即时将图像添加到 AR 资源以进行图像识别

Question

ARKit 1.5 引入了图像识别。在代码中，您必须像这样创建一组参考图像：

let referenceImages = ARReferenceImage.referenceImages(inGroupNamed: "AR Resources", bundle: nil)

然后可以识别集合中包含的图像。

我想知道是否可以将图像即时添加到此AR Resources 文件夹。例如，用户可以拍照并将其发送到服务器，然后由ARKit 识别。或者用户可以根据他的位置等接收一组图像。

Answer 1

您不能在运行时修改默认文件夹的内容，但您可以即时创建图像。

例如，让我们将图像放入Assets Folder（不是 ARResources 中），在我的例子中称为“moonTarget”。

然后我们可以创建一个在viewDidLoad 等中调用的函数：

/// Create ARReference Images From Somewhere Other Than The Default Folder
func loadDynamicImageReferences(){

    //1. Get The Image From The Folder
    guard let imageFromBundle = UIImage(named: "moonTarget"),
    //2. Convert It To A CIImage
    let imageToCIImage = CIImage(image: imageFromBundle),
    //3. Then Convert The CIImage To A CGImage
    let cgImage = convertCIImageToCGImage(inputImage: imageToCIImage)else { return }

    //4. Create An ARReference Image (Remembering Physical Width Is In Metres)
    let arImage = ARReferenceImage(cgImage, orientation: CGImagePropertyOrientation.up, physicalWidth: 0.2)

    //5. Name The Image
    arImage.name = "CGImage Test"

    //5. Set The ARWorldTrackingConfiguration Detection Images
    configuration.detectionImages = [arImage]
}


/// Converts A CIImage To A CGImage
///
/// - Parameter inputImage: CIImage
/// - Returns: CGImage
func convertCIImageToCGImage(inputImage: CIImage) -> CGImage? {
    let context = CIContext(options: nil)
    if let cgImage = context.createCGImage(inputImage, from: inputImage.extent) {
     return cgImage
    }
    return nil
}

然后我们可以在ARSCNViewDelegate 中进行测试：

func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {

    //1. If Out Target Image Has Been Detected Than Get The Corresponding Anchor
    guard let currentImageAnchor = anchor as? ARImageAnchor else { return }

    let x = currentImageAnchor.transform
    print(x.columns.3.x, x.columns.3.y , x.columns.3.z)

    //2. Get The Targets Name
    let name = currentImageAnchor.referenceImage.name!

    //3. Get The Targets Width & Height In Meters
    let width = currentImageAnchor.referenceImage.physicalSize.width
    let height = currentImageAnchor.referenceImage.physicalSize.height

    print("""
    Image Name = \(name)
    Image Width = \(width)
    Image Height = \(height)
    """)

    //4. Create A Plane Geometry To Cover The ARImageAnchor
    let planeNode = SCNNode()
    let planeGeometry = SCNPlane(width: width, height: height)
    planeGeometry.firstMaterial?.diffuse.contents = UIColor.white
    planeNode.opacity = 0.25
    planeNode.geometry = planeGeometry

    //5. Rotate The PlaneNode To Horizontal
    planeNode.eulerAngles.x = -.pi/2

    //The Node Is Centered In The Anchor (0,0,0)
    node.addChildNode(planeNode)

    //6. Create AN SCNBox
    let boxNode = SCNNode()
    let boxGeometry = SCNBox(width: 0.1, height: 0.1, length: 0.1, chamferRadius: 0)

    //7. Create A Different Colour For Each Face
    let faceColours = [UIColor.red, UIColor.green, UIColor.blue, UIColor.cyan, UIColor.yellow, UIColor.gray]
    var faceMaterials = [SCNMaterial]()

    //8. Apply It To Each Face
    for face in 0 ..< 5{
        let material = SCNMaterial()
        material.diffuse.contents = faceColours[face]
        faceMaterials.append(material)
    }
    boxGeometry.materials = faceMaterials
    boxNode.geometry = boxGeometry

    //9. Set The Boxes Position To Be Placed On The Plane (node.x + box.height)
    boxNode.position = SCNVector3(0 , 0.05, 0)

    //10. Add The Box To The Node
    node.addChildNode(boxNode)   
}

如您所见，也可以从实时提要中应用相同的内容。

希望这会有所帮助...

正如@Karlis 所说，您也可以考虑使用OnDemandResouces，然后将它们转换为ARReferenceImage 的所需规格。

更新：对于希望查看从服务器创建动态参考图像的示例的任何人，请查看我创建的以下项目：Dynamic Reference Images Sample Code

Answer 2

let documentDirectory = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
let pathToObject = documentDirectory + "/reference.jpg"
let imageUrl = URL(fileURLWithPath: pathToObject)
let imageData: Data = try! Data(contentsOf: imageUrl)
let image = UIImage(data: imageData, scale: UIScreen.main.scale)
let cgImage = image!.cgImage

let referenceImages = ARReferenceImage.init(cgImage!, orientation: .up, physicalWidth: 0.595)
referenceImages.name = "Reference Image"
let configuration = ARImageTrackingConfiguration()
configuration.trackingImages = [referenceImages]
session.run(configuration, options: [.resetTracking, .removeExistingAnchors])