crnlib.h

// File: crnlib.h - Advanced DXTn texture compression library.
// Copyright (c) 2010-2016 Richard Geldreich, Jr. and Binomial LLC
// See copyright notice and license at the end of this file.
//
// This header file contains the public crnlib declarations for DXTn,
// clustered DXTn, and CRN compression/decompression.
//
// Note: This library does NOT need to be linked into your game executable if
// all you want to do is transcode .CRN files to raw DXTn bits at run-time.
// The crn_decomp.h header file library contains all the code necessary for
// decompression.
//
// Important: If compiling with gcc, be sure strict aliasing is disabled: -fno-strict-aliasing
#ifndef CRNLIB_H
#define CRNLIB_H

#ifdef _MSC_VER
#pragma warning (disable: 4127) //  conditional expression is constant
#endif

#define CRNLIB_VERSION 104

#define CRNLIB_SUPPORT_ATI_COMPRESS 0
#define CRNLIB_SUPPORT_SQUISH 0

typedef unsigned char   crn_uint8;
typedef unsigned short  crn_uint16;
typedef unsigned int    crn_uint32;
typedef signed char     crn_int8;
typedef signed short    crn_int16;
typedef signed int      crn_int32;
typedef unsigned int    crn_bool;

// crnlib can compress to these file types.
enum crn_file_type
{
   // .CRN
   cCRNFileTypeCRN = 0,

   // .DDS using regular DXT or clustered DXT
   cCRNFileTypeDDS,

   cCRNFileTypeForceDWORD = 0xFFFFFFFF
};

// Supported compressed pixel formats.
// Basically all the standard DX9 formats, with some swizzled DXT5 formats
// (most of them supported by ATI's Compressonator), along with some ATI/X360 GPU specific formats.
enum crn_format
{
   cCRNFmtInvalid = -1,

   cCRNFmtDXT1 = 0,

   cCRNFmtFirstValid = cCRNFmtDXT1,

   // cCRNFmtDXT3 is not currently supported when writing to CRN - only DDS.
   cCRNFmtDXT3,

   cCRNFmtDXT5,

   // Various DXT5 derivatives
   cCRNFmtDXT5_CCxY,    // Luma-chroma
   cCRNFmtDXT5_xGxR,    // Swizzled 2-component
   cCRNFmtDXT5_xGBR,    // Swizzled 3-component
   cCRNFmtDXT5_AGBR,    // Swizzled 4-component

   // ATI 3DC and X360 DXN
   cCRNFmtDXN_XY,
   cCRNFmtDXN_YX,

   // DXT5 alpha blocks only
   cCRNFmtDXT5A,

   cCRNFmtETC1,

   cCRNFmtTotal,

   cCRNFmtForceDWORD = 0xFFFFFFFF
};

// Various library/file format limits.
enum crn_limits
{
   // Max. mipmap level resolution on any axis.
   cCRNMaxLevelResolution     = 4096,

   cCRNMinPaletteSize         = 8,
   cCRNMaxPaletteSize         = 8192,

   cCRNMaxFaces               = 6,
   cCRNMaxLevels              = 16,

   cCRNMaxHelperThreads       = 16,

   cCRNMinQualityLevel        = 0,
   cCRNMaxQualityLevel        = 255
};

// CRN/DDS compression flags.
// See the m_flags member in the crn_comp_params struct, below.
enum crn_comp_flags
{
   // Enables perceptual colorspace distance metrics if set.
   // Important: Be sure to disable this when compressing non-sRGB colorspace images, like normal maps!
   // Default: Set
   cCRNCompFlagPerceptual = 1,

   // Enables (up to) 8x8 macroblock usage if set. If disabled, only 4x4 blocks are allowed.
   // Compression ratio will be lower when disabled, but may cut down on blocky artifacts because the process used to determine
   // where large macroblocks can be used without artifacts isn't perfect.
   // Default: Set.
   cCRNCompFlagHierarchical = 2,

   // cCRNCompFlagQuick disables several output file optimizations - intended for things like quicker previews.
   // Default: Not set.
   cCRNCompFlagQuick = 4,

