squish Namespace Reference

All squish API functions live in this namespace. More...

## Typedefs

typedef unsigned char | u8
| Typedef a quantity that is a single unsigned byte.

## Enumerations

enum | { kDxt1 = ( 1 << 0 ) , kDxt3 = ( 1 << 1 ) , kDxt5 = ( 1 << 2 ) , kBc4 = ( 1 << 3 ) , kBc5 = ( 1 << 4 ) , kColourClusterFit = ( 1 << 5 ) , kColourRangeFit = ( 1 << 6 ) , kWeightColourByAlpha = ( 1 << 7 ) , kColourIterativeClusterFit = ( 1 << 8 ) , kSourceBGRA = ( 1 << 9 ) }

## Functions

void | CompressMasked (u8 const *rgba, int mask, void *block, int flags, float *metric=0)
| Compresses a 4x4 block of pixels.
void | Compress (u8 const *rgba, void *block, int flags, float *metric=0)
| Compresses a 4x4 block of pixels.
void | Decompress (u8 *rgba, void const *block, int flags)
| Decompresses a 4x4 block of pixels.
int | GetStorageRequirements (int width, int height, int flags)
| Computes the amount of compressed storage required.
void | CompressImage (u8 const *rgba, int width, int height, int pitch, void *blocks, int flags, float *metric=0)
| Compresses an image in memory.
void | CompressImage (u8 const *rgba, int width, int height, void *blocks, int flags, float *metric=0)
void | DecompressImage (u8 *rgba, int width, int height, int pitch, void const *blocks, int flags)
| Decompresses an image in memory.
void | DecompressImage (u8 *rgba, int width, int height, void const *blocks, int flags)
void | ComputeMSE (u8 const *rgba, int width, int height, int pitch, u8 const *dxt, int flags, double &colourMSE, double &alphaMSE)
| Computes MSE of an compressed image in memory.
void | ComputeMSE (u8 const *rgba, int width, int height, u8 const *dxt, int flags, double &colourMSE, double &alphaMSE)

## Detailed Description

All squish API functions live in this namespace.

## Typedef Documentation

## u8

typedef unsigned char squish::u8

Typedef a quantity that is a single unsigned byte.

## Enumeration Type Documentation

## anonymous enum

anonymous enum

Enumerator
kDxt1 | Use DXT1 compression.
kDxt3 | Use DXT3 compression.
kDxt5 | Use DXT5 compression.
kBc4 | Use BC4 compression.
kBc5 | Use BC5 compression.
kColourClusterFit | Use a slow but high quality colour compressor (the default).
kColourRangeFit | Use a fast but low quality colour compressor.
kWeightColourByAlpha | Weight the colour by alpha during cluster fit (disabled by default).
kColourIterativeClusterFit | Use a very slow but very high quality colour compressor.
kSourceBGRA | Source is BGRA rather than RGBA.

## Function Documentation

## Compress()

void squish::Compress | ( | u8 const * | rgba,
|  | void * | block,
|  | int | flags,
|  | float * | metric = `0`
| ) |  |

inline

Compresses a 4x4 block of pixels.

Parameters

  rgba | The rgba values of the 16 source pixels.
  block | Storage for the compressed DXT block.
  flags | Compression flags.
  metric | An optional perceptual metric.

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 flags parameter should specify kDxt1, kDxt3, kDxt5, kBc4, or kBc5 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 to use when fitting the RGB components of the data. Possible colour compressors are: kColourClusterFit (the default), kColourRangeFit (very fast, low quality) or kColourIterativeClusterFit (slowest, best quality).

When using kColourClusterFit or kColourIterativeClusterFit, an additional flag can be specified to weight the importance of each pixel by its alpha value. For images that are rendered using alpha blending, this can significantly increase the perceived quality.

The metric parameter can be used to weight the relative importance of each colour channel, or pass NULL to use the default uniform weight of { 1.0f, 1.0f, 1.0f }. This replaces the previous flag-based control that allowed either uniform or "perceptual" weights with the fixed values { 0.2126f, 0.7152f, 0.0722f }. If non-NULL, the metric should point to a contiguous array of 3 floats.

