/*

 * Copyright (c) 2000 Fabrice Bellard

 * Copyright (c) 2002 Francois Revol

 * Copyright (c) 2006 Baptiste Coudurier

 * Copyright (c) 2018 Bjorn Roche

 * Copyright (c) 2018 Paul B Mahol

 *

 * first version by Francois Revol <revol@free.fr>

 *

 * 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

 * GIF encoder

 * @see http://www.w3.org/Graphics/GIF/spec-gif89a.txt

 */

#include "libavutil/attributes.h"

#include "libavutil/imgutils_internal.h"

#include "libavutil/mem.h"

#include "libavutil/opt.h"

#include "avcodec.h"

#include "bytestream.h"

#include "codec_internal.h"

#include "encode.h"

#include "lzw.h"

#include "gif.h"

#define DEFAULT_TRANSPARENCY_INDEX 0x1f

typedef struct GIFContext {

    const AVClass *class;

    LZWState *lzw;

    uint8_t *buf;

    uint8_t *shrunk_buf;

    int buf_size;

    AVFrame *last_frame;

    int flags;

    int image;

    int use_global_palette;

    uint32_t palette[AVPALETTE_COUNT];  ///< local reference palette for !pal8

    int palette_loaded;

    int transparent_index;

    uint8_t *tmpl;                      ///< temporary line buffer

} GIFContext;

enum {

    GF_OFFSETTING = 1<<0,

    GF_TRANSDIFF  = 1<<1,

};

static void shrink_palette(const uint32_t *src, uint8_t *map,

                           uint32_t *dst, size_t *palette_count)

{

    size_t colors_seen = 0;

    for (size_t i = 0; i < AVPALETTE_COUNT; i++) {

        int seen = 0;

        for (size_t c = 0; c < colors_seen; c++) {

            if (src[i] == dst[c]) {

                seen = 1;

                break;

            }

        }

        if (!seen) {

            dst[colors_seen] = src[i];

            map[i] = colors_seen;

            colors_seen++;

        }

    }

    *palette_count = colors_seen;

}

static void remap_frame_to_palette(const uint8_t *src, int src_linesize,

                                   uint8_t *dst, int dst_linesize,

                                   int w, int h, uint8_t *map)

{

    for (int i = 0; i < h; i++)

        for (int j = 0; j < w; j++)

            dst[i * dst_linesize + j] = map[src[i * src_linesize + j]];

}

static int is_image_translucent(AVCodecContext *avctx,

                                const uint8_t *buf, const int linesize)

{

    GIFContext *s = avctx->priv_data;

    int trans = s->transparent_index;

    if (trans < 0)

        return 0;

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

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

            if (buf[x] == trans) {

                return 1;

            }

        }

        buf += linesize;

    }

    return 0;

}

static int get_palette_transparency_index(const uint32_t *palette)

{

    int transparent_color_index = -1;

    unsigned i, smallest_alpha = 0xff;

    if (!palette)

        return -1;

    for (i = 0; i < AVPALETTE_COUNT; i++) {

        const uint32_t v = palette[i];

        if (v >> 24 < smallest_alpha) {

            smallest_alpha = v >> 24;

            transparent_color_index = i;

        }

    }

    return smallest_alpha < 128 ? transparent_color_index : -1;

}

static int pick_palette_entry(const uint8_t *buf, int linesize, int w, int h)

{

    int histogram[AVPALETTE_COUNT] = {0};

    int x, y, i;

    for (y = 0; y < h; y++) {

        for (x = 0; x < w; x++)

            histogram[buf[x]]++;

        buf += linesize;

    }

    for (i = 0; i < FF_ARRAY_ELEMS(histogram); i++)

        if (!histogram[i])

            return i;

    return -1;

}

static void gif_crop_translucent(AVCodecContext *avctx,

                                 const uint8_t *buf, const int linesize,

                                 int *width, int *height,

                                 int *x_start, int *y_start)