   // DXT1: OK to use DXT1 alpha blocks for better quality or DXT1A transparency.
   // DXT5: OK to use both DXT5 block types.
   // Currently only used when writing to .DDS files, as .CRN uses only a subset of the possible DXTn block types.
   // Default: Set.
   cCRNCompFlagUseBothBlockTypes = 8,

   // OK to use DXT1A transparent indices to encode black (assumes pixel shader ignores fetched alpha).
   // Currently only used when writing to .DDS files, .CRN never uses alpha blocks.
   // Default: Not set.
   cCRNCompFlagUseTransparentIndicesForBlack = 16,

   // Disables endpoint caching, for more deterministic output.
   // Currently only used when writing to .DDS files.
   // Default: Not set.
   cCRNCompFlagDisableEndpointCaching = 32,

   // If enabled, use the cCRNColorEndpointPaletteSize, etc. params to control the CRN palette sizes. Only useful when writing to .CRN files.
   // Default: Not set.
   cCRNCompFlagManualPaletteSizes = 64,

   // If enabled, DXT1A alpha blocks are used to encode single bit transparency.
   // Default: Not set.
   cCRNCompFlagDXT1AForTransparency = 128,

   // If enabled, the DXT1 compressor's color distance metric assumes the pixel shader will be converting the fetched RGB results to luma (Y part of YCbCr).
   // This increases quality when compressing grayscale images, because the compressor can spread the luma error amoung all three channels (i.e. it can generate blocks
   // with some chroma present if doing so will ultimately lead to lower luma error).
   // Only enable on grayscale source images.
   // Default: Not set.
   cCRNCompFlagGrayscaleSampling = 256,

   // If enabled, debug information will be output during compression.
   // Default: Not set.
   cCRNCompFlagDebugging = 0x80000000,

   cCRNCompFlagForceDWORD = 0xFFFFFFFF
};

// Controls DXTn quality vs. speed control - only used when compressing to .DDS.
enum crn_dxt_quality
{
   cCRNDXTQualitySuperFast,
   cCRNDXTQualityFast,
   cCRNDXTQualityNormal,
   cCRNDXTQualityBetter,
   cCRNDXTQualityUber,

   cCRNDXTQualityTotal,

   cCRNDXTQualityForceDWORD = 0xFFFFFFFF
};

// Which DXTn compressor to use when compressing to plain (non-clustered) .DDS.
enum crn_dxt_compressor_type
{
   cCRNDXTCompressorCRN,      // Use crnlib's ETC1 or DXTc block compressor (default, highest quality, comparable or better than ati_compress or squish, and crnlib's ETC1 is a lot fasterw with similiar quality to Erricson's)
   cCRNDXTCompressorCRNF,     // Use crnlib's "fast" DXTc block compressor
   cCRNDXTCompressorRYG,      // Use RYG's DXTc block compressor (low quality, but very fast)

#if CRNLIB_SUPPORT_ATI_COMPRESS
   cCRNDXTCompressorATI,
#endif

#if CRNLIB_SUPPORT_SQUISH
   cCRNDXTCompressorSquish,
#endif

   cCRNTotalDXTCompressors,

   cCRNDXTCompressorForceDWORD = 0xFFFFFFFF
};

// Progress callback function.
// Processing will stop prematurely (and fail) if the callback returns false.
// phase_index, total_phases - high level progress
// subphase_index, total_subphases - progress within current phase
typedef crn_bool (*crn_progress_callback_func)(crn_uint32 phase_index, crn_uint32 total_phases, crn_uint32 subphase_index, crn_uint32 total_subphases, void* pUser_data_ptr);

// CRN/DDS compression parameters struct.
struct crn_comp_params
{
   inline crn_comp_params() { clear(); }

