Table of Contents

Class Ktx2WriterOptions

Namespace
Egami.Formats.Extended.Ktx
Assembly
Egami.Formats.Extended.dll

Options for writing KTX 2.

public sealed class Ktx2WriterOptions : WriterOptions
Inheritance
Ktx2WriterOptions
Inherited Members

Examples

// With no options: the nearest uncompressed format (R8G8B8A8_SRGB for 8-bit colour) and the full mip chain.
using (FileStream output = File.Create("duck.ktx2"))
{
    image.Save(output, Ktx2Format.Info);
}

// A GPU block format: BC7 for desktop, ASTC or ETC2 for mobile; effort runs 0 (fastest) to 6 (best).
using (FileStream output = File.Create("duck-astc.ktx2"))
{
    image.Save(output, Ktx2Format.Info, new Ktx2WriterOptions { Format = KtxTextureFormat.Astc6x6, Effort = 3 });
}

// Basis Universal, which a viewer transcodes to whatever its GPU reads: UASTC with RDO and Zstandard (glTF's usual
// pick), or ETC1S for the smallest files.
using (FileStream output = File.Create("duck-uastc.ktx2"))
{
    image.Save(output, Ktx2Format.Info, new Ktx2WriterOptions
    {
        Format = KtxTextureFormat.Uastc,
        UastcRdo = 2,
        Supercompression = KtxSupercompression.Zstandard,
    });
}

using (FileStream output = File.Create("duck-etc1s.ktx2"))
{
    image.Save(output, Ktx2Format.Info, new Ktx2WriterOptions { Format = KtxTextureFormat.Etc1s, BasisQuality = 128 });
}

// Six faces into a cube map; SaveAll without Cube writes a texture array.
using RasterList faces = Raster.LoadAll("sky.ktx2", context);
using (FileStream output = File.Create("sky-bc1.ktx2"))
{
    Raster.SaveAll(faces, output, Ktx2Format.Info, new Ktx2WriterOptions { Cube = true, Format = KtxTextureFormat.Bc1 });
}

Remarks

Re-saving a raster loaded from KTX or KTX 2 keeps its format and sRGB flag for every option left at null when the writer writes that format; a raster loaded from DDS keeps its block format the same way.

Properties

BasisQuality

Gets the quality of Etc1s, 1 to 255: it sets the size of the endpoint and selector codebooks, from 16 entries to 16128. Defaults to 128 (about 1000 entries).

public int BasisQuality { get; init; }

Property Value

int

Exceptions

ArgumentOutOfRangeException

The value is outside 1 to 255.

CompressionLevel

Gets the Zstandard (1 to 22) or zlib (1 to 9) level, or 0 (the default) for the scheme's default: Zstandard DefaultLevel, zlib 6.

public int CompressionLevel { get; init; }

Property Value

int

Exceptions

ArgumentOutOfRangeException

The value is outside 0 to 22.

Cube

Gets whether SaveAll writes its rasters as cube maps, six faces a cube in the order +X, −X, +Y, −Y, +Z, −Z, rather than as a texture array. The rasters must then be square and a multiple of six. Defaults to false.

public bool Cube { get; init; }

Property Value

bool

Default

Gets the default options.

public static Ktx2WriterOptions Default { get; }

Property Value

Ktx2WriterOptions

Effort

Gets how hard the block encoders search, 0 (fastest) to 6 (best), on WebP's scale. Defaults to 4. The output is the same for any number of threads.

public int Effort { get; init; }

Property Value

int

Exceptions

ArgumentOutOfRangeException

The value is outside 0 to 6.

Format

Gets the format to write, or null (the default) for a KTX, KTX 2 or DDS source's own format when it is writable, else the uncompressed one nearest the raster's pixel type (Rgba8 for 8-bit colour, R8 for 8-bit gray, RgbaF16 for half floats and so on). A block format is chosen only from a texture source.

public KtxTextureFormat? Format { get; init; }

Property Value

KtxTextureFormat?

MipLevels

Gets how many mip levels to write: 0 (the default) for the full chain down to 1 × 1, 1 for mip 0 alone, or that many, at most the full chain. Mips average 2 × 2 blocks of premultiplied pixels (MipChain), in linear light for an sRGB format. An integer or depth format writes mip 0 alone unless a count is given, since averaging its values rarely means anything.

public int MipLevels { get; init; }

Property Value

int

Exceptions

ArgumentOutOfRangeException

The value is negative.

PremultipliedAlpha

Gets whether to write colour premultiplied by alpha, flagged so in the data format descriptor. Defaults to false.

public bool PremultipliedAlpha { get; init; }

Property Value

bool

Srgb

Gets whether to write the format's _SRGB form, or null (the default) to write it when the source texture was sRGB, or else when the raster is tagged sRGB. The 8-bit colour formats, BC1 to BC3, BC7, ETC1, ETC2, ASTC and the Basis formats have one; for the others the default falls back to UNORM, and true throws.

public bool? Srgb { get; init; }

Property Value

bool?

Supercompression

Gets the supercompression of each mip level: None (the default), Zstandard or Zlib. Etc1s always takes BasisLZ, which no other format can.

public KtxSupercompression Supercompression { get; init; }

Property Value

KtxSupercompression

UastcRdo

Gets the rate-distortion trade for Uastc: 0 (the default) leaves the blocks alone; higher values let blocks repeat bytes of their neighbours so Zstandard compresses them better, at a loss of quality. About 1 makes files a few per cent smaller, 16 about a third smaller and 3 to 4 dB lower.

public float UastcRdo { get; init; }

Property Value

float

Exceptions

ArgumentOutOfRangeException

The value is negative or not a number.

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