/// <summary>
/// Create a new NoiseMap from the given source NoiseMap using bilinear filtering.
///
/// When the sample is outside the source BorderValue is used by default. If <see cref="clamp"/>/>
/// is set clamping is used instead.
/// </summary>
/// <param name="src">The source NoiseMap</param>
/// <param name="width">Width of the new NoiseMap</param>
/// <param name="height">Height of the new NoiseMap</param>
/// <param name="clamp">Use clamping when the sample is outside the source NoiseMap</param>
/// <returns>The new NoiseMap</returns>
public static NoiseMap BilinearFilter(NoiseMap src, int width, int height, bool clamp = false)
{
var dest = new NoiseMap(width, height);
var xratio = (float)src.Width / dest.Width;
var yratio = (float)src.Height / dest.Height;
Parallel.For(0, dest.Height, y =>
{
for (var x = 0; x < dest.Width; ++x)
{
var u = (x + 0.5f) * xratio - 0.5f;
var v = (y + 0.5f) * yratio - 0.5f;
var x0 = NoiseMath.FastFloor(u);
var y0 = NoiseMath.FastFloor(v);
var x1 = x0 + 1;
var y1 = y0 + 1;
var xf = u - x0;
var yf = v - y0;
if (clamp)
{
x0 = NoiseMath.Clamp(x0, 0, src.Width - 1);
x1 = NoiseMath.Clamp(x1, 0, src.Width - 1);
y0 = NoiseMath.Clamp(y0, 0, src.Height - 1);
y1 = NoiseMath.Clamp(y1, 0, src.Height - 1);
}
var c00 = src.GetValue(x0, y0);
var c01 = src.GetValue(x0, y1);
var c10 = src.GetValue(x1, y0);
var c11 = src.GetValue(x1, y1);
var val = NoiseMath.Bilinear(xf, yf, c00, c01, c10, c11);
dest.SetValue(x, y, val);
}
});
return(dest);
}
