/// <summary>
/// For a given color, gives information about a blob within the given bitmap that is that color
/// </summary>
/// <param name="bitmap">The bitmap containing the blob</param>
/// <param name="color">The color of the blob</param>
/// <returns>An ImageBlobInfo object containing information of the blob of the given color</returns>
public ImageBlobInfo(WriteableBitmap bitmap, Color color)
{
Color = color;
Area = 0;
Centroid = new Point(0, 0);
SecondRowMoment = 0;
SecondMixedMoment = 0;
SecondColumnMoment = 0;
MaxInertia = 0;
MinInertia = 0;
Circularity = 0;
Perimeter = 0;
int stride = (bitmap.PixelWidth * bitmap.Format.BitsPerPixel + 7) / 8;
int height = bitmap.PixelHeight;
int width = bitmap.PixelWidth;
byte[] pixelArray = new byte[bitmap.PixelHeight * stride];
bitmap.CopyPixels(pixelArray, stride, 0);
// Calculate Area and Centroid
double r = 0;
double c = 0;
for (int row = 0; row < height; row++)
{
for (int column = 0; column < width; column++)
{
int index = row * stride + 4 * column;
var pixel = Pixel.GetPixel(pixelArray, index);
if (pixel.Color == color)
{
Area++;
r += row; // add the row number
c += column; // add the column number
}
}
}
Centroid = new Point(c / Area, r / Area);
// Calculate Second-Order Moments
for (int row = 0; row < height; row++)
{
for (int column = 0; column < width; column++)
{
int index = row * stride + 4 * column;
var pixel = Pixel.GetPixel(pixelArray, index);
if (pixel.Color == color)
{
SecondRowMoment += Math.Pow(row - Centroid.Y, 2);
SecondMixedMoment += (row - Centroid.Y) * (column - Centroid.X);
SecondColumnMoment += Math.Pow(column - Centroid.X, 2);
}
}
}
SecondRowMoment /= Area;
SecondMixedMoment /= Area;
SecondColumnMoment /= Area;
// Calculate Inertia
var theta = (2 * SecondMixedMoment) / (SecondColumnMoment - SecondRowMoment);
theta = Math.Atan(theta);
theta /= 2;
var otherTheta = theta + Math.PI / 2;
var inertiaOne = Math.Pow(Math.Sin(theta), 2) * SecondColumnMoment +
Math.Sin(theta) * Math.Cos(theta) * SecondMixedMoment +
Math.Pow(Math.Cos(theta), 2) * SecondRowMoment;
var inertiaTwo = Math.Pow(Math.Sin(otherTheta), 2) * SecondColumnMoment +
Math.Sin(otherTheta) * Math.Cos(otherTheta) * SecondMixedMoment +
Math.Pow(Math.Cos(otherTheta), 2) * SecondRowMoment;
MaxInertia = Math.Max(inertiaOne, inertiaTwo);
MinInertia = Math.Min(inertiaOne, inertiaTwo);
// Calculate Circulator
double mean = 0;
for (int row = 0; row < height; row++)
{
for (int column = 0; column < width; column++)
{
int index = row * stride + 4 * column;
var pixel = Pixel.GetPixel(pixelArray, index);
if (pixel.Color == color)
{
mean += Math.Sqrt(Math.Pow(column - Centroid.X, 2) + Math.Pow(row - Centroid.Y, 2));
}
}
}
mean /= Area;
double standardDeviation = 0;
for (int row = 0; row < height; row++)
{
for (int column = 0; column < width; column++)
{
int index = row * stride + 4 * column;
var pixel = Pixel.GetPixel(pixelArray, index);
if (pixel.Color == color)
{
var value = Math.Sqrt(Math.Pow(column - Centroid.X, 2) + Math.Pow(row - Centroid.Y, 2));
value -= mean;
value = Math.Pow(value, 2);
standardDeviation += value;
}
}
}
standardDeviation /= Area;
standardDeviation = Math.Sqrt(standardDeviation);
Circularity = mean / standardDeviation;
// Calculate Perimeter
var filteredBitmap = BitmapColorer.EraseAllButCertainColor(bitmap, color);
var perimeterBitmap = BitmapOperations.GetPerimeterBitmap(filteredBitmap);
byte[] perimeterPixelArray = new byte[perimeterBitmap.PixelHeight * stride];
perimeterBitmap.CopyPixels(perimeterPixelArray, stride, 0);
var perimeterPixelList = BitmapOperations.BuildPerimeterPath(perimeterPixelArray, bitmap.PixelHeight, bitmap.PixelWidth, stride);
for (int i = 0; i < perimeterPixelList.Count; i++)
{
int comparisonIndex = i + 1;
if (i == perimeterPixelList.Count - 1)
{
comparisonIndex = 0;
}
// If the current pixel and the next pixel are vertical or horizontal neighbors
if (perimeterPixelList[i] == perimeterPixelList[comparisonIndex] + stride ||
perimeterPixelList[i] == perimeterPixelList[comparisonIndex] - stride ||
perimeterPixelList[i] == perimeterPixelList[comparisonIndex] - 4 ||
perimeterPixelList[i] == perimeterPixelList[comparisonIndex] + 4)
{
Perimeter++;
}
// If the current pixel and the next pixel are diagonal neighbors
else if (perimeterPixelList[i] == perimeterPixelList[comparisonIndex] + stride + 4 ||
perimeterPixelList[i] == perimeterPixelList[comparisonIndex] + stride - 4 ||
perimeterPixelList[i] == perimeterPixelList[comparisonIndex] - stride + 4 ||
perimeterPixelList[i] == perimeterPixelList[comparisonIndex] - stride - 4)
{
Perimeter += 1.4;
}
}
}