Class PaletteOptions

Namespace

Egami.Quantization

Assembly

Egami.dll

How formats with at most 256 colors (GIF, PNG with a palette, and indexed BMP and TGA) build their palette when an image has more colors than fit. Images with few enough colors always keep them exactly, without dithering.

public sealed record PaletteOptions : IEquatable<PaletteOptions>

Inheritance

object

PaletteOptions

Implements

IEquatable<PaletteOptions>

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Examples

using FileStream output = File.Create("duck.gif");
photo.Save(output, GifFormat.Info, new GifWriterOptions
{
    Palette = new PaletteOptions { MaxColors = 128, Dither = DitherMode.Ordered }, // FloydSteinberg (default), Ordered or None
    PaletteScope = GifPaletteScope.PerFrame,   // Auto (default): one table when all frames fit, else one per frame
});

Properties

AlphaThreshold

Gets the alpha below which a pixel is transparent, for formats whose transparency is on or off (GIF). Defaults to 128.

public byte AlphaThreshold { get; init; }

Property Value

byte

Default

Gets the default options: 256 colors, Floyd–Steinberg dithering at full strength, alpha threshold 128.

public static PaletteOptions Default { get; }

Property Value

PaletteOptions

Dither

Gets how mapping error is spread. Defaults to FloydSteinberg.

public DitherMode Dither { get; init; }

Property Value

DitherMode

Exceptions

ArgumentOutOfRangeException

The value is not a defined DitherMode.

DitherStrength

Gets how strongly the dither works, from 0 (none: the nearest color) to 1 (the default, full strength): the share of the error that is diffused, or the height of the ordered pattern.

public float DitherStrength { get; init; }

Property Value

float

Exceptions

ArgumentOutOfRangeException

The value is outside 0 to 1.

ExactMatching

Gets whether each color is matched to its exact nearest palette color. By default a 64-level lookup table answers for each small cube of colors at once, which is faster and can pick a color that is not quite the nearest; the default keeps every 1.x output unchanged.

public bool ExactMatching { get; init; }

Property Value

bool

FixedPalette

Gets a fixed palette to map to instead of building one, or null (the default) to build one from the image. Every writer that takes these options honours it, and throws when the palette has more colors than its format allows.

public Palette? FixedPalette { get; init; }

Property Value

Palette

Kernel

Gets a custom error-diffusion kernel used instead of Dither, or null (the default).

public ErrorDiffusionKernel? Kernel { get; init; }

Property Value

ErrorDiffusionKernel

MaxColors

Gets the most colors the palette may have, 2 to 256. Defaults to 256; a transparent entry counts as one.

public int MaxColors { get; init; }

Property Value

int

Exceptions

ArgumentOutOfRangeException

The value is outside 2 to 256.

RefineIterations

Gets how many k-means passes polish the built palette, moving each color to the mean of the pixels nearest it (Lloyd's algorithm on every fourth pixel), from 0 (the default) to 32. 4 to 8 passes gain a few tenths of a decibel at some cost; they never make the palette fit worse.

public int RefineIterations { get; init; }

Property Value

int

Exceptions

ArgumentOutOfRangeException

The value is outside 0 to 32.

Serpentine

Gets whether error diffusion alternates direction from row to row (serpentine scanning), which breaks up the diagonal streaks plain left-to-right diffusion can leave. Defaults to false.

public bool Serpentine { get; init; }

Property Value

bool