显然,我们可以使用 CoreImage 将图像转换为灰度、去噪和模糊,但当涉及到 Canny 边缘检测、轮廓检测和绘制形状轮廓时,似乎仅使用 swift 特征是不可能的。我是对的还是我在这里遗漏了什么?
现在您可以使用
VNDetectContoursRequest
使用适用于 iOS 14 的 SwiftUI 进行检测:
func detectVisionContours(){
let context = CIContext()
if let sourceImage = UIImage.init(named: "coin")
{
var inputImage = CIImage.init(cgImage: sourceImage.cgImage!)
let contourRequest = VNDetectContoursRequest.init()
contourRequest.revision = VNDetectContourRequestRevision1
contourRequest.contrastAdjustment = 1.0
contourRequest.detectDarkOnLight = true
contourRequest.maximumImageDimension = 512
let requestHandler = VNImageRequestHandler.init(ciImage: inputImage, options: [:])
try! requestHandler.perform([contourRequest])
let contoursObservation = contourRequest.results?.first as! VNContoursObservation
self.points = String(contoursObservation.contourCount)
self.contouredImage = drawContours(contoursObservation: contoursObservation, sourceImage: sourceImage.cgImage!)
} else {
self.points = "Could not load image"
}
}
要绘制轮廓,请执行以下操作:
public func drawContours(contoursObservation: VNContoursObservation, sourceImage: CGImage) -> UIImage {
let size = CGSize(width: sourceImage.width, height: sourceImage.height)
let renderer = UIGraphicsImageRenderer(size: size)
let renderedImage = renderer.image { (context) in
let renderingContext = context.cgContext
let flipVertical = CGAffineTransform(a: 1, b: 0, c: 0, d: -1, tx: 0, ty: size.height)
renderingContext.concatenate(flipVertical)
renderingContext.draw(sourceImage, in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
renderingContext.scaleBy(x: size.width, y: size.height)
renderingContext.setLineWidth(5.0 / CGFloat(size.width))
let redUIColor = UIColor.red
renderingContext.setStrokeColor(redUIColor.cgColor)
renderingContext.addPath(contoursObservation.normalizedPath)
renderingContext.strokePath()
}
return renderedImage
}
2020 年 6 月,Apple 在 iOS 14 的视觉框架中添加了新的轮廓检测功能。(目前处于测试阶段),因此您现在可以使用 Swift(不带 OpenCV)来检测轮廓。
您可以在 Apple 的此文档中找到更多详细信息:https://developer.apple.com/documentation/vision/vndetectcontoursrequest
同样相关的是这个 WWDC2020 视频:https://developer.apple.com/videos/play/wwdc2020/10673/