{

    GIFContext *s = avctx->priv_data;

    int trans = s->transparent_index;

    /* Crop image */

    if ((s->flags & GF_OFFSETTING) && trans >= 0) {

        const int w = avctx->width;

        const int h = avctx->height;

        int x_end = w - 1,

            y_end = h - 1;

        // crop top

        while (*y_start < y_end) {

            int is_trans = 1;

            for (int i = 0; i < w; i++) {

                if (buf[linesize * *y_start + i] != trans) {

                    is_trans = 0;

                    break;

                }

            }

            if (!is_trans)

                break;

            (*y_start)++;

        }

        // crop bottom

        while (y_end > *y_start) {

            int is_trans = 1;

            for (int i = 0; i < w; i++) {

                if (buf[linesize * y_end + i] != trans) {

                    is_trans = 0;

                    break;

                }

            }

            if (!is_trans)

                break;

            y_end--;

        }

        // crop left

        while (*x_start < x_end) {

            int is_trans = 1;

            for (int i = *y_start; i < y_end; i++) {

                if (buf[linesize * i + *x_start] != trans) {

                    is_trans = 0;

                    break;

                }

            }

            if (!is_trans)

                break;

            (*x_start)++;

        }

        // crop right

        while (x_end > *x_start) {

            int is_trans = 1;

            for (int i = *y_start; i < y_end; i++) {

                if (buf[linesize * i + x_end] != trans) {

                    is_trans = 0;

                    break;

                }

            }

            if (!is_trans)

                break;

            x_end--;

        }

        *height = y_end + 1 - *y_start;

        *width  = x_end + 1 - *x_start;

        av_log(avctx, AV_LOG_DEBUG,"%dx%d image at pos (%d;%d) [area:%dx%d]\n",

               *width, *height, *x_start, *y_start, avctx->width, avctx->height);

    }

}

static void gif_crop_opaque(AVCodecContext *avctx,

                            const uint32_t *palette,

                            const uint8_t *buf, const int linesize,

                            int *width, int *height, int *x_start, int *y_start)

{

    GIFContext *s = avctx->priv_data;

    /* Crop image */

    if ((s->flags & GF_OFFSETTING) && s->last_frame && !palette) {

        const uint8_t *ref = s->last_frame->data[0];

        const int ref_linesize = s->last_frame->linesize[0];

        int x_end = avctx->width  - 1,

            y_end = avctx->height - 1;

        /* skip common lines */

        while (*y_start < y_end) {

            if (memcmp(ref + *y_start*ref_linesize, buf + *y_start*linesize, *width))

                break;

            (*y_start)++;

        }

        while (y_end > *y_start) {

            if (memcmp(ref + y_end*ref_linesize, buf + y_end*linesize, *width))

                break;

            y_end--;

        }

        *height = y_end + 1 - *y_start;

        /* skip common columns */

        while (*x_start < x_end) {

            int same_column = 1;

            for (int y = *y_start; y <= y_end; y++) {

                if (ref[y*ref_linesize + *x_start] != buf[y*linesize + *x_start]) {

                    same_column = 0;

                    break;

                }

            }

            if (!same_column)

                break;

            (*x_start)++;

        }

        while (x_end > *x_start) {

            int same_column = 1;

            for (int y = *y_start; y <= y_end; y++) {

                if (ref[y*ref_linesize + x_end] != buf[y*linesize + x_end]) {

                    same_column = 0;

                    break;

                }

            }

            if (!same_column)

                break;

            x_end--;

        }

        *width = x_end + 1 - *x_start;

        av_log(avctx, AV_LOG_DEBUG,"%dx%d image at pos (%d;%d) [area:%dx%d]\n",

               *width, *height, *x_start, *y_start, avctx->width, avctx->height);