   // Clear struct to default parameters.
   inline void clear()
   {
      m_size_of_obj = sizeof(*this);
      m_file_type = cCRNFileTypeCRN;
      m_faces = 1;
      m_width = 0;
      m_height = 0;
      m_levels = 1;
      m_format = cCRNFmtDXT1;
      m_flags = cCRNCompFlagPerceptual | cCRNCompFlagHierarchical | cCRNCompFlagUseBothBlockTypes;

      for (crn_uint32 f = 0; f < cCRNMaxFaces; f++)
         for (crn_uint32 l = 0; l < cCRNMaxLevels; l++)
            m_pImages[f][l] = NULL;

      m_target_bitrate = 0.0f;
      m_quality_level = cCRNMaxQualityLevel;
      m_dxt1a_alpha_threshold = 128;
      m_dxt_quality = cCRNDXTQualityUber;
      m_dxt_compressor_type = cCRNDXTCompressorCRN;
      m_alpha_component = 3;

      m_crn_adaptive_tile_color_psnr_derating = 2.0f;
      m_crn_adaptive_tile_alpha_psnr_derating = 2.0f;
      m_crn_color_endpoint_palette_size = 0;
      m_crn_color_selector_palette_size = 0;
      m_crn_alpha_endpoint_palette_size = 0;
      m_crn_alpha_selector_palette_size = 0;

      m_num_helper_threads = 0;
      m_userdata0 = 0;
      m_userdata1 = 0;
      m_pProgress_func = NULL;
      m_pProgress_func_data = NULL;
   }

   inline bool operator== (const crn_comp_params& rhs) const
   {
#define CRNLIB_COMP(x) do { if ((x) != (rhs.x)) return false; } while(0)
      CRNLIB_COMP(m_size_of_obj);
      CRNLIB_COMP(m_file_type);
      CRNLIB_COMP(m_faces);
      CRNLIB_COMP(m_width);
      CRNLIB_COMP(m_height);
      CRNLIB_COMP(m_levels);
      CRNLIB_COMP(m_format);
      CRNLIB_COMP(m_flags);
      CRNLIB_COMP(m_target_bitrate);
      CRNLIB_COMP(m_quality_level);
      CRNLIB_COMP(m_dxt1a_alpha_threshold);
      CRNLIB_COMP(m_dxt_quality);
      CRNLIB_COMP(m_dxt_compressor_type);
      CRNLIB_COMP(m_alpha_component);
      CRNLIB_COMP(m_crn_adaptive_tile_color_psnr_derating);
      CRNLIB_COMP(m_crn_adaptive_tile_alpha_psnr_derating);
      CRNLIB_COMP(m_crn_color_endpoint_palette_size);
      CRNLIB_COMP(m_crn_color_selector_palette_size);
      CRNLIB_COMP(m_crn_alpha_endpoint_palette_size);
      CRNLIB_COMP(m_crn_alpha_selector_palette_size);
      CRNLIB_COMP(m_num_helper_threads);
      CRNLIB_COMP(m_userdata0);
      CRNLIB_COMP(m_userdata1);
      CRNLIB_COMP(m_pProgress_func);
      CRNLIB_COMP(m_pProgress_func_data);

      for (crn_uint32 f = 0; f < cCRNMaxFaces; f++)
         for (crn_uint32 l = 0; l < cCRNMaxLevels; l++)
            CRNLIB_COMP(m_pImages[f][l]);

#undef CRNLIB_COMP
      return true;
   }

   // Returns true if the input parameters are reasonable.
   inline bool check() const
   {
      if ( (m_file_type > cCRNFileTypeDDS) ||
         (((int)m_quality_level < (int)cCRNMinQualityLevel) || ((int)m_quality_level > (int)cCRNMaxQualityLevel)) ||
         (m_dxt1a_alpha_threshold > 255) ||
         ((m_faces != 1) && (m_faces != 6)) ||
         ((m_width < 1) || (m_width > cCRNMaxLevelResolution)) ||
         ((m_height < 1) || (m_height > cCRNMaxLevelResolution)) ||
         ((m_levels < 1) || (m_levels > cCRNMaxLevels)) ||
         ((m_format < cCRNFmtDXT1) || (m_format >= cCRNFmtTotal)) ||
         ((m_crn_color_endpoint_palette_size) && ((m_crn_color_endpoint_palette_size < cCRNMinPaletteSize) || (m_crn_color_endpoint_palette_size > cCRNMaxPaletteSize))) ||
         ((m_crn_color_selector_palette_size) && ((m_crn_color_selector_palette_size < cCRNMinPaletteSize) || (m_crn_color_selector_palette_size > cCRNMaxPaletteSize))) ||
         ((m_crn_alpha_endpoint_palette_size) && ((m_crn_alpha_endpoint_palette_size < cCRNMinPaletteSize) || (m_crn_alpha_endpoint_palette_size > cCRNMaxPaletteSize))) ||
         ((m_crn_alpha_selector_palette_size) && ((m_crn_alpha_selector_palette_size < cCRNMinPaletteSize) || (m_crn_alpha_selector_palette_size > cCRNMaxPaletteSize))) ||
         (m_alpha_component > 3) ||
         (m_num_helper_threads > cCRNMaxHelperThreads) ||
         (m_dxt_quality > cCRNDXTQualityUber) ||
         (m_dxt_compressor_type >= cCRNTotalDXTCompressors) )
      {
         return false;
      }
      return true;
   }

