如何将cvPixelBuffer裁剪为CGRect的边界？

要将cvPixelBuffer裁剪为CGRect的边界，您可以使用Core Graphics框架中的函数来执行此操作。以下是一个示例代码，该代码使用AVFoundation和Core Graphics来裁剪cvPixelBuffer。

import AVFoundation
import CoreGraphics
import CoreVideo

func cropPixelBuffer(_ pixelBuffer: CVPixelBuffer, toRect rect: CGRect) -> CVPixelBuffer? {
    let width = CVPixelBufferGetWidth(pixelBuffer)
    let height = CVPixelBufferGetHeight(pixelBuffer)
    
    var cropRect = rect
    cropRect.origin.x *= CGFloat(width)
    cropRect.origin.y *= CGFloat(height)
    cropRect.size.width *= CGFloat(width)
    cropRect.size.height *= CGFloat(height)
    
    var croppedPixelBuffer: CVPixelBuffer?
    
    CVPixelBufferCreate(nil, Int(cropRect.width), Int(cropRect.height), CVPixelBufferGetPixelFormatType(pixelBuffer), nil, &croppedPixelBuffer)
    
    guard let cropped = croppedPixelBuffer else {
        return nil
    }
    
    CVPixelBufferLockBaseAddress(pixelBuffer, .readOnly)
    CVPixelBufferLockBaseAddress(cropped, [])
    
    let srcBaseAddress = CVPixelBufferGetBaseAddress(pixelBuffer)
    let destBaseAddress = CVPixelBufferGetBaseAddress(cropped)
    
    CVPixelBufferFillExtendedPixels(cropped)
    
    let srcBytesPerRow = CVPixelBufferGetBytesPerRow(pixelBuffer)
    let destBytesPerRow = CVPixelBufferGetBytesPerRow(cropped)
    
    let srcStart = Int(cropRect.origin.y) * srcBytesPerRow + Int(cropRect.origin.x) * 4
    let destStart = 0
    
    let srcAddress = srcBaseAddress?.advanced(by: srcStart)
    let destAddress = destBaseAddress?.advanced(by: destStart)
    
    let srcBuffer = vImage_Buffer(data: srcAddress, height: vImagePixelCount(cropRect.height), width: vImagePixelCount(cropRect.width), rowBytes: srcBytesPerRow)
    let destBuffer = vImage_Buffer(data: destAddress, height: vImagePixelCount(cropRect.height), width: vImagePixelCount(cropRect.width), rowBytes: destBytesPerRow)
    
    vImageScale_ARGB8888(&srcBuffer, &destBuffer, nil, vImage_Flags(kvImageNoFlags))
    
    CVPixelBufferUnlockBaseAddress(pixelBuffer, .readOnly)
    CVPixelBufferUnlockBaseAddress(cropped, [])
    
    return cropped
}

这个函数接受一个cvPixelBuffer和一个CGRect作为参数，并返回裁剪后的cvPixelBuffer。请注意，此示例假定输入的cvPixelBuffer的像素格式为kCVPixelFormatType_32BGRA。如果您的像素格式不同，请相应地更改代码。

使用此函数，您可以将cvPixelBuffer裁剪为特定的CGRect边界。例如：

let pixelBuffer: CVPixelBuffer = // 获取输入的cvPixelBuffer
let cropRect = CGRect(x: 0.25, y: 0.25, width: 0.5, height: 0.5) // 定义要裁剪的边界

if let croppedPixelBuffer = cropPixelBuffer(pixelBuffer, toRect: cropRect) {
    // 使用裁剪后的cvPixelBuffer进行进一步处理
    // ...
} else {
    // 裁剪失败
    // ...
}

希望这可以帮助您实现将cvPixelBuffer裁剪为特定CGRect边界的功能。