    }

}

static int gif_image_write_image(AVCodecContext *avctx,

                                 uint8_t **bytestream, uint8_t *end,

                                 const uint32_t *palette,

                                 const uint8_t *buf, const int linesize,

                                 AVPacket *pkt)

{

    GIFContext *s = avctx->priv_data;

    int disposal, len = 0, height = avctx->height, width = avctx->width, x, y;

    int x_start = 0, y_start = 0, trans = s->transparent_index;

    int bcid = -1, honor_transparency = (s->flags & GF_TRANSDIFF) && s->last_frame && !palette;

    const uint8_t *ptr;

    uint32_t shrunk_palette[AVPALETTE_COUNT];

    uint8_t map[AVPALETTE_COUNT] = { 0 };

    size_t shrunk_palette_count = 0;

    /*

     * We memset to 0xff instead of 0x00 so that the transparency detection

     * doesn't pick anything after the palette entries as the transparency

     * index, and because GIF89a requires us to always write a power-of-2

     * number of palette entries.

     */

    memset(shrunk_palette, 0xff, AVPALETTE_SIZE);

    if (!s->image && is_image_translucent(avctx, buf, linesize)) {

        gif_crop_translucent(avctx, buf, linesize, &width, &height, &x_start, &y_start);

        honor_transparency = 0;

        disposal = GCE_DISPOSAL_BACKGROUND;

    } else {

        gif_crop_opaque(avctx, palette, buf, linesize, &width, &height, &x_start, &y_start);

        disposal = GCE_DISPOSAL_INPLACE;

    }

    if (s->image || !avctx->frame_num) { /* GIF header */

        const uint32_t *global_palette = palette ? palette : s->palette;

        const AVRational sar = avctx->sample_aspect_ratio;

        int64_t aspect = 0;

        if (sar.num > 0 && sar.den > 0) {

            aspect = sar.num * 64LL / sar.den - 15;

            if (aspect < 0 || aspect > 255)

                aspect = 0;

        }

        bytestream_put_buffer(bytestream, gif89a_sig, sizeof(gif89a_sig));

        bytestream_put_le16(bytestream, avctx->width);

        bytestream_put_le16(bytestream, avctx->height);

        bcid = get_palette_transparency_index(global_palette);

        bytestream_put_byte(bytestream, ((uint8_t) s->use_global_palette << 7) | 0x70 | (s->use_global_palette ? 7 : 0)); /* flags: global clut, 256 entries */

        bytestream_put_byte(bytestream, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid); /* background color index */

        bytestream_put_byte(bytestream, aspect);

        if (s->use_global_palette) {

            for (int i = 0; i < 256; i++) {

                const uint32_t v = global_palette[i] & 0xffffff;

                bytestream_put_be24(bytestream, v);

            }

        }

    }

    if (honor_transparency && trans < 0) {

        trans = pick_palette_entry(buf + y_start*linesize + x_start,

                                   linesize, width, height);

        if (trans < 0) // TODO, patch welcome

            av_log(avctx, AV_LOG_DEBUG, "No available color, can not use transparency\n");

    }

    if (trans < 0)

        honor_transparency = 0;

    if (palette || !s->use_global_palette) {

        const uint32_t *pal = palette ? palette : s->palette;

        shrink_palette(pal, map, shrunk_palette, &shrunk_palette_count);

    }

    bcid = honor_transparency || disposal == GCE_DISPOSAL_BACKGROUND ? trans : get_palette_transparency_index(palette);

    /* graphic control extension */

    bytestream_put_byte(bytestream, GIF_EXTENSION_INTRODUCER);

    bytestream_put_byte(bytestream, GIF_GCE_EXT_LABEL);

    bytestream_put_byte(bytestream, 0x04); /* block size */

    bytestream_put_byte(bytestream, disposal<<2 | (bcid >= 0));

    bytestream_put_le16(bytestream, 5); // default delay

    bytestream_put_byte(bytestream, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : (shrunk_palette_count ? map[bcid] : bcid));

    bytestream_put_byte(bytestream, 0x00);