   // Helper to set/get flags from m_flags member.
   inline bool get_flag(crn_comp_flags flag) const { return (m_flags & flag) != 0; }
   inline void set_flag(crn_comp_flags flag, bool val) { m_flags &= ~flag; if (val) m_flags |= flag; }

   crn_uint32                 m_size_of_obj;

   crn_file_type              m_file_type;               // Output file type: cCRNFileTypeCRN or cCRNFileTypeDDS.

   crn_uint32                 m_faces;                   // 1 (2D map) or 6 (cubemap)
   crn_uint32                 m_width;                   // [1,cCRNMaxLevelResolution], non-power of 2 OK, non-square OK
   crn_uint32                 m_height;                  // [1,cCRNMaxLevelResolution], non-power of 2 OK, non-square OK
   crn_uint32                 m_levels;                  // [1,cCRNMaxLevelResolution], non-power of 2 OK, non-square OK

   crn_format                 m_format;                  // Output pixel format.

   crn_uint32                 m_flags;                   // see crn_comp_flags enum

   // Array of pointers to 32bpp input images.
   const crn_uint32*          m_pImages[cCRNMaxFaces][cCRNMaxLevels];

   // Target bitrate - if non-zero, the compressor will use an interpolative search to find the
   // highest quality level that is <= the target bitrate. If it fails to find a bitrate high enough, it'll
   // try disabling adaptive block sizes (cCRNCompFlagHierarchical flag) and redo the search. This process can be pretty slow.
   float                      m_target_bitrate;

   // Desired quality level.
   // Currently, CRN and DDS quality levels are not compatible with eachother from an image quality standpoint.
   crn_uint32                 m_quality_level;           // [cCRNMinQualityLevel, cCRNMaxQualityLevel]

   // DXTn compression parameters.
   crn_uint32                 m_dxt1a_alpha_threshold;
   crn_dxt_quality            m_dxt_quality;
   crn_dxt_compressor_type    m_dxt_compressor_type;

   // Alpha channel's component. Defaults to 3.
   crn_uint32                 m_alpha_component;

   // Various low-level CRN specific parameters.
   float                      m_crn_adaptive_tile_color_psnr_derating;
   float                      m_crn_adaptive_tile_alpha_psnr_derating;

   crn_uint32                 m_crn_color_endpoint_palette_size;  // [cCRNMinPaletteSize,cCRNMaxPaletteSize]
   crn_uint32                 m_crn_color_selector_palette_size;  // [cCRNMinPaletteSize,cCRNMaxPaletteSize]

   crn_uint32                 m_crn_alpha_endpoint_palette_size;  // [cCRNMinPaletteSize,cCRNMaxPaletteSize]
   crn_uint32                 m_crn_alpha_selector_palette_size;  // [cCRNMinPaletteSize,cCRNMaxPaletteSize]

   // Number of helper threads to create during compression. 0=no threading.
   crn_uint32                 m_num_helper_threads;

   // CRN userdata0 and userdata1 members, which are written directly to the header of the output file.
   crn_uint32                 m_userdata0;
   crn_uint32                 m_userdata1;

   // User provided progress callback.
   crn_progress_callback_func m_pProgress_func;
   void*                      m_pProgress_func_data;
};

// Mipmap generator's mode.
enum crn_mip_mode
{
   cCRNMipModeUseSourceOrGenerateMips,       // Use source texture's mipmaps if it has any, otherwise generate new mipmaps
   cCRNMipModeUseSourceMips,                 // Use source texture's mipmaps if it has any, otherwise the output has no mipmaps
   cCRNMipModeGenerateMips,                  // Always generate new mipmaps
   cCRNMipModeNoMips,                        // Output texture has no mipmaps

   cCRNMipModeTotal,

   cCRNModeForceDWORD = 0xFFFFFFFF
};

const char* crn_get_mip_mode_desc(crn_mip_mode m);
const char* crn_get_mip_mode_name(crn_mip_mode m);

// Mipmap generator's filter kernel.
enum crn_mip_filter
{
   cCRNMipFilterBox,
   cCRNMipFilterTent,
   cCRNMipFilterLanczos4,
   cCRNMipFilterMitchell,
   cCRNMipFilterKaiser,                      // Kaiser=default mipmap filter

   cCRNMipFilterTotal,

   cCRNMipFilterForceDWORD = 0xFFFFFFFF
};

const char* crn_get_mip_filter_name(crn_mip_filter f);

// Mipmap generator's scale mode.
enum crn_scale_mode
{
   cCRNSMDisabled,
   cCRNSMAbsolute,
   cCRNSMRelative,
   cCRNSMLowerPow2,
   cCRNSMNearestPow2,
   cCRNSMNextPow2,

   cCRNSMTotal,

   cCRNSMForceDWORD = 0xFFFFFFFF
};

const char* crn_get_scale_mode_desc(crn_scale_mode sm);

// Mipmap generator parameters.
struct crn_mipmap_params
{
   inline crn_mipmap_params() { clear(); }

   inline void clear()
   {
      m_size_of_obj = sizeof(*this);
      m_mode = cCRNMipModeUseSourceOrGenerateMips;
      m_filter = cCRNMipFilterKaiser;
      m_gamma_filtering = true;
      m_gamma = 2.2f;
      // Default "blurriness" factor of .9 actually sharpens the output a little.
      m_blurriness = .9f;
      m_renormalize = false;
      m_tiled = false;
      m_max_levels = cCRNMaxLevels;
      m_min_mip_size = 1;

      m_scale_mode = cCRNSMDisabled;
      m_scale_x = 1.0f;
      m_scale_y = 1.0f;

      m_window_left = 0;
      m_window_top = 0;
      m_window_right = 0;
      m_window_bottom = 0;

      m_clamp_scale = false;
      m_clamp_width = 0;
      m_clamp_height = 0;
   }

   inline bool check() const { return true; }

   inline bool operator== (const crn_mipmap_params& rhs) const
   {
#define CRNLIB_COMP(x) do { if ((x) != (rhs.x)) return false; } while(0)
      CRNLIB_COMP(m_size_of_obj);
      CRNLIB_COMP(m_mode);
      CRNLIB_COMP(m_filter);
      CRNLIB_COMP(m_gamma_filtering);
      CRNLIB_COMP(m_gamma);
      CRNLIB_COMP(m_blurriness);
      CRNLIB_COMP(m_renormalize);
      CRNLIB_COMP(m_tiled);
      CRNLIB_COMP(m_max_levels);
      CRNLIB_COMP(m_min_mip_size);
      CRNLIB_COMP(m_scale_mode);
      CRNLIB_COMP(m_scale_x);
      CRNLIB_COMP(m_scale_y);
      CRNLIB_COMP(m_window_left);
      CRNLIB_COMP(m_window_top);
      CRNLIB_COMP(m_window_right);
      CRNLIB_COMP(m_window_bottom);
      CRNLIB_COMP(m_clamp_scale);
      CRNLIB_COMP(m_clamp_width);
      CRNLIB_COMP(m_clamp_height);
      return true;
#undef CRNLIB_COMP
   }
   crn_uint32     m_size_of_obj;

   crn_mip_mode   m_mode;
   crn_mip_filter m_filter;

   crn_bool       m_gamma_filtering;
   float          m_gamma;

   float          m_blurriness;

   crn_uint32     m_max_levels;
   crn_uint32     m_min_mip_size;

   crn_bool       m_renormalize;
   crn_bool       m_tiled;

   crn_scale_mode m_scale_mode;
   float          m_scale_x;
   float          m_scale_y;

   crn_uint32     m_window_left;
   crn_uint32     m_window_top;
   crn_uint32     m_window_right;
   crn_uint32     m_window_bottom;

   crn_bool       m_clamp_scale;
   crn_uint32     m_clamp_width;
   crn_uint32     m_clamp_height;
};

// -------- High-level helper function definitions for CDN/DDS compression.

#ifndef CRNLIB_MIN_ALLOC_ALIGNMENT
#define CRNLIB_MIN_ALLOC_ALIGNMENT sizeof(size_t) * 2
#endif

// Function to set an optional user provided memory allocation/reallocation/msize routines.
// By default, crnlib just uses malloc(), free(), etc. for all allocations.
typedef void*  (*crn_realloc_func)(void* p, size_t size, size_t* pActual_size, bool movable, void* pUser_data);
typedef size_t (*crn_msize_func)(void* p, void* pUser_data);
void crn_set_memory_callbacks(crn_realloc_func pRealloc, crn_msize_func pMSize, void* pUser_data);

// Frees memory blocks allocated by crn_compress(), crn_decompress_crn_to_dds(), or crn_decompress_dds_to_images().
void crn_free_block(void *pBlock);

// Compresses a 32-bit/pixel texture to either: a regular DX9 DDS file, a "clustered" (or reduced entropy) DX9 DDS file, or a CRN file in memory.
// Input parameters:
//  comp_params is the compression parameters struct, defined above.
//  compressed_size will be set to the size of the returned memory block containing the output file.
//  The returned block must be freed by calling crn_free_block().
//  *pActual_quality_level will be set to the actual quality level used to compress the image. May be NULL.
//  *pActual_bitrate will be set to the output file's effective bitrate, possibly taking into account LZMA compression. May be NULL.
// Return value:
//  The compressed file data, or NULL on failure.
//  compressed_size will be set to the size of the returned memory buffer.
// Notes:
//  A "regular" DDS file is compressed using normal DXTn compression at the specified DXT quality level.
//  A "clustered" DDS file is compressed using clustered DXTn compression to either the target bitrate or the specified integer quality factor.
//  The output file is a standard DX9 format DDS file, except the compressor assumes you will be later losslessly compressing the DDS output file using the LZMA algorithm.
//  A texture is defined as an array of 1 or 6 "faces" (6 faces=cubemap), where each "face" consists of between [1,cCRNMaxLevels] mipmap levels.
//  Mipmap levels are simple 32-bit 2D images with a pitch of width*sizeof(uint32), arranged in the usual raster order (top scanline first).
//  The image pixels may be grayscale (YYYX bytes in memory), grayscale/alpha (YYYA in memory), 24-bit (RGBX in memory), or 32-bit (RGBA) colors (where "X"=don't care).
//  RGB color data is generally assumed to be in the sRGB colorspace. If not, be sure to clear the "cCRNCompFlagPerceptual" in the crn_comp_params struct!
void *crn_compress(const crn_comp_params &comp_params, crn_uint32 &compressed_size, crn_uint32 *pActual_quality_level = NULL, float *pActual_bitrate = NULL);

// Like the above function, except this function can also do things like generate mipmaps, and resize or crop the input texture before compression.
// The actual operations performed are controlled by the crn_mipmap_params struct members.
// Be sure to set the "m_gamma_filtering" member of crn_mipmap_params to false if the input texture is not sRGB.
void *crn_compress(const crn_comp_params &comp_params, const crn_mipmap_params &mip_params, crn_uint32 &compressed_size, crn_uint32 *pActual_quality_level = NULL, float *pActual_bitrate = NULL);

// Transcodes an entire CRN file to DDS using the crn_decomp.h header file library to do most of the heavy lifting.
// The output DDS file's format is guaranteed to be one of the DXTn formats in the crn_format enum.
// This is a fast operation, because the CRN format is explicitly designed to be efficiently transcodable to DXTn.
// For more control over decompression, see the lower-level helper functions in crn_decomp.h, which do not depend at all on crnlib.
void *crn_decompress_crn_to_dds(const void *pCRN_file_data, crn_uint32 &file_size);

// Decompresses an entire DDS file in any supported format to uncompressed 32-bit/pixel image(s).
// See the crnlib::pixel_format enum in inc/dds_defs.h for a list of the supported DDS formats.
// You are responsible for freeing each image block, either by calling crn_free_all_images() or manually calling crn_free_block() on each image pointer.
struct crn_texture_desc
{
   crn_uint32 m_faces;
   crn_uint32 m_width;
   crn_uint32 m_height;
   crn_uint32 m_levels;
   crn_uint32 m_fmt_fourcc; // Same as crnlib::pixel_format
};
bool crn_decompress_dds_to_images(const void *pDDS_file_data, crn_uint32 dds_file_size, crn_uint32 **ppImages, crn_texture_desc &tex_desc);

// Frees all images allocated by crn_decompress_dds_to_images().
void crn_free_all_images(crn_uint32 **ppImages, const crn_texture_desc &desc);

// -------- crn_format related helpers functions.

// Returns the FOURCC format equivalent to the specified crn_format.
crn_uint32 crn_get_format_fourcc(crn_format fmt);

// Returns the crn_format's bits per texel.
crn_uint32 crn_get_format_bits_per_texel(crn_format fmt);

// Returns the crn_format's number of bytes per block.
crn_uint32 crn_get_bytes_per_dxt_block(crn_format fmt);

// Returns the non-swizzled, basic DXTn version of the specified crn_format.
// This is the format you would supply D3D or OpenGL.
crn_format crn_get_fundamental_dxt_format(crn_format fmt);

// -------- String helpers.

// Converts a crn_file_type to a string.
const char* crn_get_file_type_ext(crn_file_type file_type);

// Converts a crn_format to a string.
const char* crn_get_format_string(crn_format fmt);

// Converts a crn_dxt_quality to a string.
const char* crn_get_dxt_quality_string(crn_dxt_quality q);

// -------- Low-level DXTn 4x4 block compressor API

// crnlib's DXTn endpoint optimizer actually supports any number of source pixels (i.e. from 1 to thousands, not just 16),
// but for simplicity this API only supports 4x4 texel blocks.
typedef void *crn_block_compressor_context_t;

// Create a DXTn block compressor.
// This function only supports the basic/nonswizzled "fundamental" formats: DXT1, DXT3, DXT5, DXT5A, DXN_XY and DXN_YX.
// Avoid calling this multiple times if you intend on compressing many blocks, because it allocates some memory.
crn_block_compressor_context_t crn_create_block_compressor(const crn_comp_params &params);

// Compresses a block of 16 pixels to the destination DXTn block.
// pDst_block should be 8 (for DXT1/DXT5A) or 16 bytes (all the others).
// pPixels should be an array of 16 crn_uint32's. Each crn_uint32 must be r,g,b,a (r is always first) in memory.
void crn_compress_block(crn_block_compressor_context_t pContext, const crn_uint32 *pPixels, void *pDst_block);

// Frees a DXTn block compressor.
void crn_free_block_compressor(crn_block_compressor_context_t pContext);

// Unpacks a compressed block to pDst_pixels.
// pSrc_block should be 8 (for DXT1/DXT5A) or 16 bytes (all the others).
// pDst_pixel should be an array of 16 crn_uint32's. Each uint32 will be r,g,b,a (r is always first) in memory.
// crn_fmt should be one of the "fundamental" formats: DXT1, DXT3, DXT5, DXT5A, DXN_XY and DXN_YX.
// The various swizzled DXT5 formats (such as cCRNFmtDXT5_xGBR, etc.) will be unpacked as if they where plain DXT5.
// Returns false if the crn_fmt is invalid.
bool crn_decompress_block(const void *pSrc_block, crn_uint32 *pDst_pixels, crn_format crn_fmt);

#endif // CRNLIB_H

//------------------------------------------------------------------------------
//
// crnlib uses the ZLIB license:
// http://opensource.org/licenses/Zlib
//
// Copyright (c) 2010-2016 Richard Geldreich, Jr. and Binomial LLC
//
// This software is provided 'as-is', without any express or implied
// warranty.  In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software. If you use this software
// in a product, an acknowledgment in the product documentation would be
// appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not be
// misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source distribution.
//
//------------------------------------------------------------------------------