OpenCV-contrib-SPM

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

This swift package helps you easily import the prebuilt opencv2.xcframework into your project, so you no longer need to build it by yourself. It watches the release events in OpenCV Github Project with OpenCV_contrib and automatically creates new releases, using the powerful Github Actions.

Installation

1. Add https://github.com/xaviviro/opencv-contrib-spm.git to your package dependencies.

   

2. Add libc++ to your linked libraries, otherwise building will fail.

   

3. Add -all_load to Other Linker Flags, otherwise some methods cannot be used. opencv/opencv#17532

   

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()