/*
  * Copyright (c) 2010 Stefano Sabatini
  * Copyright (c) 2010 Baptiste Coudurier
  * 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
  */
 
 /**
  * @file
  * overlay one video on top of another
  */
 
 #include "avfilter.h"
 #include "libavutil/eval.h"
 #include "libavutil/avstring.h"
 #include "libavutil/pixdesc.h"

 #include "libavutil/imgutils.h"

 #include "internal.h"
 
 static const char *var_names[] = {
     "E",
     "PHI",
     "PI",
     "main_w",    "W", ///< width  of the main    video
     "main_h",    "H", ///< height of the main    video
     "overlay_w", "w", ///< width  of the overlay video
     "overlay_h", "h", ///< height of the overlay video
     NULL
 };
 
 enum var_name {
     VAR_E,
     VAR_PHI,
     VAR_PI,
     VAR_MAIN_W,    VAR_MW,
     VAR_MAIN_H,    VAR_MH,
     VAR_OVERLAY_W, VAR_OW,
     VAR_OVERLAY_H, VAR_OH,
     VAR_VARS_NB
 };
 
 #define MAIN    0
 #define OVERLAY 1
 
 typedef struct {
     int x, y;                   ///< position of overlayed picture
 
     AVFilterBufferRef *overpicref;
 
     int max_plane_step[4];      ///< steps per pixel for each plane
     int hsub, vsub;             ///< chroma subsampling values
 
     char x_expr[256], y_expr[256];
 } OverlayContext;
 
 static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
 {
     OverlayContext *over = ctx->priv;
 
     av_strlcpy(over->x_expr, "0", sizeof(over->x_expr));
     av_strlcpy(over->y_expr, "0", sizeof(over->y_expr));
 
     if (args)
         sscanf(args, "%255[^:]:%255[^:]", over->x_expr, over->y_expr);
 
     return 0;
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     OverlayContext *over = ctx->priv;
 
     if (over->overpicref)
         avfilter_unref_buffer(over->overpicref);
 }
 
 static int query_formats(AVFilterContext *ctx)
 {
     const enum PixelFormat inout_pix_fmts[] = { PIX_FMT_YUV420P,  PIX_FMT_NONE };
     const enum PixelFormat blend_pix_fmts[] = { PIX_FMT_YUVA420P, PIX_FMT_NONE };
     AVFilterFormats *inout_formats = avfilter_make_format_list(inout_pix_fmts);
     AVFilterFormats *blend_formats = avfilter_make_format_list(blend_pix_fmts);
 
     avfilter_formats_ref(inout_formats, &ctx->inputs [MAIN   ]->out_formats);
     avfilter_formats_ref(blend_formats, &ctx->inputs [OVERLAY]->out_formats);
     avfilter_formats_ref(inout_formats, &ctx->outputs[MAIN   ]->in_formats );
 
     return 0;
 }
 
 static int config_input_main(AVFilterLink *inlink)
 {
     OverlayContext *over = inlink->dst->priv;
     const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[inlink->format];
 
     av_image_fill_max_pixsteps(over->max_plane_step, NULL, pix_desc);
     over->hsub = pix_desc->log2_chroma_w;
     over->vsub = pix_desc->log2_chroma_h;
 
     return 0;
 }
 
 static int config_input_overlay(AVFilterLink *inlink)
 {
     AVFilterContext *ctx  = inlink->dst;
     OverlayContext  *over = inlink->dst->priv;
     char *expr;
     double var_values[VAR_VARS_NB], res;
     int ret;
 
     /* Finish the configuration by evaluating the expressions
        now when both inputs are configured. */
     var_values[VAR_E  ] = M_E;
     var_values[VAR_PHI] = M_PHI;
     var_values[VAR_PI ] = M_PI;
 
     var_values[VAR_MAIN_W   ] = var_values[VAR_MW] = ctx->inputs[MAIN   ]->w;
     var_values[VAR_MAIN_H   ] = var_values[VAR_MH] = ctx->inputs[MAIN   ]->h;
     var_values[VAR_OVERLAY_W] = var_values[VAR_OW] = ctx->inputs[OVERLAY]->w;
     var_values[VAR_OVERLAY_H] = var_values[VAR_OH] = ctx->inputs[OVERLAY]->h;
 
