a more elegant way.

This Swift package simplifies the process of importing the prebuilt opencv2.xcframework into your project, eliminating the need for manual building. It monitors release events in the OpenCV Github Project and automatically generates new releases using Github Actions.

Installation

Add https://github.com/gamechanger/opencv-spm.git to your package dependencies

Usage

Import opencv2 and use it as documented in opencv.org. For example, a swift version of Extract horizontal and vertical lines by using morphological operations:

import opencv2

// Show source image
let src = Mat(uiImage: image)

// Transform source image to gray if it is not already
let gray: Mat
if (src.channels() == 3) {
    gray = Mat()
    Imgproc.cvtColor(src: src, dst: gray, code: .COLOR_BGR2GRAY)
} else {
    gray = src
}

// Apply adaptiveThreshold at the bitwise_not of gray, notice the ~ symbol
let notGray = Mat()
Core.bitwise_not(src: gray, dst: notGray)

let bw = Mat()
Imgproc.adaptiveThreshold(src: notGray, dst: bw, maxValue: 255, adaptiveMethod: .ADAPTIVE_THRESH_MEAN_C, thresholdType: .THRESH_BINARY, blockSize: 15, C: -2)

// Create the images that will use to extract the horizontal lines
let horizontal = bw.clone()
let vertical = bw.clone()

// Specify size on horizontal axis
let horizontalSize = horizontal.cols() / 30
// Create structure element for extracting horizontal lines through morphology operations
let horizontalStructure = Imgproc.getStructuringElement(shape: .MORPH_RECT, ksize: .init(width: horizontalSize, height: 1))
// Apply morphology operations
Imgproc.erode(src: horizontal, dst: horizontal, kernel: horizontalStructure, anchor: .init(x: -1, y: -1))
Imgproc.dilate(src: horizontal, dst: horizontal, kernel: horizontalStructure, anchor: .init(x: -1, y: -1))

// Specify size on vertical axis
let verticalSize = vertical.rows() / 30

// Create structure element for extracting vertical lines through morphology operations
let verticalStructure = Imgproc.getStructuringElement(shape: .MORPH_RECT, ksize: .init(width: 1, height: verticalSize))

// Apply morphology operations
Imgproc.erode(src: vertical, dst: vertical, kernel: verticalStructure, anchor: .init(x: -1, y: -1))
Imgproc.dilate(src: vertical, dst: vertical, kernel: verticalStructure, anchor: .init(x: -1, y: -1))

// Inverse vertical image
Core.bitwise_not(src: vertical, dst: vertical)

// Extract edges and smooth image according to the logic
// 1. extract edges
// 2. dilate(edges)
// 3. src.copyTo(smooth)
// 4. blur smooth img
// 5. smooth.copyTo(src, edges)
// Step 1
let edges = Mat();
Imgproc.adaptiveThreshold(src: vertical, dst: edges, maxValue: 255, adaptiveMethod: .ADAPTIVE_THRESH_MEAN_C, thresholdType: .THRESH_BINARY, blockSize: 3, C: -2)

// Step 2
let kernel = Mat.ones(rows: 2, cols: 2, type: CvType.CV_8UC1)
Imgproc.dilate(src: edges, dst: edges, kernel: kernel)

// Step 3
let smooth = Mat();
vertical.copy(to: smooth)

// Step 4
Imgproc.blur(src: smooth, dst: smooth, ksize: .init(width: 2, height: 2))

// Step 5
smooth.copy(to: vertical, mask: edges)

// Show final result
let result = vertical.toUIImage()