swift - Swiftui 获取图像的显示尺寸

Question

我正在尝试获取显示图像的尺寸，以便在我使用苹果的 Vision 框架识别的文本上绘制边界框。所以我在按下具有此功能的按钮时运行 VNRecognizeTextRequest

func readImage(image:NSImage, completionHandler:@escaping(([VNRecognizedText]?,Error?)->()), comp:@escaping((Double?,Error?)->())) {

var recognizedTexts = [VNRecognizedText]()
var rr = CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height)
let requestHandler = VNImageRequestHandler(cgImage: image.cgImage(forProposedRect: &rr, context: nil, hints: nil)!
, options: [:])
let textRequest = VNRecognizeTextRequest { (request, error) in
    guard let observations = request.results as? [VNRecognizedTextObservation] else { completionHandler(nil,error)
        return
    }
    for currentObservation in observations {
        let topCandidate = currentObservation.topCandidates(1)
        if let recognizedText = topCandidate.first {

            recognizedTexts.append(recognizedText)
        }
    }
    completionHandler(recognizedTexts,nil)
}

textRequest.recognitionLevel = .accurate
textRequest.recognitionLanguages = ["es"]
textRequest.usesLanguageCorrection = true

textRequest.progressHandler = {(request, value, error) in
    comp(value,nil)
}
try? requestHandler.perform([textRequest])

}

并使用此结构和函数计算边界框偏移量

struct DisplayingRect:Identifiable {

var id = UUID()
var width:CGFloat = 0
var height:CGFloat = 0
var xAxis:CGFloat = 0
var yAxis:CGFloat = 0

init(width:CGFloat, height:CGFloat, xAxis:CGFloat, yAxis:CGFloat) {
    self.width = width
    self.height = height
    self.xAxis = xAxis
    self.yAxis = yAxis
}

}

func createBoundingBoxOffSet(recognizedTexts:[VNRecognizedText], image:NSImage) -> [DisplayingRect] {
var rects = [DisplayingRect]()
let imageSize = image.size
let imageTransform = CGAffineTransform.identity.scaledBy(x: imageSize.width, y: imageSize.height)
for obs in recognizedTexts {
    let observationBounds = try? obs.boundingBox(for: obs.string.startIndex..<obs.string.endIndex)
    let rectangle = observationBounds?.boundingBox.applying(imageTransform)
    print("Rectange: \(rectangle!)")
    let width = rectangle!.width
    let height = rectangle!.height
    let xAxis = rectangle!.origin.x - imageSize.width / 2 + rectangle!.width / 2
    let yAxis = -(rectangle!.origin.y - imageSize.height / 2 + rectangle!.height / 2)
    let rect = DisplayingRect(width: width, height: height, xAxis: xAxis, yAxis: yAxis)
    rects.append(rect)
}

return(rects)

}

我在 ContentView 中使用此代码放置矩形

        ZStack{
            Image(nsImage: self.img!)
                .scaledToFit()
            ForEach(self.rects) { rect in
                Rectangle()
                    .fill(Color.init(.sRGB, red: 1, green: 0, blue: 0, opacity: 0.2))
                    .frame(width: rect.width, height: rect.height)
                    .offset(x: rect.xAxis, y: rect.yAxis)
            }
        }

如果我使用原件的图像尺寸，我会得到这些结果

但是如果我添加

                Image(nsImage: self.img!)
                  .resizable()
                  .scaledToFit()

我得到这些结果

有没有办法获取图像尺寸并传递它们并获得正在显示的图像的正确尺寸？我也需要这个，因为有时我无法显示整个图像并且需要缩放它。

非常感谢

标签： swiftxcodeswiftuiapple-vision

Answer 1

我会GeometryReader在背景上使用，因此它可以准确读取图像的大小，如下所示

@State var imageSize: CGSize = .zero // << or initial from NSImage
...
Image(nsImage: self.img!)
    .resizable()
    .scaledToFit()
    .background(rectReader())

// ... somewhere below 
private func rectReader() -> some View {
    return GeometryReader { (geometry) -> AnyView in
        let imageSize = geometry.size
        DispatchQueue.main.async {
            print(">> \(imageSize)") // use image actual size in your calculations
            self.imageSize = imageSize
        }
        return AnyView(Rectangle().fill(Color.clear))
    }
}