/*
  * Copyright (c) 2012 Steven Robertson
  *
  * 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
  * simple channel-swapping filter to get at the alpha component
  */
 
 #include <string.h>
 
 #include "libavutil/pixfmt.h"
 #include "avfilter.h"
 #include "drawutils.h"

 #include "internal.h"

 #include "formats.h"
 #include "video.h"
 
 enum { Y, U, V, A };
 
 typedef struct {
     int is_packed_rgb;
     uint8_t rgba_map[4];
 } AlphaExtractContext;
 
 static int query_formats(AVFilterContext *ctx)
 {

     static const enum AVPixelFormat in_fmts[] = {

         AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA420P,
         AV_PIX_FMT_RGBA, AV_PIX_FMT_BGRA, AV_PIX_FMT_ARGB, AV_PIX_FMT_ABGR,
         AV_PIX_FMT_NONE

     };

     static const enum AVPixelFormat out_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };

     ff_formats_ref(ff_make_format_list(in_fmts), &ctx->inputs[0]->out_formats);
     ff_formats_ref(ff_make_format_list(out_fmts), &ctx->outputs[0]->in_formats);
     return 0;
 }
 
 static int config_input(AVFilterLink *inlink)
 {
     AlphaExtractContext *extract = inlink->dst->priv;
     extract->is_packed_rgb =
         ff_fill_rgba_map(extract->rgba_map, inlink->format) >= 0;
     return 0;
 }
 

 static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *cur_buf)

 {
     AlphaExtractContext *extract = inlink->dst->priv;

     AVFilterLink *outlink = inlink->dst->outputs[0];
     AVFilterBufferRef *out_buf =
         ff_get_video_buffer(outlink, AV_PERM_WRITE, outlink->w, outlink->h);
     int ret;
 
     if (!out_buf) {
         ret = AVERROR(ENOMEM);
         goto end;
     }
     avfilter_copy_buffer_ref_props(out_buf, cur_buf);

 
     if (extract->is_packed_rgb) {
         int x, y;

         uint8_t *pcur, *pout;

         for (y = 0; y < outlink->h; y++) {

             pcur = cur_buf->data[0] + y * cur_buf->linesize[0] + extract->rgba_map[A];

             pout = out_buf->data[0] + y * out_buf->linesize[0];

             for (x = 0; x < outlink->w; x++) {

                 *pout = *pcur;

                 pout += 1;

                 pcur += 4;

             }
         }
     } else {

         const int linesize = abs(FFMIN(out_buf->linesize[Y], cur_buf->linesize[A]));

         int y;

         for (y = 0; y < outlink->h; y++) {

             memcpy(out_buf->data[Y] + y * out_buf->linesize[Y],
                    cur_buf->data[A] + y * cur_buf->linesize[A],
                    linesize);
         }
     }

 
     ret = ff_filter_frame(outlink, out_buf);
 
 end:
     avfilter_unref_buffer(cur_buf);
     return ret;

 }
 

 static const AVFilterPad alphaextract_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .config_props = config_input,

         .filter_frame = filter_frame,

         .min_perms    = AV_PERM_READ,
     },
     { NULL }
 };
 
 static const AVFilterPad alphaextract_outputs[] = {
     {
         .name = "default",
         .type = AVMEDIA_TYPE_VIDEO,
     },
     { NULL }
 };
 

 AVFilter avfilter_vf_alphaextract = {
     .name           = "alphaextract",
     .description    = NULL_IF_CONFIG_SMALL("Extract an alpha channel as a "
                       "grayscale image component."),
     .priv_size      = sizeof(AlphaExtractContext),
     .query_formats  = query_formats,

     .inputs         = alphaextract_inputs,
     .outputs        = alphaextract_outputs,

 };