This method is an inline that calls CompressMasked with a mask of 0xffff, provided for compatibility with older versions of squish.

References CompressMasked().

## CompressImage() [1/2]

void squish::CompressImage | ( | u8 const * | rgba,
|  | int | width,
|  | int | height,
|  | int | pitch,
|  | void * | blocks,
|  | int | flags,
|  | float * | metric = `0`
| ) |  |

Compresses an image in memory.

Parameters

  rgba | The pixels of the source.
  width | The width of the source image.
  height | The height of the source image.
  pitch | The pitch of the source image.
  blocks | Storage for the compressed output.
  flags | Compression flags.
  metric | An optional perceptual metric.

The source pixels should be presented as a contiguous array of width*height rgba values, with each component as 1 byte each. In memory this should be:

    { r1, g1, b1, a1, .... , rn, gn, bn, an } for n = width*height

The flags parameter should specify kDxt1, kDxt3, kDxt5, kBc4, or kBc5 compression, however, DXT1 will be used by default if none is specified. When using DXT1 compression, 8 bytes of storage are required for each compressed DXT block. DXT3 and DXT5 compression require 16 bytes of storage per block.

The flags parameter can also specify a preferred colour compressor to use when fitting the RGB components of the data. Possible colour compressors are: kColourClusterFit (the default), kColourRangeFit (very fast, low quality) or kColourIterativeClusterFit (slowest, best quality).

When using kColourClusterFit or kColourIterativeClusterFit, an additional flag can be specified to weight the importance of each pixel by its alpha value. For images that are rendered using alpha blending, this can significantly increase the perceived quality.

The metric parameter can be used to weight the relative importance of each colour channel, or pass NULL to use the default uniform weight of { 1.0f, 1.0f, 1.0f }. This replaces the previous flag-based control that allowed either uniform or "perceptual" weights with the fixed values { 0.2126f, 0.7152f, 0.0722f }. If non-NULL, the metric should point to a contiguous array of 3 floats.

Internally this function calls squish::CompressMasked for each block, which allows for pixels outside the image to take arbitrary values. The function squish::GetStorageRequirements can be called to compute the amount of memory to allocate for the compressed output.

Note on compression quality: When compressing textures with libsquish it is recommended to apply a gamma-correction beforehand. This will reduce the blockiness in dark areas. The level of necessary gamma-correction is platform dependent. For example, a gamma correction with gamma = 0.5 before compression and gamma = 2.0 after decompression yields good results on the Windows platform but for other platforms like MacOS X a different gamma value may be more suitable.

## CompressImage() [2/2]

void squish::CompressImage | ( | u8 const * | rgba,
|  | int | width,
|  | int | height,
|  | void * | blocks,
|  | int | flags,
|  | float * | metric = `0`
| ) |  |

## CompressMasked()

void squish::CompressMasked | ( | u8 const * | rgba,
|  | int | mask,
|  | void * | block,
|  | int | flags,
|  | float * | metric = `0`
| ) |  |

Compresses a 4x4 block of pixels.

Parameters

  rgba | The rgba values of the 16 source pixels.
  mask | The valid pixel mask.
  block | Storage for the compressed DXT block.
  flags | Compression flags.
  metric | An optional perceptual metric.

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 kDxt1, kDxt3, kDxt5, kBc4, or kBc5 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 to use when fitting the RGB components of the data. Possible colour compressors are: kColourClusterFit (the default), kColourRangeFit (very fast, low quality) or kColourIterativeClusterFit (slowest, best quality).

When using kColourClusterFit or kColourIterativeClusterFit, an additional flag can be specified to weight the importance of each pixel by its alpha value. For images that are rendered using alpha blending, this can significantly increase the perceived quality.

