/*
 * video fade filter
 * copyright (c) 2010 Brandon Mintern
 * based heavily on vf_negate.c which is copyright (c) 2007 Bobby Bingham
 *
 * 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
 */

/*
 # A few usage examples follow, usable too as test scenarios.

 # Fade in first 30 frames of video
 ffmpeg -i input.avi -vfilters fade=in:0:30 output.avi

 # Fade out last 45 frames of a 200-frame video
 ffmpeg -i input.avi -vfilters fade=out:155:45 output.avi

 # Fade in first 25 frames and fade out last 25 frames of a 1000-frame video
 ffmpeg -i input.avi -vfilters "fade=in:0:25, fade=out:975:25" output.avi

 # Make first 5 frames black, then fade in from frame 5-24
 ffmpeg -i input.avi -vfilters "fade=in:5:20" output.avi
*/

#include "avfilter.h"

typedef struct
{
    int fade_factor, fade_per_frame;
    unsigned int frame_index, start_frame, stop_frame;
    int hsub, vsub;
} FadeContext;

static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
{
    FadeContext *fade = ctx->priv;
    unsigned int frames;
    char in_out[4];

    if(args && sscanf(args, " %3[^:]:%u:%u", in_out,
                   &fade->start_frame, &frames) == 3) {
        frames = frames ? frames : 1;
        fade->fade_per_frame = (1 << 16) / frames;
        if (!strcmp(in_out, "in"))
            fade->fade_factor = 0;
        else if (!strcmp(in_out, "out")) {
            fade->fade_per_frame = -fade->fade_per_frame;
            fade->fade_factor = (1 << 16);
        }
        else {
            av_log(ctx, AV_LOG_ERROR,
                "init() 1st arg must be 'in' or 'out':'%s'\n", in_out);
            return -1;
        }
        fade->stop_frame = fade->start_frame + frames;
        return 0;
    }
    av_log(ctx, AV_LOG_ERROR,
           "init() expected 3 arguments '(in|out):#:#':'%s'\n", args);
    return -1;
}

static int query_formats(AVFilterContext *ctx)
{
    enum PixelFormat pix_fmts[] = {
        PIX_FMT_YUV444P,  PIX_FMT_YUV422P,  PIX_FMT_YUV420P,
        PIX_FMT_YUV411P,  PIX_FMT_YUV410P,
        PIX_FMT_YUVJ444P, PIX_FMT_YUVJ422P, PIX_FMT_YUVJ420P,
        PIX_FMT_YUV440P,  PIX_FMT_YUVJ440P,
        PIX_FMT_NONE
    };

    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
    return 0;
}

static int config_props(AVFilterLink *link)
{
    FadeContext *fade = link->dst->priv;
    avcodec_get_chroma_sub_sample(link->format, &fade->hsub, &fade->vsub);
    return 0;
}


static void start_frame(AVFilterLink *link, AVFilterPicRef *picref)
{
    FadeContext *fade = link->dst->priv;
    if(fade->frame_index >= fade->start_frame &&
       fade->frame_index < fade->stop_frame) {
        fade->fade_factor += fade->fade_per_frame;
    }
    fade->frame_index++;
    avfilter_default_start_frame(link, picref);
}

static void draw_slice(AVFilterLink *link, int y, int h, int slice_dir)
{
    FadeContext *fade = link->dst->priv;
    AVFilterPicRef *in  = link->cur_pic;
    AVFilterPicRef *out = link->dst->outputs[0]->outpic;
    uint8_t *inrow, *outrow;
    int i, j, plane;

    /* luma plane */
    inrow  = in-> data[0] + y * in-> linesize[0];
    outrow = out->data[0] + y * out->linesize[0];
    for(i = 0; i < h; i ++) {
        for(j = 0; j < link->w; j ++)
            /* fade->fade_factor is using 16 lower-order bits for decimal
             * places. 32768 = 1 << 15, it is an integer representation
             * of 0.5 and is for rounding. */
            outrow[j] = (uint8_t)((inrow[j]*fade->fade_factor+32768) >> 16);
        inrow  += in-> linesize[0];
        outrow += out->linesize[0];
    }

    /* chroma planes */
    for(plane = 1; plane < 3; plane ++) {
        inrow  = in-> data[plane] + (y >> fade->vsub) * in-> linesize[plane];
        outrow = out->data[plane] + (y >> fade->vsub) * out->linesize[plane];

        for(i = 0; i < h >> fade->vsub; i ++) {
            for(j = 0; j < link->w >> fade->hsub; j ++)
                /* 8421367 = ((128 << 1) + 1) << 15. It is an integer
                 * representation of 128.5. The .5 is for rounding
                 * purposes. */
                outrow[j] = (uint8_t)((8421367+(inrow[j]-128)*fade->fade_factor) >> 16);
            inrow  += in-> linesize[plane];
            outrow += out->linesize[plane];
        }
    }

    avfilter_draw_slice(link->dst->outputs[0], y, h, slice_dir);
}

AVFilter avfilter_vf_fade =
{
    .name      = "fade",

    .init      = init,

    .priv_size = sizeof(FadeContext),

    .query_formats = query_formats,

    .inputs    = (AVFilterPad[]) {{ .name            = "default",
                                    .type            = CODEC_TYPE_VIDEO,
                                    .start_frame     = start_frame,
                                    .draw_slice      = draw_slice,
                                    .config_props    = config_props,
                                    .min_perms       = AV_PERM_READ, },
                                  { .name = NULL}},
    .outputs   = (AVFilterPad[]) {{ .name            = "default",
                                    .type            = CODEC_TYPE_VIDEO, },
                                  { .name = NULL}},
};