Question

如何从CVPixelBufferRef获取RGB（或任何其他格式）像素值？我尝试了很多方法，但还没有成功。

        func captureOutput(captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {

            let pixelBuffer: CVPixelBufferRef = CMSampleBufferGetImageBuffer(sampleBuffer)!
            CVPixelBufferLockBaseAddress(pixelBuffer, 0)
            let baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer)


    //Get individual pixel values here

    CVPixelBufferUnlockBaseAddress(pixelBuffer, 0)
        }

Answer 1

baseAddress是一个不安全的可变指针，更确切地说是UnsafeMutablePointer<Void>。将指针从Void转换为更具体的类型后，您可以轻松访问内存：

// Convert the base address to a safe pointer of the appropriate type
let byteBuffer = UnsafeMutablePointer<UInt8>(baseAddress)

// read the data (returns value of type UInt8)
let firstByte = byteBuffer[0]

// write data
byteBuffer[3] = 90

确保使用正确的类型（8,16或32位无符号整数）。这取决于视频格式。最有可能是8位。

缓冲区格式更新：

您可以在初始化AVCaptureVideoDataOutput实例时指定格式。你基本上可以选择：

BGRA：蓝色，绿色，红色和alpha值以32位整数存储的单个平面
420YpCbCr8BiPlanarFullRange：两个平面，第一个包含每个像素的字节，具有Y（亮度）值，第二个包含像素组的Cb和Cr（色度）值
420YpCbCr8BiPlanarVideoRange：与420YpCbCr8BiPlanarFullRange相同，但Y值限制在16 - 235范围内（由于历史原因）

如果您对颜色值感兴趣并且速度（或者说最大帧速率）不是问题，那么请选择更简单的BGRA格式。否则采用一种更有效的原生视频格式。

如果你有两架飞机，你必须得到所需飞机的基地址（见视频格式示例）：

视频格式示例

let pixelBuffer: CVPixelBufferRef = CMSampleBufferGetImageBuffer(sampleBuffer)!
CVPixelBufferLockBaseAddress(pixelBuffer, 0)
let baseAddress = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0)
let bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0)
let byteBuffer = UnsafeMutablePointer<UInt8>(baseAddress)

// Get luma value for pixel (43, 17)
let luma = byteBuffer[17 * bytesPerRow + 43]

CVPixelBufferUnlockBaseAddress(pixelBuffer, 0)

BGRA示例

let pixelBuffer: CVPixelBufferRef = CMSampleBufferGetImageBuffer(sampleBuffer)!
CVPixelBufferLockBaseAddress(pixelBuffer, 0)
let baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer)
let int32PerRow = CVPixelBufferGetBytesPerRow(pixelBuffer)
let int32Buffer = UnsafeMutablePointer<UInt32>(baseAddress)

// Get BGRA value for pixel (43, 17)
let luma = int32Buffer[17 * int32PerRow + 43]

CVPixelBufferUnlockBaseAddress(pixelBuffer, 0)

Answer 2

Swift3的更新：

let pixelBuffer: CVPixelBufferRef = CMSampleBufferGetImageBuffer(sampleBuffer)!
CVPixelBufferLockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0));
let int32Buffer = unsafeBitCast(CVPixelBufferGetBaseAddress(pixelBuffer), to: UnsafeMutablePointer<UInt32>.self)
let int32PerRow = CVPixelBufferGetBytesPerRow(pixelBuffer)
// Get BGRA value for pixel (43, 17)
let luma = int32Buffer[17 * int32PerRow + 43]

CVPixelBufferUnlockBaseAddress(pixelBuffer, 0)

Answer 3

除了Codos的回答，这里有一个从BRGA像素缓冲区获取各个rgb值的方法。注意：在调用之前必须锁定缓冲区。

func pixelFrom(x: Int, y: Int, movieFrame: CVPixelBuffer) -> (UInt8, UInt8, UInt8) {
    let baseAddress = CVPixelBufferGetBaseAddress(movieFrame)

    let width = CVPixelBufferGetWidth(movieFrame)
    let height = CVPixelBufferGetHeight(movieFrame)

    let bytesPerRow = CVPixelBufferGetBytesPerRow(movieFrame)
    let buffer = baseAddress!.assumingMemoryBound(to: UInt8.self)

    let index = x+y*bytesPerRow
    let b = buffer[index]
    let g = buffer[index+1]
    let r = buffer[index+2]

    return (r, g, b)
}

Answer 4

快速5

我遇到了同样的问题，并得到以下解决方案。我的CVPixelBuffer的尺寸为68 x 68，可以通过

检查

CVPixelBufferLockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0))
print(CVPixelBufferGetWidth(pixelBuffer))
print(CVPixelBufferGetHeight(pixelBuffer))

您还必须知道每行的字节数：

print(CVPixelBufferGetBytesPerRow(pixelBuffer))

在我的情况下为320。

此外，您需要了解像素缓冲区的数据类型，这对我来说是Float32。

然后，我构造了一个字节缓冲区，并按如下所示连续读取字节（请记住，如上所示锁定基地址）：

var byteBuffer = unsafeBitCast(CVPixelBufferGetBaseAddress(pixelBuffer), to: UnsafeMutablePointer<Float32>.self)
var pixelArray: Array<Array<Float>> = Array(repeating: Array(repeating: 0, count: 68), count: 68)
for row in 0...67{
    for col in 0...67{
        pixelArray[row][col] = byteBuffer.pointee
        byteBuffer = byteBuffer.successor()    
    }
    byteBuffer = byteBuffer.advanced(by: 12)
}
CVPixelBufferUnlockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0))

您可能会对byteBuffer = byteBuffer.advanced(by: 12)部分感到好奇。我们必须这样做的原因如下。

我们知道每行有320个字节。但是，我们的缓冲区的宽度为68，数据类型为Float32，例如每个值4个字节。这意味着我们实际上每行只有272个字节，后跟零填充。零填充可能有内存布局方面的原因。

因此，我们必须跳过byteBuffer = byteBuffer.advanced(by: 12)（12*4 = 48）完成的每一行的最后48个字节。

此方法与其他解决方案有所不同，因为我们使用指向下一个byteBuffer的指针。但是，我发现这更简单，更直观。

从Swift中的CVPixelBufferRef获取像素值

4 个答案: