vf_crop.c

Go to the documentation of this file.

/*
 * 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
 * video crop filter
 */

#include <stdio.h>

#include "avfilter.h"
#include "formats.h"
#include "internal.h"
#include "video.h"
#include "libavutil/eval.h"
#include "libavutil/avstring.h"
#include "libavutil/internal.h"
#include "libavutil/libm.h"
#include "libavutil/imgutils.h"
#include "libavutil/mathematics.h"
#include "libavutil/opt.h"

static const char *const var_names[] = {
    "in_w", "iw",   ///< width  of the input video
    "in_h", "ih",   ///< height of the input video
    "out_w", "ow",  ///< width  of the cropped video
    "out_h", "oh",  ///< height of the cropped video
    "a",
    "sar",
    "dar",
    "hsub",
    "vsub",
    "x",
    "y",
    "n",            ///< number of frame
    "pos",          ///< position in the file
    "t",            ///< timestamp expressed in seconds
    NULL
};

enum var_name {
    VAR_IN_W,  VAR_IW,
    VAR_IN_H,  VAR_IH,
    VAR_OUT_W, VAR_OW,
    VAR_OUT_H, VAR_OH,
    VAR_A,
    VAR_SAR,
    VAR_DAR,
    VAR_HSUB,
    VAR_VSUB,
    VAR_X,
    VAR_Y,
    VAR_N,
    VAR_POS,
    VAR_T,
    VAR_VARS_NB
};

typedef struct CropContext {
    const AVClass *class;
    int  x;             ///< x offset of the non-cropped area with respect to the input area
    int  y;             ///< y offset of the non-cropped area with respect to the input area
    int  w;             ///< width of the cropped area
    int  h;             ///< height of the cropped area

    AVRational out_sar; ///< output sample aspect ratio
    int keep_aspect;    ///< keep display aspect ratio when cropping
    int exact;          ///< exact cropping, for subsampled formats

    int max_step[4];    ///< max pixel step for each plane, expressed as a number of bytes
    int hsub, vsub;     ///< chroma subsampling
    char *x_expr, *y_expr, *w_expr, *h_expr;
    AVExpr *x_pexpr, *y_pexpr;  /* parsed expressions for x and y */
    double var_values[VAR_VARS_NB];
} CropContext;

static int query_formats(AVFilterContext *ctx)
{
    AVFilterFormats *formats = NULL;
    int fmt, ret;

    for (fmt = 0; av_pix_fmt_desc_get(fmt); fmt++) {
        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(fmt);
        if (!(desc->flags & (AV_PIX_FMT_FLAG_HWACCEL | AV_PIX_FMT_FLAG_BITSTREAM)) &&
            !((desc->log2_chroma_w || desc->log2_chroma_h) && !(desc->flags & AV_PIX_FMT_FLAG_PLANAR)) &&
            (ret = ff_add_format(&formats, fmt)) < 0)
            return ret;
    }

    return ff_set_common_formats(ctx, formats);
}

static av_cold void uninit(AVFilterContext *ctx)
{
    CropContext *s = ctx->priv;

    av_expr_free(s->x_pexpr);
    s->x_pexpr = NULL;
    av_expr_free(s->y_pexpr);
    s->y_pexpr = NULL;
}

static inline int normalize_double(int *n, double d)
{
    int ret = 0;

    if (isnan(d)) {
        ret = AVERROR(EINVAL);
    } else if (d > INT_MAX || d < INT_MIN) {
        *n = d > INT_MAX ? INT_MAX : INT_MIN;
        ret = AVERROR(EINVAL);
    } else
        *n = lrint(d);

    return ret;
}

static int config_input(AVFilterLink *link)
{
    AVFilterContext *ctx = link->dst;
    CropContext *s = ctx->priv;
    const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(link->format);
    int ret;
    const char *expr;
    double res;

    s->var_values[VAR_IN_W]  = s->var_values[VAR_IW] = ctx->inputs[0]->w;
    s->var_values[VAR_IN_H]  = s->var_values[VAR_IH] = ctx->inputs[0]->h;
    s->var_values[VAR_A]     = (float) link->w / link->h;
    s->var_values[VAR_SAR]   = link->sample_aspect_ratio.num ? av_q2d(link->sample_aspect_ratio) : 1;
    s->var_values[VAR_DAR]   = s->var_values[VAR_A] * s->var_values[VAR_SAR];
    s->var_values[VAR_HSUB]  = 1<<pix_desc->log2_chroma_w;
    s->var_values[VAR_VSUB]  = 1<<pix_desc->log2_chroma_h;
    s->var_values[VAR_X]     = NAN;
    s->var_values[VAR_Y]     = NAN;
    s->var_values[VAR_OUT_W] = s->var_values[VAR_OW] = NAN;
    s->var_values[VAR_OUT_H] = s->var_values[VAR_OH] = NAN;
    s->var_values[VAR_N]     = 0;
    s->var_values[VAR_T]     = NAN;
    s->var_values[VAR_POS]   = NAN;

    av_image_fill_max_pixsteps(s->max_step, NULL, pix_desc);
    s->hsub = pix_desc->log2_chroma_w;
    s->vsub = pix_desc->log2_chroma_h;

    if ((ret = av_expr_parse_and_eval(&res, (expr = s->w_expr),
                                      var_names, s->var_values,
                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
        goto fail_expr;
    s->var_values[VAR_OUT_W] = s->var_values[VAR_OW] = res;
    if ((ret = av_expr_parse_and_eval(&res, (expr = s->h_expr),
                                      var_names, s->var_values,
                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
        goto fail_expr;
    s->var_values[VAR_OUT_H] = s->var_values[VAR_OH] = res;
    /* evaluate again ow as it may depend on oh */
    if ((ret = av_expr_parse_and_eval(&res, (expr = s->w_expr),
                                      var_names, s->var_values,
                                      NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
        goto fail_expr;

    s->var_values[VAR_OUT_W] = s->var_values[VAR_OW] = res;
    if (normalize_double(&s->w, s->var_values[VAR_OUT_W]) < 0 ||
        normalize_double(&s->h, s->var_values[VAR_OUT_H]) < 0) {
        av_log(ctx, AV_LOG_ERROR,
               "Too big value or invalid expression for out_w/ow or out_h/oh. "
               "Maybe the expression for out_w:'%s' or for out_h:'%s' is self-referencing.\n",
               s->w_expr, s->h_expr);
        return AVERROR(EINVAL);
    }

    if (!s->exact) {
        s->w &= ~((1 << s->hsub) - 1);
        s->h &= ~((1 << s->vsub) - 1);
    }

    av_expr_free(s->x_pexpr);
    av_expr_free(s->y_pexpr);
    s->x_pexpr = s->y_pexpr = NULL;
    if ((ret = av_expr_parse(&s->x_pexpr, s->x_expr, var_names,
                             NULL, NULL, NULL, NULL, 0, ctx)) < 0 ||
        (ret = av_expr_parse(&s->y_pexpr, s->y_expr, var_names,
                             NULL, NULL, NULL, NULL, 0, ctx)) < 0)
        return AVERROR(EINVAL);

    if (s->keep_aspect) {
        AVRational dar = av_mul_q(link->sample_aspect_ratio,
                                  (AVRational){ link->w, link->h });
        av_reduce(&s->out_sar.num, &s->out_sar.den,
                  dar.num * s->h, dar.den * s->w, INT_MAX);
    } else
        s->out_sar = link->sample_aspect_ratio;

    av_log(ctx, AV_LOG_VERBOSE, "w:%d h:%d sar:%d/%d -> w:%d h:%d sar:%d/%d\n",
           link->w, link->h, link->sample_aspect_ratio.num, link->sample_aspect_ratio.den,
           s->w, s->h, s->out_sar.num, s->out_sar.den);

    if (s->w <= 0 || s->h <= 0 ||
        s->w > link->w || s->h > link->h) {
        av_log(ctx, AV_LOG_ERROR,
               "Invalid too big or non positive size for width '%d' or height '%d'\n",
               s->w, s->h);
        return AVERROR(EINVAL);
    }

    /* set default, required in the case the first computed value for x/y is NAN */
    s->x = (link->w - s->w) / 2;
    s->y = (link->h - s->h) / 2;
    if (!s->exact) {
        s->x &= ~((1 << s->hsub) - 1);
        s->y &= ~((1 << s->vsub) - 1);
    }
    return 0;

fail_expr:
    av_log(NULL, AV_LOG_ERROR, "Error when evaluating the expression '%s'\n", expr);
    return ret;
}

static int config_output(AVFilterLink *link)
{
    CropContext *s = link->src->priv;

    link->w = s->w;
    link->h = s->h;
    link->sample_aspect_ratio = s->out_sar;

    return 0;
}

static int filter_frame(AVFilterLink *link, AVFrame *frame)
{
    AVFilterContext *ctx = link->dst;
    CropContext *s = ctx->priv;
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
    int i;

    frame->width  = s->w;
    frame->height = s->h;

    s->var_values[VAR_N] = link->frame_count_out;
    s->var_values[VAR_T] = frame->pts == AV_NOPTS_VALUE ?
        NAN : frame->pts * av_q2d(link->time_base);
    s->var_values[VAR_POS] = av_frame_get_pkt_pos(frame) == -1 ?
        NAN : av_frame_get_pkt_pos(frame);
    s->var_values[VAR_X] = av_expr_eval(s->x_pexpr, s->var_values, NULL);
    s->var_values[VAR_Y] = av_expr_eval(s->y_pexpr, s->var_values, NULL);
    s->var_values[VAR_X] = av_expr_eval(s->x_pexpr, s->var_values, NULL);

    normalize_double(&s->x, s->var_values[VAR_X]);
    normalize_double(&s->y, s->var_values[VAR_Y]);

    if (s->x < 0)
        s->x = 0;
    if (s->y < 0)
        s->y = 0;
    if ((unsigned)s->x + (unsigned)s->w > link->w)
        s->x = link->w - s->w;
    if ((unsigned)s->y + (unsigned)s->h > link->h)
        s->y = link->h - s->h;
    if (!s->exact) {
        s->x &= ~((1 << s->hsub) - 1);
        s->y &= ~((1 << s->vsub) - 1);
    }

    av_log(ctx, AV_LOG_TRACE, "n:%d t:%f pos:%f x:%d y:%d x+w:%d y+h:%d\n",
            (int)s->var_values[VAR_N], s->var_values[VAR_T], s->var_values[VAR_POS],
            s->x, s->y, s->x+s->w, s->y+s->h);

    frame->data[0] += s->y * frame->linesize[0];
    frame->data[0] += s->x * s->max_step[0];

    if (!(desc->flags & AV_PIX_FMT_FLAG_PAL || desc->flags & AV_PIX_FMT_FLAG_PSEUDOPAL)) {
        for (i = 1; i < 3; i ++) {
            if (frame->data[i]) {
                frame->data[i] += (s->y >> s->vsub) * frame->linesize[i];
                frame->data[i] += (s->x * s->max_step[i]) >> s->hsub;
            }
        }
    }

    /* alpha plane */
    if (frame->data[3]) {
        frame->data[3] += s->y * frame->linesize[3];
        frame->data[3] += s->x * s->max_step[3];
    }

    return ff_filter_frame(link->dst->outputs[0], frame);
}

static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
                           char *res, int res_len, int flags)
{
    CropContext *s = ctx->priv;
    int ret;

    if (   !strcmp(cmd, "out_w")  || !strcmp(cmd, "w")
        || !strcmp(cmd, "out_h")  || !strcmp(cmd, "h")
        || !strcmp(cmd, "x")      || !strcmp(cmd, "y")) {

        int old_x = s->x;
        int old_y = s->y;
        int old_w = s->w;
        int old_h = s->h;

        AVFilterLink *outlink = ctx->outputs[0];
        AVFilterLink *inlink  = ctx->inputs[0];

        av_opt_set(s, cmd, args, 0);

        if ((ret = config_input(inlink)) < 0) {
            s->x = old_x;
            s->y = old_y;
            s->w = old_w;
            s->h = old_h;
            return ret;
        }

        ret = config_output(outlink);

    } else
        ret = AVERROR(ENOSYS);

    return ret;
}

#define OFFSET(x) offsetof(CropContext, x)
#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM

static const AVOption crop_options[] = {
    { "out_w",       "set the width crop area expression",   OFFSET(w_expr), AV_OPT_TYPE_STRING, {.str = "iw"}, CHAR_MIN, CHAR_MAX, FLAGS },
    { "w",           "set the width crop area expression",   OFFSET(w_expr), AV_OPT_TYPE_STRING, {.str = "iw"}, CHAR_MIN, CHAR_MAX, FLAGS },
    { "out_h",       "set the height crop area expression",  OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, CHAR_MIN, CHAR_MAX, FLAGS },
    { "h",           "set the height crop area expression",  OFFSET(h_expr), AV_OPT_TYPE_STRING, {.str = "ih"}, CHAR_MIN, CHAR_MAX, FLAGS },
    { "x",           "set the x crop area expression",       OFFSET(x_expr), AV_OPT_TYPE_STRING, {.str = "(in_w-out_w)/2"}, CHAR_MIN, CHAR_MAX, FLAGS },
    { "y",           "set the y crop area expression",       OFFSET(y_expr), AV_OPT_TYPE_STRING, {.str = "(in_h-out_h)/2"}, CHAR_MIN, CHAR_MAX, FLAGS },
    { "keep_aspect", "keep aspect ratio",                    OFFSET(keep_aspect), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },
    { "exact",       "do exact cropping",                    OFFSET(exact),  AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },
    { NULL }
};

AVFILTER_DEFINE_CLASS(crop);

static const AVFilterPad avfilter_vf_crop_inputs[] = {
    {
        .name         = "default",
        .type         = AVMEDIA_TYPE_VIDEO,
        .filter_frame = filter_frame,
        .config_props = config_input,
    },
    { NULL }
};

static const AVFilterPad avfilter_vf_crop_outputs[] = {
    {
        .name         = "default",
        .type         = AVMEDIA_TYPE_VIDEO,
        .config_props = config_output,
    },
    { NULL }
};

AVFilter ff_vf_crop = {
    .name            = "crop",
    .description     = NULL_IF_CONFIG_SMALL("Crop the input video."),
    .priv_size       = sizeof(CropContext),
    .priv_class      = &crop_class,
    .query_formats   = query_formats,
    .uninit          = uninit,
    .inputs          = avfilter_vf_crop_inputs,
    .outputs         = avfilter_vf_crop_outputs,
    .process_command = process_command,
};