/*

 * FITS image encoder

 * Copyright (c) 2017 Paras Chadha

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * FITS image encoder

 *

 * Specification: https://fits.gsfc.nasa.gov/fits_standard.html Version 3.0

 *

 * RGBA images are encoded as planes in RGBA order. So, NAXIS3 is 3 or 4 for them.

 * Also CTYPE3 = 'RGB ' is added to the header to distinguish them from 3d images.

 */

#include "libavutil/intreadwrite.h"

#include "avcodec.h"

#include "bytestream.h"

#include "codec_internal.h"

#include "encode.h"

static int fits_encode_frame(AVCodecContext *avctx, AVPacket *pkt,

                             const AVFrame *p, int *got_packet)

{

    uint8_t *bytestream;

    const uint16_t flip = (1 << 15);

    uint64_t data_size = 0, padded_data_size = 0;

    int ret, bitpix, naxis3 = 1, i, j, k, bytes_left;

    int map[] = {2, 0, 1, 3}; // mapping from GBRA -> RGBA as RGBA is to be stored in FITS file..

    switch (avctx->pix_fmt) {

    case AV_PIX_FMT_GRAY8:

    case AV_PIX_FMT_GRAY16BE:

        map[0] = 0; // grayscale images should be directly mapped

        if (avctx->pix_fmt == AV_PIX_FMT_GRAY8) {

            bitpix = 8;

        } else {

            bitpix = 16;

        }

        break;

    case AV_PIX_FMT_GBRP:

    case AV_PIX_FMT_GBRAP:

        bitpix = 8;

        if (avctx->pix_fmt == AV_PIX_FMT_GBRP) {

            naxis3 = 3;

        } else {

            naxis3 = 4;

        }

        break;

    case AV_PIX_FMT_GBRP16BE:

    case AV_PIX_FMT_GBRAP16BE:

        bitpix = 16;

        if (avctx->pix_fmt == AV_PIX_FMT_GBRP16BE) {

            naxis3 = 3;

        } else {

            naxis3 = 4;

        }

        break;

    default:

        av_log(avctx, AV_LOG_ERROR, "unsupported pixel format\n");

        return AVERROR(EINVAL);

    }

    data_size = (bitpix >> 3) * avctx->height * avctx->width * naxis3;

    padded_data_size = ((data_size + 2879) / 2880 ) * 2880;

    if ((ret = ff_get_encode_buffer(avctx, pkt, padded_data_size, 0)) < 0)

        return ret;

    bytestream       = pkt->data;

    for (k = 0; k < naxis3; k++) {

        for (i = 0; i < avctx->height; i++) {

            const uint8_t *ptr = p->data[map[k]] + (avctx->height - i - 1) * p->linesize[map[k]];

            if (bitpix == 16) {

                for (j = 0; j < avctx->width; j++) {

                    // subtracting bzero is equivalent to first bit flip

                    bytestream_put_be16(&bytestream, AV_RB16(ptr) ^ flip);

                    ptr += 2;

                }

            } else {

                memcpy(bytestream, ptr, avctx->width);

                bytestream += avctx->width;

            }

        }

    }

    bytes_left = padded_data_size - data_size;

    memset(bytestream, 0, bytes_left);

    pkt->flags |= AV_PKT_FLAG_KEY;

    *got_packet = 1;

    return 0;

}

const FFCodec ff_fits_encoder = {

    .p.name         = "fits",

    CODEC_LONG_NAME("Flexible Image Transport System"),

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_FITS,

    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,

    FF_CODEC_ENCODE_CB(fits_encode_frame),

    CODEC_PIXFMTS(AV_PIX_FMT_GBRAP16BE, AV_PIX_FMT_GBRP16BE, AV_PIX_FMT_GBRP,

                  AV_PIX_FMT_GBRAP, AV_PIX_FMT_GRAY16BE, AV_PIX_FMT_GRAY8),

};