

#ifndef SQUISH_H
#define SQUISH_H

//! All squish API functions live in this namespace.
namespace squish {

// -----------------------------------------------------------------------------

//! Typedef a quantity that is a single unsigned byte.
typedef unsigned char u8;

// -----------------------------------------------------------------------------

enum
{
    //! Use DXT1 compression.
    kDxt1 = ( 1 << 0 ),

    //! Use DXT3 compression.
    kDxt3 = ( 1 << 1 ),

    //! Use DXT5 compression.
    kDxt5 = ( 1 << 2 ),

    //! Use BC4 compression.
    kBc4 = ( 1 << 3 ),

    //! Use BC5 compression.
    kBc5 = ( 1 << 4 ),

    //! Use a slow but high quality colour compressor (the default).
    kColourClusterFit = ( 1 << 5 ),

    //! Use a fast but low quality colour compressor.
    kColourRangeFit = ( 1 << 6 ),

    //! Weight the colour by alpha during cluster fit (disabled by default).
    kWeightColourByAlpha = ( 1 << 7 ),

    //! Use a very slow but very high quality colour compressor.
    kColourIterativeClusterFit = ( 1 << 8 ),

    //! Source is BGRA rather than RGBA
    kSourceBGRA = ( 1 << 9 )
};

// -----------------------------------------------------------------------------

/*! @brief Compresses a 4x4 block of pixels.

    @param rgba   The rgba values of the 16 source pixels.
    @param mask   The valid pixel mask.
    @param block  Storage for the compressed DXT block.
    @param flags  Compression flags.
    @param 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.
*/
void CompressMasked( u8 const* rgba, int mask, void* block, int flags, float* metric = 0 );

// -----------------------------------------------------------------------------

/*! @brief Compresses a 4x4 block of pixels.

    @param rgba   The rgba values of the 16 source pixels.
    @param block  Storage for the compressed DXT block.
    @param flags  Compression flags.
    @param 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.
*/
inline void Compress( u8 const* rgba, void* block, int flags, float* metric = 0 )
{
    CompressMasked( rgba, 0xffff, block, flags, metric );
}

// -----------------------------------------------------------------------------

/*! @brief Decompresses a 4x4 block of pixels.

    @param rgba  Storage for the 16 decompressed pixels.
    @param block The compressed DXT block.
    @param 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.
*/
void Decompress( u8* rgba, void const* block, int flags );

// -----------------------------------------------------------------------------

/*! @brief Computes the amount of compressed storage required.

    @param width  The width of the image.
    @param height The height of the image.
    @param 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.
*/
int GetStorageRequirements( int width, int height, int flags );

// -----------------------------------------------------------------------------

/*! @brief Compresses an image in memory.

    @param rgba   The pixels of the source.
    @param width  The width of the source image.
    @param height The height of the source image.
    @param pitch  The pitch of the source image.
    @param blocks Storage for the compressed output.
    @param flags  Compression flags.
    @param 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.
*/
void CompressImage( u8 const* rgba, int width, int height, int pitch, void* blocks, int flags, float* metric = 0 );
void CompressImage( u8 const* rgba, int width, int height, void* blocks, int flags, float* metric = 0 );

// -----------------------------------------------------------------------------

/*! @brief Decompresses an image in memory.

    @param rgba   Storage for the decompressed pixels.
    @param width  The width of the source image.
    @param height The height of the source image.
    @param pitch  The pitch of the decompressed pixels.
    @param blocks The compressed DXT blocks.
    @param 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.
*/
void DecompressImage( u8* rgba, int width, int height, int pitch, void const* blocks, int flags );
void DecompressImage( u8* rgba, int width, int height, void const* blocks, int flags );

// -----------------------------------------------------------------------------

/*! @brief Computes MSE of an compressed image in memory.

    @param rgba      The original image pixels.
    @param width     The width of the source image.
    @param height    The height of the source image.
    @param pitch     The pitch of the source image.
    @param dxt       The compressed dxt blocks
    @param flags     Compression flags.
    @param colourMSE The MSE of the colour values.
    @param 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.
*/
void ComputeMSE(u8 const *rgba, int width, int height, int pitch, u8 const *dxt, int flags, double &colourMSE, double &alphaMSE);
void ComputeMSE(u8 const *rgba, int width, int height, u8 const *dxt, int flags, double &colourMSE, double &alphaMSE);

// -----------------------------------------------------------------------------

} // namespace squish

#endif // ndef SQUISH_H
