Question

我正在尝试通过使用AVFoundation框架获取照片亮度/亮度的平均值。我正在做的是从AVCapturePhoto对象获取像素缓冲区（仅带有RAW捕获），通过制作UnsafeMutablePointer并在特定点获取亮度值来访问其像素。我期望得到的平均值应该在528和4095之间（黑白水平）。我不确定从此缓冲区获得什么样的价值，以及我是否以正确的方式访问其像素。我也不确定这是否是最好的方法，但是我从图像本身获得的绿色值似乎是压缩值，因为它永远不会超过255。

下面是我正在使用的代码：

        // The pixel buffer stores an image in main memory.
        let pixelBuffer = photo.pixelBuffer!

        // Locks the BaseAddress of the PixelBuffer to ensure that the memory is accessible.
        CVPixelBufferLockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0))

        // Buffer width and height
        let bufferWidth = CVPixelBufferGetWidth(pixelBuffer) // 4032
        let bufferHeight = CVPixelBufferGetHeight(pixelBuffer) // 3024

        /*
         Returns the base address of the PixelBuffer.
         Retrieving the base address for a PixelBuffer requires that the buffer base address be locked via a successful call to CVPixelBufferLockBaseAddress.
         */

        let baseAddress = CVPixelBufferGetBaseAddress(pixelBuffer)
        let bytesPerRow = CVPixelBufferGetBytesPerRow(pixelBuffer) // 8064

        /*
         Returns the bits of the given instance, interpreted as having the specified type.
         Use this function only to convert the instance passed as x to a layout-compatible type when conversion through other means is not possible.
         */

        let pointer = unsafeBitCast(pixelBuffer, to: UnsafeMutablePointer<UInt16>.self) // what data type to use?
        //let pointer = baseAddress?.bindMemory(to: UInt16.self, capacity: CVPixelBufferGetDataSize(pixelBuffer))
        var lumaSum: Double = 0.0

        for y in 0..<bufferHeight {
            for x in 0..<bufferWidth {
                let index = y * bufferWidth + x // or y * bytesPerRow + x
                let luma = Double(pointer[index])
                lumaSum += luma
            }
        }

        let average = lumaSum / Double(bufferWidth * bufferHeight)
        print(average)

        CVPixelBufferUnlockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0))

以下是一些有用的信息：

像素格式：kCVPixelFormatType_14Bayer_RGGB ='rgg4'，/ *拜耳14位Little-Endian，打包为16位，已排序R G R G ...与G B G B ...... /

缓冲区数据大小：24385600

包含RGB：true

每个组件的位数：8

每行字节数：8064

每块位数：16

从原始图像数据获取像素亮度

0 个答案: