axmol/core/base/etc2.h

/****************************************************************************
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 Copyright (c) 2013-2016 Chukong Technologies Inc.
 Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.
 Copyright (c) 2020 C4games Ltd.

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/* The etc1/etc2 compression tools
 * https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-texture-compression-tool
 * https://github.com/google/etc2comp
 */

#ifndef __etc2_h__
#define __etc2_h__
/// @cond DO_NOT_SHOW

typedef unsigned char etc2_byte;
typedef int etc2_bool;
typedef unsigned int etc2_uint32;

#ifndef GL_COMPRESSED_RGB8_ETC2
#    define GL_COMPRESSED_RGB8_ETC2 0x9274
#endif

#ifndef GL_COMPRESSED_RGBA8_ETC2_EAC
#    define GL_COMPRESSED_RGBA8_ETC2_EAC 0x9278
#endif

// Size of a PKM header, in bytes.
#define ETC2_PKM_HEADER_SIZE 16

#define ETC2_RGB_NO_MIPMAPS 1
#define ETC2_RGBA_NO_MIPMAPS 3

// Check if a PKM header is correctly formatted.

etc2_bool etc2_pkm_is_valid(const etc2_byte* pHeader);

// Read the image width from a PKM header
etc2_uint32 etc2_pkm_get_width(const etc2_byte* pHeader);

// Read the image height from a PKM header
etc2_uint32 etc2_pkm_get_height(const etc2_byte* pHeader);

// Read the image format from a PKM header
etc2_uint32 etc2_pkm_get_format(const etc2_byte* pHeader);

/// <summary>
/// Decode ETC2_RGB/ETC2_RGBA to RGBA8888
/// Copy from:  https://github.com/google/angle/tree/master/src/image_util
/// </summary>
/// <param name="format">Must be ETC2_RGBA_NO_MIPMAPS or ETC2_RGB_NO_MIPMAPS</param>
/// <param name="input"></param>
/// <param name="output"></param>
/// <param name="width">pixelsHeight</param>
/// <param name="height">pixelsWidth</param>
/// <returns>0: success, -1: failed</returns>
int etc2_decode_image(int format, const etc2_byte* input, etc2_byte* output, etc2_uint32 width, etc2_uint32 height);

/// @endcond
#endif