The metric parameter can be used to weight the relative importance of each colour channel, or pass NULL to use the default uniform weight of { 1.0f, 1.0f, 1.0f }. This replaces the previous flag-based control that allowed either uniform or "perceptual" weights with the fixed values { 0.2126f, 0.7152f, 0.0722f }. If non-NULL, the metric should point to a contiguous array of 3 floats.

Referenced by Compress().

## ComputeMSE() [1/2]

void squish::ComputeMSE | ( | u8 const * | rgba,
|  | int | width,
|  | int | height,
|  | int | pitch,
|  | u8 const * | dxt,
|  | int | flags,
|  | double & | colourMSE,
|  | double & | alphaMSE
| ) |  |

Computes MSE of an compressed image in memory.

Parameters

  rgba | The original image pixels.
  width | The width of the source image.
  height | The height of the source image.
  pitch | The pitch of the source image.
  dxt | The compressed dxt blocks
  flags | Compression flags.
  colourMSE | The MSE of the colour values.
  alphaMSE | The MSE of the alpha values.

The colour MSE and alpha MSE are computed across all pixels. The colour MSE is averaged across all rgb values (i.e. colourMSE = sum sum_k ||dxt.k - rgba.k||/3)

The flags parameter should specify kDxt1, kDxt3, kDxt5, kBc4, or kBc5 compression, however, DXT1 will be used by default if none is specified. All other flags are ignored.

Internally this function calls squish::Decompress for each block.

## ComputeMSE() [2/2]

void squish::ComputeMSE | ( | u8 const * | rgba,
|  | int | width,
|  | int | height,
|  | u8 const * | dxt,
|  | int | flags,
|  | double & | colourMSE,
|  | double & | alphaMSE
| ) |  |

## Decompress()

void squish::Decompress | ( | u8 * | rgba,
|  | void const * | block,
|  | int | flags
| ) |  |

Decompresses a 4x4 block of pixels.

Parameters

  rgba | Storage for the 16 decompressed pixels.
  block | The compressed DXT block.
  flags | Compression flags.

The decompressed pixels will be written as a contiguous array of 16 rgba values, with each component as 1 byte each. In memory this is:

    { r1, g1, b1, a1, .... , r16, g16, b16, a16 }

The flags parameter should specify kDxt1, kDxt3, kDxt5, kBc4, or kBc5 compression, however, DXT1 will be used by default if none is specified. All other flags are ignored.

## DecompressImage() [1/2]

void squish::DecompressImage | ( | u8 * | rgba,
|  | int | width,
|  | int | height,
|  | int | pitch,
|  | void const * | blocks,
|  | int | flags
| ) |  |

Decompresses an image in memory.

Parameters

  rgba | Storage for the decompressed pixels.
  width | The width of the source image.
  height | The height of the source image.
  pitch | The pitch of the decompressed pixels.
  blocks | The compressed DXT blocks.
  flags | Compression flags.

The decompressed pixels will be written as a contiguous array of width*height 16 rgba values, with each component as 1 byte each. In memory this is:

    { r1, g1, b1, a1, .... , rn, gn, bn, an } for n = width*height

The flags parameter should specify kDxt1, kDxt3, kDxt5, kBc4, or kBc5 compression, however, DXT1 will be used by default if none is specified. All other flags are ignored.

Internally this function calls squish::Decompress for each block.

## DecompressImage() [2/2]

void squish::DecompressImage | ( | u8 * | rgba,
|  | int | width,
|  | int | height,
|  | void const * | blocks,
|  | int | flags
| ) |  |

## GetStorageRequirements()

int squish::GetStorageRequirements | ( | int | width,
|  | int | height,
|  | int | flags
| ) |  |

Computes the amount of compressed storage required.

Parameters

  width | The width of the image.
  height | The height of the image.
  flags | Compression flags.

The flags parameter should specify kDxt1, kDxt3, kDxt5, kBc4, or kBc5 compression, however, DXT1 will be used by default if none is specified. All other flags are ignored.

Most DXT images will be a multiple of 4 in each dimension, but this function supports arbitrary size images by allowing the outer blocks to be only partially used.