    /* image block */

    bytestream_put_byte(bytestream, GIF_IMAGE_SEPARATOR);

    bytestream_put_le16(bytestream, x_start);

    bytestream_put_le16(bytestream, y_start);

    bytestream_put_le16(bytestream, width);

    bytestream_put_le16(bytestream, height);

    if (palette || !s->use_global_palette) {

        unsigned pow2_count = av_log2(shrunk_palette_count - 1);

        unsigned i;

        bytestream_put_byte(bytestream, 1<<7 | pow2_count); /* flags */

        for (i = 0; i < 1 << (pow2_count + 1); i++) {

            const uint32_t v = shrunk_palette[i];

            bytestream_put_be24(bytestream, v);

        }

    } else {

        bytestream_put_byte(bytestream, 0x00); /* flags */

    }

    bytestream_put_byte(bytestream, 0x08);

    ff_lzw_encode_init(s->lzw, s->buf, s->buf_size,

                       12, FF_LZW_GIF, 1);

    if (shrunk_palette_count) {

        if (!s->shrunk_buf) {

            s->shrunk_buf = av_malloc(avctx->height * linesize);

            if (!s->shrunk_buf) {

                av_log(avctx, AV_LOG_ERROR, "Could not allocated remapped frame buffer.\n");

                return AVERROR(ENOMEM);

            }

        }

        remap_frame_to_palette(buf, linesize, s->shrunk_buf, linesize, avctx->width, avctx->height, map);

        ptr = s->shrunk_buf + y_start*linesize + x_start;

    } else {

        ptr = buf + y_start*linesize + x_start;

    }

    if (honor_transparency) {

        const int ref_linesize = s->last_frame->linesize[0];

        const uint8_t *ref = s->last_frame->data[0] + y_start*ref_linesize + x_start;

        for (y = 0; y < height; y++) {

            memcpy(s->tmpl, ptr, width);

            for (x = 0; x < width; x++)

                if (ref[x] == ptr[x])

                    s->tmpl[x] = trans;

            len += ff_lzw_encode(s->lzw, s->tmpl, width);

            ptr += linesize;

            ref += ref_linesize;

        }

    } else {

        for (y = 0; y < height; y++) {

            len += ff_lzw_encode(s->lzw, ptr, width);

            ptr += linesize;

        }

    }

    len += ff_lzw_encode_flush(s->lzw);

    ptr = s->buf;

    while (len > 0) {

        int size = FFMIN(255, len);

        bytestream_put_byte(bytestream, size);

        if (end - *bytestream < size)

            return -1;

        bytestream_put_buffer(bytestream, ptr, size);

        ptr += size;

        len -= size;

    }

    bytestream_put_byte(bytestream, 0x00); /* end of image block */

    return 0;

}

static av_cold int gif_encode_init(AVCodecContext *avctx)

{

    GIFContext *s = avctx->priv_data;

    if (avctx->width > 65535 || avctx->height > 65535) {

        av_log(avctx, AV_LOG_ERROR, "GIF does not support resolutions above 65535x65535\n");

        return AVERROR(EINVAL);

    }

    s->transparent_index = -1;

    s->lzw = av_mallocz(ff_lzw_encode_state_size);

    s->buf_size = avctx->width*avctx->height*2 + 1000;

    s->buf = av_malloc(s->buf_size);

    s->tmpl = av_malloc(avctx->width);

    if (!s->tmpl || !s->buf || !s->lzw)

        return AVERROR(ENOMEM);

    if (avpriv_set_systematic_pal2(s->palette, avctx->pix_fmt) < 0)

        av_assert0(avctx->pix_fmt == AV_PIX_FMT_PAL8);

    return 0;

}

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

                            const AVFrame *pict, int *got_packet)

