swift 获取当前帧的rgb值

在Swift中，要获取当前帧的RGB值，可以使用AVFoundation框架中的AVCaptureVideoDataOutput类。以下是一个简单的示例代码：

import AVFoundation

// 创建一个AVCaptureSession对象
let captureSession = AVCaptureSession()

// 创建一个AVCaptureDevice对象，例如前置摄像头
let captureDevice = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .front)

// 创建一个AVCaptureDeviceInput对象
let captureDeviceInput = try? AVCaptureDeviceInput(device: captureDevice!)

// 将AVCaptureDeviceInput对象添加到AVCaptureSession对象中
if captureSession.canAddInput(captureDeviceInput!) {
    captureSession.addInput(captureDeviceInput!)
}

// 创建一个AVCaptureVideoDataOutput对象，并设置输出格式为32位RGB
let captureVideoDataOutput = AVCaptureVideoDataOutput()
captureVideoDataOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_32BGRA)]

// 将AVCaptureVideoDataOutput对象添加到AVCaptureSession对象中
if captureSession.canAddOutput(captureVideoDataOutput) {
    captureSession.addOutput(captureVideoDataOutput)
}

// 开始捕获视频帧
captureSession.startRunning()

// 获取当前帧的RGB值
captureVideoDataOutput.setSampleBufferDelegate(self, queue: DispatchQueue(label: "sample buffer delegate queue"))

extension ViewController: AVCaptureVideoDataOutputSampleBufferDelegate {
    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else {
            return
        }
        
        CVPixelBufferLockBaseAddress(pixelBuffer, .readOnly)
        
        let width = CVPixelBufferGetWidth(pixelBuffer)
        let height = CVPixelBufferGetHeight(pixelBuffer)
        let bytesPerRow = CVPixelBufferGetBytesPerRow(pixelBuffer)
        let baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer)
        
        // 计算当前帧的RGB值
        let bytes = baseAddress!.assumingMemoryBound(to: UInt8.self)
        let pixel = (height / 2) * bytesPerRow + (width / 2) * 4
        let r = bytes[pixel + 2]
        let g = bytes[pixel + 1]
        let b = bytes[pixel]
        
        CVPixelBufferUnlockBaseAddress(pixelBuffer, .readOnly)
        
        print("当前帧的RGB值为：\(r), \(g), \(b)")
    }
}

需要注意的是，获取RGB值需要摄像头支持，并且需要用户授权。同时，由于视频帧数据是实时获取的，因此需要在适当的时候停止获取，以避免对设备性能产生不必要的影响。