public RangeFit(ColourSet colours, CompressionOptions flags) : base(colours)
{
// initialise the metric
bool perceptual = ((flags & CompressionOptions.ColourMetricPerceptual) != 0);
m_metric = perceptual ? new Vec3(0.2126f, 0.7152f, 0.0722f) : Vec3.One;
// initialise the best error
m_besterror = float.MaxValue;
// cache some values
var count = m_colours.Count;
var values = m_colours.Points;
var weights = m_colours.Weights;
// get the covariance matrix
Sym3x3 covariance = Sym3x3.ComputeWeightedCovariance(count, values, weights);
// compute the principle component
Vec3 principle = Sym3x3.ComputePrincipleComponent(covariance);
// get the min and max range as the codebook endpoints
Vec3 start = Vec3.Zero;
Vec3 end = Vec3.Zero;
if (count > 0)
{
float min, max;
// compute the range
start = end = values[0];
min = max = Vec3.Dot(values[0], principle);
for (int i = 1; i < count; ++i)
{
float val = Vec3.Dot(values[i], principle);
if (val < min)
{
start = values[i];
min = val;
}
else if (val > max)
{
end = values[i];
max = val;
}
}
}
// clamp the output to [0, 1]
start = start.Clamp(Vec3.Zero, Vec3.One);
end = end.Clamp(Vec3.Zero, Vec3.One);
// clamp to the grid and save
m_start = (GRID * start + HALF).Truncate() * GRIDRCP;
m_end = (GRID * end + HALF).Truncate() * GRIDRCP;
}
public SingleColourFit(ColourSet colours, CompressionOptions flags) : base(colours)
{
// grab the single colour
var values = m_colours.Points;
m_colour[0] = (Byte)((255.0f * values[0].X).FloatToInt(255));
m_colour[1] = (Byte)((255.0f * values[0].Y).FloatToInt(255));
m_colour[2] = (Byte)((255.0f * values[0].Z).FloatToInt(255));
// initialise the best error
m_besterror = int.MaxValue;
}
public ClusterFitAlt(ColourSet colours, CompressionOptions flags) : base(colours)
{
// initialise the metric
bool perceptual = ((flags & CompressionOptions.ColourMetricPerceptual) != 0);
m_metric = perceptual ? new Vec4(0.2126f, 0.7152f, 0.0722f, 1) : Vec4.One;
m_metricSqr = m_metric * m_metric;
// get the covariance matrix
var covariance = Sym3x3.ComputeWeightedCovariance(m_colours.Count, m_colours.Points, m_colours.Weights, m_metric.GetVec3());
// compute the principle component
m_principle = Sym3x3.ComputePrincipleComponent(covariance);
}
/// <summary>
/// Compresses a 4x4 block of pixels.
/// </summary>
/// <remarks>
/// The source pixels should be presented as a contiguous array of 16 rgba
/// values, with each component as 1 byte each. In memory this should be:
///
/// { r1, g1, b1, a1, .... , r16, g16, b16, a16 }
///
/// The mask parameter enables only certain pixels within the block. The lowest
/// bit enables the first pixel and so on up to the 16th bit. Bits beyond the
/// 16th bit are ignored. Pixels that are not enabled are allowed to take
/// arbitrary colours in the output block. An example of how this can be used
/// is in the CompressImage function to disable pixels outside the bounds of
/// the image when the width or height is not divisible by 4.
///
/// The flags parameter should specify either kDxt1, kDxt3 or kDxt5 compression,
/// however, DXT1 will be used by default if none is specified. When using DXT1
/// compression, 8 bytes of storage are required for the compressed DXT block.
/// DXT3 and DXT5 compression require 16 bytes of storage per block.
///
/// The flags parameter can also specify a preferred colour compressor and
/// colour error metric to use when fitting the RGB components of the data.
/// Possible colour compressors are: kColourClusterFit (the default),
/// kColourRangeFit or kColourIterativeClusterFit. Possible colour error metrics
/// are: kColourMetricPerceptual (the default) or kColourMetricUniform. If no
/// flags are specified in any particular category then the default will be
/// used. Unknown flags are ignored.
///
/// When using kColourClusterFit, an additional flag can be specified to
/// weight the colour of each pixel by its alpha value. For images that are
/// rendered using alpha blending, this can significantly increase the
/// perceived quality.
/// </remarks>
/// <param name="rgba">The rgba values of the 16 source pixels.</param>
/// <param name="mask">The valid pixel mask.</param>
/// <param name="flags">Compression flags.</param>
public void CompressMasked(Byte[] rgba, int mask, CompressionOptions options)
{
System.Diagnostics.Debug.Assert(rgba != null && rgba.Length == 64, nameof(rgba));
// fix any bad flags
options = options.FixFlags();
// create the minimal point set
var colours = new ColourSet(rgba, mask, _Mode, options);
// check the compression type and compress colour
if (colours.Count == 1)
{
// always do a single colour fit
var fit = new SingleColourFit(colours, options);
fit.Compress(this);
}
else if ((options & CompressionOptions.ColourRangeFit) != 0 || colours.Count == 0)
{
// do a range fit
var fit = new RangeFit(colours, options);
fit.Compress(this);
}
else
{
if ((options & CompressionOptions.ColourClusterFitAlt) != 0)
{
var fit = new ClusterFitAlt(colours, options);
fit.Compress(this);
}
else
{
// default to a cluster fit (could be iterative or not)
var fit = new ClusterFit(colours, options);
fit.Compress(this);
}
}
// compress alpha separately if necessary
if ((_Mode & CompressionMode.Dxt3) != 0)
{
this.CompressAlphaDxt3(rgba, mask);
}
else if ((_Mode & CompressionMode.Dxt5) != 0)
{
this.CompressAlphaDxt5(rgba, mask);
}
}
public ClusterFit(ColourSet colours, CompressionOptions flags) : base(colours)
{
// set the iteration count
m_iterationCount = (flags & CompressionOptions.ColourIterativeClusterFit) != 0 ? MAXITERATIONS : 1;
// initialise the metric
bool perceptual = ((flags & CompressionOptions.ColourMetricPerceptual) != 0);
m_metric = perceptual ? PERCEPTUAL : Vec4.One;
// get the covariance matrix
var covariance = Sym3x3.ComputeWeightedCovariance(m_colours.Count, m_colours.Points, m_colours.Weights);
// compute the principle component
m_principle = Sym3x3.ComputePrincipleComponent(covariance);
}
public ClusterFit(ColourSet colours, CompressionOptions flags) : base(colours)
{
// set the iteration count
m_iterationCount = (flags & CompressionOptions.ColourIterativeClusterFit) != 0 ? MAXITERATIONS : 1;
// initialise the metric
bool perceptual = ((flags & CompressionOptions.ColourMetricPerceptual) != 0);
m_metric = perceptual ? new Vec4(0.2126f, 0.7152f, 0.0722f, 0.0f) : Vec4.One;
// cache some values
var count = m_colours.Count;
var values = m_colours.Points;
// get the covariance matrix
Sym3x3 covariance = Sym3x3.ComputeWeightedCovariance(count, values, m_colours.Weights);
// compute the principle component
m_principle = Sym3x3.ComputePrincipleComponent(covariance);
}
public ColourFit(ColourSet colours)
{
m_colours = colours;
}