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->x_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
         goto fail;
     over->x = res;
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->y_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)))
         goto fail;
     over->y = res;
     /* x may depend on y */
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->x_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
         goto fail;
     over->x = res;
 
     av_log(ctx, AV_LOG_INFO,
            "main w:%d h:%d fmt:%s overlay x:%d y:%d w:%d h:%d fmt:%s\n",
            ctx->inputs[MAIN]->w, ctx->inputs[MAIN]->h,
            av_pix_fmt_descriptors[ctx->inputs[MAIN]->format].name,
            over->x, over->y,
            ctx->inputs[OVERLAY]->w, ctx->inputs[OVERLAY]->h,
            av_pix_fmt_descriptors[ctx->inputs[OVERLAY]->format].name);
 
     if (over->x < 0 || over->y < 0 ||
         over->x + var_values[VAR_OVERLAY_W] > var_values[VAR_MAIN_W] ||
         over->y + var_values[VAR_OVERLAY_H] > var_values[VAR_MAIN_H]) {
         av_log(ctx, AV_LOG_ERROR,
                "Overlay area (%d,%d)<->(%d,%d) not within the main area (0,0)<->(%d,%d) or zero-sized\n",
                over->x, over->y,
                (int)(over->x + var_values[VAR_OVERLAY_W]),
                (int)(over->y + var_values[VAR_OVERLAY_H]),
                (int)var_values[VAR_MAIN_W], (int)var_values[VAR_MAIN_H]);
         return AVERROR(EINVAL);
     }
     return 0;
 
 fail:
     av_log(NULL, AV_LOG_ERROR,
            "Error when evaluating the expression '%s'\n", expr);
     return ret;
 }
 
 static int config_output(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     int exact;
     // common timebase computation:
     AVRational tb1 = ctx->inputs[MAIN   ]->time_base;
     AVRational tb2 = ctx->inputs[OVERLAY]->time_base;
     AVRational *tb = &ctx->outputs[0]->time_base;
     exact = av_reduce(&tb->num, &tb->den,
                       av_gcd((int64_t)tb1.num * tb2.den,
                              (int64_t)tb2.num * tb1.den),
                       (int64_t)tb1.den * tb2.den, INT_MAX);
     av_log(ctx, AV_LOG_INFO,
            "main_tb:%d/%d overlay_tb:%d/%d -> tb:%d/%d exact:%d\n",
            tb1.num, tb1.den, tb2.num, tb2.den, tb->num, tb->den, exact);
     if (!exact)
         av_log(ctx, AV_LOG_WARNING,
                "Timestamp conversion inexact, timestamp information loss may occurr\n");
 
     outlink->w = ctx->inputs[MAIN]->w;
     outlink->h = ctx->inputs[MAIN]->h;
 
     return 0;
 }
 
 static AVFilterBufferRef *get_video_buffer(AVFilterLink *link, int perms, int w, int h)
 {
     return avfilter_get_video_buffer(link->dst->outputs[0], perms, w, h);
 }
 
 static void start_frame(AVFilterLink *inlink, AVFilterBufferRef *inpicref)
 {
     AVFilterBufferRef *outpicref = avfilter_ref_buffer(inpicref, ~0);
     AVFilterContext *ctx = inlink->dst;
     OverlayContext *over = ctx->priv;
 
     inlink->dst->outputs[0]->out_buf = outpicref;

     outpicref->pts = av_rescale_q(outpicref->pts, ctx->inputs[MAIN]->time_base,
                                   ctx->outputs[0]->time_base);

 
     if (!over->overpicref || over->overpicref->pts < outpicref->pts) {
         AVFilterBufferRef *old = over->overpicref;
         over->overpicref = NULL;
         avfilter_request_frame(ctx->inputs[OVERLAY]);
         if (over->overpicref) {
             if (old)
                 avfilter_unref_buffer(old);
         } else
             over->overpicref = old;
     }
 
     avfilter_start_frame(inlink->dst->outputs[0], outpicref);
 }
 
 static void start_frame_overlay(AVFilterLink *inlink, AVFilterBufferRef *inpicref)
 {
     AVFilterContext *ctx = inlink->dst;
     OverlayContext *over = ctx->priv;
 
     over->overpicref = inpicref;
     over->overpicref->pts = av_rescale_q(inpicref->pts, ctx->inputs[OVERLAY]->time_base,
                                          ctx->outputs[0]->time_base);
 }
 
 static void blend_slice(AVFilterContext *ctx,
                         AVFilterBufferRef *dst, AVFilterBufferRef *src,
                         int x, int y, int w, int h,
                         int slice_y, int slice_w, int slice_h)
 {
     OverlayContext *over = ctx->priv;
     int i, j, k;
     int width, height;
     int overlay_end_y = y+h;
     int slice_end_y = slice_y+slice_h;
     int end_y, start_y;
 
     width = FFMIN(slice_w - x, w);
     end_y = FFMIN(slice_end_y, overlay_end_y);
     start_y = FFMAX(y, slice_y);
     height = end_y - start_y;
 
     if (dst->format == PIX_FMT_BGR24 || dst->format == PIX_FMT_RGB24) {
         uint8_t *dp = dst->data[0] + x * 3 + start_y * dst->linesize[0];
         uint8_t *sp = src->data[0];
         int b = dst->format == PIX_FMT_BGR24 ? 2 : 0;
         int r = dst->format == PIX_FMT_BGR24 ? 0 : 2;
         if (slice_y > y)
             sp += (slice_y - y) * src->linesize[0];
         for (i = 0; i < height; i++) {
             uint8_t *d = dp, *s = sp;
             for (j = 0; j < width; j++) {
                 d[r] = (d[r] * (0xff - s[3]) + s[0] * s[3] + 128) >> 8;
                 d[1] = (d[1] * (0xff - s[3]) + s[1] * s[3] + 128) >> 8;
                 d[b] = (d[b] * (0xff - s[3]) + s[2] * s[3] + 128) >> 8;
                 d += 3;
                 s += 4;
             }
             dp += dst->linesize[0];
             sp += src->linesize[0];
         }
     } else {
         for (i = 0; i < 3; i++) {
             int hsub = i ? over->hsub : 0;
             int vsub = i ? over->vsub : 0;
             uint8_t *dp = dst->data[i] + (x >> hsub) +
                 (start_y >> vsub) * dst->linesize[i];
             uint8_t *sp = src->data[i];
             uint8_t *ap = src->data[3];
             int wp = FFALIGN(width, 1<<hsub) >> hsub;
             int hp = FFALIGN(height, 1<<vsub) >> vsub;
             if (slice_y > y) {
                 sp += ((slice_y - y) >> vsub) * src->linesize[i];
                 ap += (slice_y - y) * src->linesize[3];
             }
             for (j = 0; j < hp; j++) {
                 uint8_t *d = dp, *s = sp, *a = ap;
                 for (k = 0; k < wp; k++) {
                     // average alpha for color components, improve quality
                     int alpha_v, alpha_h, alpha;
                     if (hsub && vsub && j+1 < hp && k+1 < wp) {
                         alpha = (a[0] + a[src->linesize[3]] +
                                  a[1] + a[src->linesize[3]+1]) >> 2;
                     } else if (hsub || vsub) {
                         alpha_h = hsub && k+1 < wp ?
                             (a[0] + a[1]) >> 1 : a[0];
                         alpha_v = vsub && j+1 < hp ?
                             (a[0] + a[src->linesize[3]]) >> 1 : a[0];
                         alpha = (alpha_v + alpha_h) >> 1;
                     } else
                         alpha = a[0];
                     *d = (*d * (0xff - alpha) + *s++ * alpha + 128) >> 8;
                     d++;
                     a += 1 << hsub;
                 }
                 dp += dst->linesize[i];
                 sp += src->linesize[i];
                 ap += (1 << vsub) * src->linesize[3];
             }
         }
     }
 }
 
 static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
 {
     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = ctx->outputs[0];
     AVFilterBufferRef *outpicref = outlink->out_buf;
     OverlayContext *over = ctx->priv;
 
     if (over->overpicref &&
         !(over->x >= outpicref->video->w || over->y >= outpicref->video->h ||
           y+h < over->y || y >= over->y + over->overpicref->video->h)) {
         blend_slice(ctx, outpicref, over->overpicref, over->x, over->y,
                     over->overpicref->video->w, over->overpicref->video->h,
                     y, outpicref->video->w, h);
     }
     avfilter_draw_slice(outlink, y, h, slice_dir);
 }
 
 static void end_frame(AVFilterLink *inlink)
 {
     avfilter_end_frame(inlink->dst->outputs[0]);
     avfilter_unref_buffer(inlink->cur_buf);
 }
 
 static void null_draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir) { }
 
 static void null_end_frame(AVFilterLink *inlink) { }
 
 AVFilter avfilter_vf_overlay = {
     .name      = "overlay",
     .description = NULL_IF_CONFIG_SMALL("Overlay a video source on top of the input."),
 
     .init      = init,
     .uninit    = uninit,
 
     .priv_size = sizeof(OverlayContext),
 
     .query_formats = query_formats,
 
     .inputs    = (AVFilterPad[]) {{ .name            = "main",
                                     .type            = AVMEDIA_TYPE_VIDEO,
                                     .start_frame     = start_frame,
                                     .get_video_buffer= get_video_buffer,
                                     .config_props    = config_input_main,
                                     .draw_slice      = draw_slice,
                                     .end_frame       = end_frame,
                                     .min_perms       = AV_PERM_READ,
                                     .rej_perms       = AV_PERM_REUSE2|AV_PERM_PRESERVE, },
                                   { .name            = "overlay",
                                     .type            = AVMEDIA_TYPE_VIDEO,
                                     .start_frame     = start_frame_overlay,
                                     .config_props    = config_input_overlay,
                                     .draw_slice      = null_draw_slice,
                                     .end_frame       = null_end_frame,
                                     .min_perms       = AV_PERM_READ,
                                     .rej_perms       = AV_PERM_REUSE2, },
                                   { .name = NULL}},
     .outputs   = (AVFilterPad[]) {{ .name            = "default",
                                     .type            = AVMEDIA_TYPE_VIDEO,
                                     .config_props    = config_output, },
                                   { .name = NULL}},
 };