//

// SPDX-License-Identifier: BSD-3-Clause

// Copyright (c) Contributors to the OpenEXR Project.

//

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

//

//  class B44Compressor

//

//  This compressor is lossy for HALF channels; the compression rate

//  is fixed at 32/14 (approximately 2.28).  FLOAT and UINT channels

//  are not compressed; their data are preserved exactly.

//

//  Each HALF channel is split into blocks of 4 by 4 pixels.  An

//  uncompressed block occupies 32 bytes, which are re-interpreted

//  as sixteen 16-bit unsigned integers, t[0] ... t[15].  Compression

//  shrinks the block to 14 bytes.  The compressed 14-byte block

//  contains

//

//   - t[0]

//

//   - a 6-bit shift value

//

//   - 15 densely packed 6-bit values, r[0] ... r[14], which are

//         computed by subtracting adjacent pixel values and right-

//     shifting the differences according to the stored shift value.

//

//     Differences between adjacent pixels are computed according

//     to the following diagram:

//

//     0 -------->  1 -------->  2 -------->  3

//               |     3            7           11

//               |

//               | 0

//               |

//               v

//     4 -------->  5 -------->  6 -------->  7

//               |     4            8           12

//               |

//               | 1

//               |

//               v

//     8 -------->  9 --------> 10 --------> 11

//               |     5            9           13

//               |

//               | 2

//               |

//               v

//    12 --------> 13 --------> 14 --------> 15

//                     6           10           14

//

//      Here

//

//               5 ---------> 6

//                     8

//

//      means that r[8] is the difference between t[5] and t[6].

//

//   - optionally, a 4-by-4 pixel block where all pixels have the

//     same value can be treated as a special case, where the

//     compressed block contains only 3 instead of 14 bytes:

//     t[0], followed by an "impossible" 6-bit shift value and

//     two padding bits.

//

//  This compressor can handle positive and negative pixel values.

//  NaNs and infinities are replaced with zeroes before compression.

//

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

#include "ImfB44Compressor.h"

OPENEXR_IMF_INTERNAL_NAMESPACE_SOURCE_ENTER

B44Compressor::B44Compressor (

    const Header& hdr,

    size_t        maxScanLineSize,

    int           numScanLines,

    bool          optFlatFields)

    : Compressor (hdr,

                  optFlatFields ? EXR_COMPRESSION_B44A : EXR_COMPRESSION_B44,

                  maxScanLineSize,

                  numScanLines)

{

}

B44Compressor::~B44Compressor ()

{

}

OPENEXR_IMF_INTERNAL_NAMESPACE_SOURCE_EXIT