{

    GIFContext *s = avctx->priv_data;

    uint8_t *outbuf_ptr, *end;

    const uint32_t *palette = NULL;

    int ret;

    if ((ret = ff_alloc_packet(avctx, pkt, avctx->width*avctx->height*7/5 + FF_INPUT_BUFFER_MIN_SIZE)) < 0)

        return ret;

    outbuf_ptr = pkt->data;

    end        = pkt->data + pkt->size;

    if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {

        palette = (uint32_t*)pict->data[1];

        if (!s->palette_loaded) {

            memcpy(s->palette, palette, AVPALETTE_SIZE);

            s->transparent_index = get_palette_transparency_index(palette);

            s->palette_loaded = 1;

            if (s->use_global_palette)

                palette = NULL;

        } else if (!memcmp(s->palette, palette, AVPALETTE_SIZE)) {

            palette = NULL;

        }

    }

    gif_image_write_image(avctx, &outbuf_ptr, end, palette,

                          pict->data[0], pict->linesize[0], pkt);

    if (!s->last_frame && !s->image) {

        s->last_frame = av_frame_alloc();

        if (!s->last_frame)

            return AVERROR(ENOMEM);

    }

    if (!s->image) {

        ret = av_frame_replace(s->last_frame, pict);

        if (ret < 0)

            return ret;

    }

    pkt->size   = outbuf_ptr - pkt->data;

    if (s->image || !avctx->frame_num)

        pkt->flags |= AV_PKT_FLAG_KEY;

    *got_packet = 1;

    return 0;

}

static av_cold int gif_encode_close(AVCodecContext *avctx)

{

    GIFContext *s = avctx->priv_data;

    av_freep(&s->lzw);

    av_freep(&s->buf);

    av_freep(&s->shrunk_buf);

    s->buf_size = 0;

    av_frame_free(&s->last_frame);

    av_freep(&s->tmpl);

    return 0;

}

#define OFFSET(x) offsetof(GIFContext, x)

#define FLAGS AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_ENCODING_PARAM

static const AVOption gif_options[] = {

    { "gifflags", "set GIF flags", OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = GF_OFFSETTING|GF_TRANSDIFF}, 0, INT_MAX, FLAGS, .unit = "flags" },

        { "offsetting", "enable picture offsetting", 0, AV_OPT_TYPE_CONST, {.i64=GF_OFFSETTING}, INT_MIN, INT_MAX, FLAGS, .unit = "flags" },

        { "transdiff", "enable transparency detection between frames", 0, AV_OPT_TYPE_CONST, {.i64=GF_TRANSDIFF}, INT_MIN, INT_MAX, FLAGS, .unit = "flags" },

    { "gifimage", "enable encoding only images per frame", OFFSET(image), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },

    { "global_palette", "write a palette to the global gif header where feasible", OFFSET(use_global_palette), AV_OPT_TYPE_BOOL, {.i64=1}, 0, 1, FLAGS },

    { NULL }

};

static const AVClass gif_class = {

    .class_name = "GIF encoder",

    .item_name  = av_default_item_name,

    .option     = gif_options,

    .version    = LIBAVUTIL_VERSION_INT,

};

const FFCodec ff_gif_encoder = {

    .p.name         = "gif",

    CODEC_LONG_NAME("GIF (Graphics Interchange Format)"),

    .p.type         = AVMEDIA_TYPE_VIDEO,

    .p.id           = AV_CODEC_ID_GIF,

    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,

    .priv_data_size = sizeof(GIFContext),

    .init           = gif_encode_init,

    FF_CODEC_ENCODE_CB(gif_encode_frame),

    .close          = gif_encode_close,

    CODEC_PIXFMTS(AV_PIX_FMT_RGB8, AV_PIX_FMT_BGR8, AV_PIX_FMT_RGB4_BYTE,

                  AV_PIX_FMT_BGR4_BYTE, AV_PIX_FMT_GRAY8, AV_PIX_FMT_PAL8),

    .p.priv_class   = &gif_class,

    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP,

};