Trying to transform Kinect Depth from gray scale to RGB according to distance

Question

Im working with Kinect for a research project, and i was until now only messing with skeleton tracking. Now i went into the depths of the Depth Stream and i want to know how to create that RGB color scale we see in some depth streams. Mine is in gray scale. There is a part of the Depth Event that i dont understand and i feel this is very important to understand how it works, and how i could change it to color, its the definition of the intesity variable.

private void SensorDepthFrameReady(object sender, DepthImageFrameReadyEventArgs e){
        using (DepthImageFrame depthFrame = e.OpenDepthImageFrame())
        {
            if (depthFrame != null)
            {
                // Copy the pixel data from the image to a temporary array
                depthFrame.CopyDepthImagePixelDataTo(this.depthPixels);

                // Get the min and max reliable depth for the current frame
                int minDepth = depthFrame.MinDepth;
                int maxDepth = depthFrame.MaxDepth;

                // Convert the depth to RGB
                int colorPixelIndex = 0;              
                for (int i = 0; i < this.depthPixels.Length; ++i)
                {
                    // Get the depth for this pixel
                    short depth = depthPixels[i].Depth;

                    if (depth > 2000) depth = 0; //ive put this here just to test background elimination

                    byte intensity = (byte)(depth >= minDepth && depth <= maxDepth ? depth : 0);
                    //WHAT IS THIS LINE ABOVE DOING?

                    // Write out blue byte
                    this.colorPixels[colorPixelIndex++] = intensity;

                    // Write out green byte
                    this.colorPixels[colorPixelIndex++] = intensity;

                    // Write out red byte                        
                    this.colorPixels[colorPixelIndex++] = intensity;

                    // We're outputting BGR, the last byte in the 32 bits is unused so skip it
                    // If we were outputting BGRA, we would write alpha here.


                    ++colorPixelIndex;
                }
                // Write the pixel data into our bitmap
                this.colorBitmap.WritePixels(
                    new Int32Rect(0, 0, this.colorBitmap.PixelWidth, this.colorBitmap.PixelHeight),
                    this.colorPixels,
                    this.colorBitmap.PixelWidth * sizeof(int),
                    0);
            }
        }
}

Answer 1

byte intensity = (byte)(depth >= minDepth && depth <= maxDepth ? depth : 0);
//WHAT IS THIS LINE ABOVE DOING?

The line above is using the Ternary Operator

Basically its a one line if statement and is equivalent to:

byte intensity;

if (depth >= minDepth && depth <= maxDepth) 
{
    intensity = (byte)depth;
}
else
{
    intensity = 0;
}

The trick to colouring the depth image is to multiply the intensity by a tint colour. For example:

Color tint = Color.FromArgb(0, 255, 0) // Green

// Write out blue byte
this.colorPixels[colorPixelIndex++] = intensity * tint.B;

// Write out green byte
this.colorPixels[colorPixelIndex++] = intensity * tint.G;

// Write out red byte                        
this.colorPixels[colorPixelIndex++] = intensity * tint.R;