private static ProfileCurve curveFromParameters(double a, double b, double c, double d, double e, double f, double g)
{
if (
g.IsRoughlyEqualTo(2.4) &&
d.IsRoughlyEqualTo(0.04045) &&
a.IsRoughlyEqualTo(1.000 / 1.055) &&
b.IsRoughlyEqualTo(0.055 / 1.055) &&
c.IsRoughlyEqualTo(1.000 / 12.92)
)
{
return(sRGB.Curve);
}
var igt = new float[LookupTables.InverseGammaLength];
for (int i = 0; i < igt.Length; i++)
{
double val = (double)i / LookupTables.InverseGammaScale;
if (val >= d)
{
val = Math.Pow(val * a + b, g) + c + e;
}
else
{
val = val * c + f;
}
igt[i] = (float)val;
}
g = 1d / g;
var gt = new float[LookupTables.GammaLengthFloat];
for (int i = 0; i < gt.Length; i++)
{
double val = (double)i / LookupTables.GammaScaleFloat;
if (val > (c * d + f))
{
val = (Math.Pow(val - c - e, g) - b) / a;
}
else
{
val = c == 0f ? 0f : ((val - f) / c);
}
gt[i] = (float)val;
}
LookupTables.Fixup(gt, LookupTables.GammaScaleFloat);
LookupTables.Fixup(igt, LookupTables.InverseGammaScale);
return(new ProfileCurve(gt, igt));
}
private static ProfileCurve curveFromPower(double gamma)
{
var igt = new float[LookupTables.InverseGammaLength];
for (int i = 0; i < igt.Length; i++)
{
igt[i] = (float)Math.Pow((double)i / LookupTables.InverseGammaScale, gamma);
}
gamma = 1d / gamma;
var gt = new float[LookupTables.GammaLengthFloat];
for (int i = 0; i < gt.Length; i++)
{
gt[i] = (float)Math.Pow((double)i / LookupTables.GammaScaleFloat, gamma);
}
LookupTables.Fixup(gt, LookupTables.GammaScaleFloat);
LookupTables.Fixup(igt, LookupTables.InverseGammaScale);
return(new ProfileCurve(gt, igt));
}
private static ProfileCurve curveFromPoints(ReadOnlySpan <ushort> points, bool inverse)
{
int buffLen = points.Length * sizeof(double);
using var buff = MemoryPool <byte> .Shared.Rent(buffLen);
var curve = MemoryMarshal.Cast <byte, double>(buff.Memory.Span.Slice(0, buffLen));
double cscal = curve.Length - 1;
for (int i = 0; i < curve.Length; i++)
{
curve[i] = (double)points[i] / ushort.MaxValue;
}
var igt = new float[LookupTables.InverseGammaLength];
for (int i = 0; i <= LookupTables.InverseGammaScale; i++)
{
double val = (double)i / LookupTables.InverseGammaScale;
double pos = val * cscal;
int idx = Math.Min((int)pos, curve.Length - 2);
igt[i] = (float)Lerp(curve[idx], curve[idx + 1], pos - idx);
}
if (lutInvertsTo(igt, LookupTables.SrgbGamma))
{
return(sRGB.Curve);
}
if (inverse)
{
curve.Reverse();
}
var gt = new float[LookupTables.GammaLengthFloat];
for (int i = 0; i <= LookupTables.GammaScaleFloat; i++)
{
double val = (double)i / LookupTables.GammaScaleFloat;
int idx = curve.BinarySearch(val);
double pos;
if (idx >= 0)
{
pos = idx;
}
else
{
idx = ~idx;
if (idx == 0)
{
pos = 0;
}
else if (idx == curve.Length)
{
pos = curve.Length - 1;
}
else
{
double vh = curve[idx];
double vl = curve[idx - 1];
if (vl == vh)
{
pos = idx;
}
else
{
pos = idx - 1 + (val - vl) / (vh - vl);
}
}
}
gt[i] = (float)(pos / (curve.Length - 1));
}
if (inverse)
{
Array.Reverse(gt, 0, LookupTables.GammaScaleFloat + 1);
}
LookupTables.Fixup(gt, LookupTables.GammaScaleFloat);
LookupTables.Fixup(igt, LookupTables.InverseGammaScale);
return(new ProfileCurve(gt, igt));
}
public WideningImpl(bool videoRange = false)
{
scale = 1f / (videoRange ? VideoLumaScale : byte.MaxValue);
offset = videoRange ? VideoLumaMin : 0f;
valueTable = videoRange ? LookupTables.MakeVideoInverseGamma(LookupTables.Alpha) : LookupTables.Alpha;
}
