Question

我正在尝试在Kinect v2中获取每个CameraSpacePoint的RGB值。在尝试访问转换后的帧数据时，代码正在抛出IndexOutOfRangeException。我发现以下行引发了这个错误：

byte red   = pixels[4 * pixelsBaseIndex + 0];
byte green = pixels[4 * pixelsBaseIndex + 1];
byte blue  = pixels[4 * pixelsBaseIndex + 2];
byte alpha = pixels[4 * pixelsBaseIndex + 3];

请参阅以下完整代码：

int depthWidth = kinectSensor.DepthFrameSource.FrameDescription.Width;
int depthHeight = kinectSensor.DepthFrameSource.FrameDescription.Height;
int colorWidth = kinectSensor.ColorFrameSource.FrameDescription.Width;
int colorHeight = kinectSensor.ColorFrameSource.FrameDescription.Height;

ushort[] depthData = new ushort[depthWidth * depthHeight];
CameraSpacePoint[] cameraPoints = new CameraSpacePoint[depthData.Length];
ColorSpacePoint[] colorPoints = new ColorSpacePoint[depthData.Length];

// Assuming RGBA format here
byte[] pixels = new byte[colorWidth * colorHeight * 4];

depthFrame = multiSourceFrame.DepthFrameReference.AcquireFrame();
colorFrame = multiSourceFrame.ColorFrameReference.AcquireFrame();

if ((depthFrame == null) || (colorFrame == null))
{
    return;
}

depthFrame.CopyFrameDataToArray(depthData);
coordinateMapper.MapDepthFrameToCameraSpace(depthData, cameraPoints);
coordinateMapper.MapDepthFrameToColorSpace(depthData, colorPoints);

// We are using RGBA format
colorFrame.CopyConvertedFrameDataToArray(pixels, ColorImageFormat.Rgba);

for (var index = 0; index < depthData.Length; index++)
{
    var u = colorPoints[index].X;
    var v = colorPoints[index].Y;

    if (u < 0 || u >= colorWidth || v < 0 || v >= colorHeight) continue;

    int pixelsBaseIndex = (int)(v * colorWidth + u);
    try
    {
        byte red = pixels[4 * pixelsBaseIndex + 0];
        byte green = pixels[4 * pixelsBaseIndex + 1];
        byte blue = pixels[4 * pixelsBaseIndex + 2];
        byte alpha = pixels[4 * pixelsBaseIndex + 3];
    }
    catch (IndexOutOfRangeException ex)
    {
        int minValue = 4 * pixelsBaseIndex;
        int maxValue = 4 * pixelsBaseIndex + 3;
        Console.WriteLine((minValue > 0) + ", " + (maxValue < pixels.Length));
    }
}

代码看起来很好但是我不确定我在这里缺少什么！ 如何避免IndexOutOfRangeException例外？有任何建议吗？

Answer 1

First thing pixelsBaseIndex =< 2070601 (2070601 = 1919 * 1079)

2074817 is an invalid value for the pixelsBaseIndex.

This error could be somewhere here.

if (u < 0 || u >= colorWidth || v < 0 || v >= colorHeight) continue;

int pixelsBaseIndex = (int)(v * colorWidth + u);

Best thing is to console log u, v, colorWidth, colorHeight and validate them.

EDIT

As i suspected, it is caused by the Floating-Point Arithmetic. Mapping one frame to another frame needs complex matrix calculations, thus u,v get floating point values. Keep in mind that u,v are the pixel coordinates of the color space. They must be non-negative integers.

My recommended solution is

...
    int u = (int) Math.Floor(colorPoints[index].X);
    int v = (int) Math.Floor(colorPoints[index].Y);

    if (u < 0 || u >= colorWidth || v < 0 || v >= colorHeight) continue;
...

FYI

Check out following lines of code to understand why u, v pixel coordinates getting floating point values. The decision, taking the floor or discarding the invalid values, is depending on the developer since in either cases, you are loosing some sort of information. For example, taking the floor means you are taking the color of the nearest pixel.

In my personal option, out putting more precise value (thus floating point value) is important for developers who do more calculations on the outputted values.For example, point cloud registration.

depth_to_color

calculating x offset for rgb image based on depth value

尝试从C＃中的Kinect v2获取颜色值时的IndexOutOfRange异常

1 个答案: