include/astc-codec/astc-codec.h

// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef ASTC_CODEC_ASTC_CODEC_H_
#define ASTC_CODEC_ASTC_CODEC_H_

#include <cstddef>
#include <cstdint>

namespace astc_codec {

// These are the valid ASTC footprints according to the specification in
// Section C.2.7.
enum class FootprintType {
  k4x4,
  k5x4,
  k5x5,
  k6x5,
  k6x6,
  k8x5,
  k8x6,
  k10x5,
  k10x6,
  k8x8,
  k10x8,
  k10x10,
  k12x10,
  k12x12,

  kCount
};

// Decompresses ASTC LDR image data to a RGBA32 buffer.
//
// Supports formats defined in the KHR_texture_compression_astc_ldr spec and
// returns UNORM8 values.  sRGB is not supported, and should be implemented
// by the caller.
//
// |astc_data| - Compressed ASTC image buffer, must be at least |astc_data_size|
//               bytes long.
// |astc_data_size| - The size of |astc_data|, in bytes.
// |width| - Image width, in pixels.
// |height| - Image height, in pixels.
// |footprint| - The ASTC footprint (block size) of the compressed image buffer.
// |out_buffer| - Pointer to a buffer where the decompressed image will be
//                stored, must be at least |out_buffer_size| bytes long.
// |out_buffer_size| - The size of |out_buffer|, in bytes, at least
//                     height*out_buffer_stride. If this is too small, this
//                     function will return false and no data will be
//                     decompressed.
// |out_buffer_stride| - The stride that should be used to store rows of the
//                       decoded image, must be at least 4*width bytes.
//
// Returns true if the decompression succeeded, or false if decompression
// failed, or if the astc_data_size was too small for the given width, height,
// and footprint, or if out_buffer_size is too small.
bool ASTCDecompressToRGBA(const uint8_t* astc_data, size_t astc_data_size,
                          size_t width, size_t height, FootprintType footprint,
                          uint8_t* out_buffer, size_t out_buffer_size,
                          size_t out_buffer_stride);

}  // namespace astc_codec

#endif  // ASTC_CODEC_ASTC_CODEC_H_