convolutionShaderBuildKernel function

List<num> convolutionShaderBuildKernel(
  1. double sigma
)

Implementation

List<num> convolutionShaderBuildKernel(double sigma) {
  // We lop off the sqrt(2 * pi) * sigma term, since we're going to normalize anyway.

  double gauss(double x, double sigma) {
    return math.exp(-(x * x) / (2.0 * sigma * sigma));
  }

  int i;
  List<num> values;
  double sum;
  double halfWidth;
  int kMaxKernelSize = 25;
  int kernelSize = (2 *(sigma * 3.0).ceil() + 1).toInt();

  if (kernelSize > kMaxKernelSize) kernelSize = kMaxKernelSize;
  halfWidth = (kernelSize - 1) * 0.5;

  values = List<num>.filled(kernelSize, 0.0);
  sum = 0.0;
  for (i = 0; i < kernelSize; ++i) {
    values[i] = gauss(i - halfWidth, sigma);
    sum += values[i];
  }

  // normalize the kernel

  for (i = 0; i < kernelSize; ++i){
    values[i] /= sum;
  }

  return values;
}