public static ImageMap Convolve(ImageMap img, ConvLinearMask mask)
{
ImageMap res = new ImageMap(img.XDim, img.YDim);
ImageMap res2 = new ImageMap(img.XDim, img.YDim);
Convolve1D(res, mask, img, Direction.Vertical);
Convolve1D(res2, mask, res, Direction.Horizontal);
return(res2);
}
internal static double CalculateConvolutionValue1D(ImageMap src,
ConvLinearMask mask, int n, int p, int maxN, int maxP, Direction dir)
{
double sum = 0.0;
bool isOut = false;
double outBound = 0.0; // values that are out of bound
for (int xw = 0; xw < mask.Count; ++xw)
{
int curAbsP = xw - mask.Middle + p;
if (curAbsP < 0 || curAbsP >= maxP)
{
isOut = true;
outBound += mask[xw];
continue;
}
if (dir == Direction.Vertical)
{
sum += mask[xw] * src[n, curAbsP];
}
else
{
sum += mask[xw] * src[curAbsP, n];
}
}
if (isOut)
{
sum *= 1.0 / (1.0 - outBound);
}
return(sum);
}
public static void Convolve1D(ImageMap dest, ConvLinearMask mask,
ImageMap src, Direction dir)
{
int maxN; // outer loop maximum index 外环最大索引
int maxP; // inner loop maximum index 内环最大索引
if (dir == Direction.Vertical)
{
maxN = src.XDim;
maxP = src.YDim;
}
else if (dir == Direction.Horizontal)
{
maxN = src.YDim;
maxP = src.XDim;
}
else
{
throw (new Exception("TODO: invalid direction"));
}
for (int n = 0; n < maxN; ++n) //外环
{
for (int p = 0; p < maxP; ++p) //内环
{
double val = ConvolutionFilter.CalculateConvolutionValue1D(src, mask, n, p, maxN, maxP, dir);
if (dir == Direction.Vertical)
{
dest[n, p] = val;
}
else
{
dest[p, n] = val;
}
}
}
}
public GaussianConvolution(double sigma, int dim)
{
dim |= 1;
mask = new ConvLinearMask(dim);
double sigma2sq = 2 * sigma * sigma;
double normalizeFactor = 1.0 / (Math.Sqrt(2.0 * Math.PI) * sigma);
for (int n = 0; n < dim; ++n)
{
int relPos = n - mask.Middle;
double G = (relPos * relPos) / sigma2sq;
G = Math.Exp(-G);
G *= normalizeFactor;
mask[n] = G;
mask.MaskSum += G;
}
}