PeerStreamer

/*

 * Copyright (c) 2011 Stefano Sabatini

 * Copyright (c) 2010 S.N. Hemanth Meenakshisundaram

 * Copyright (c) 2003 Gustavo Sverzut Barbieri <gsbarbieri@yahoo.com.br>

 *

 * 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

 * drawtext filter, based on the original FFmpeg vhook/drawtext.c

 * filter by Gustavo Sverzut Barbieri

 */

#include <sys/time.h>

#include <time.h>

#include "libavutil/colorspace.h"

#include "libavutil/file.h"

#include "libavutil/opt.h"

#include "libavutil/parseutils.h"

#include "libavutil/pixdesc.h"

#include "libavutil/tree.h"

#include "avfilter.h"

#include "drawutils.h"

#undef time

#include <ft2build.h>

#include <freetype/config/ftheader.h>

#include FT_FREETYPE_H

#include FT_GLYPH_H

#define MAX_EXPANDED_TEXT_SIZE 2048

typedef struct {

    const AVClass *class;

    char *fontfile;                 ///< font to be used

    char *text;                     ///< text to be drawn

    int ft_load_flags;              ///< flags used for loading fonts, see FT_LOAD_*

    /** buffer containing the text expanded by strftime */

    char expanded_text[MAX_EXPANDED_TEXT_SIZE];

    /** positions for each element in the text */

    FT_Vector positions[MAX_EXPANDED_TEXT_SIZE];

    char *textfile;                 ///< file with text to be drawn

    unsigned int x;                 ///< x position to start drawing text

    unsigned int y;                 ///< y position to start drawing text

    unsigned int fontsize;          ///< font size to use

    char *fontcolor_string;         ///< font color as string

    char *boxcolor_string;          ///< box color as string

    uint8_t fontcolor[4];           ///< foreground color

    uint8_t boxcolor[4];            ///< background color

    uint8_t fontcolor_rgba[4];      ///< foreground color in RGBA

    uint8_t boxcolor_rgba[4];       ///< background color in RGBA

    short int draw_box;             ///< draw box around text - true or false

    int use_kerning;                ///< font kerning is used - true/false

    int tabsize;                    ///< tab size

    FT_Library library;             ///< freetype font library handle

    FT_Face face;                   ///< freetype font face handle

    struct AVTreeNode *glyphs;      ///< rendered glyphs, stored using the UTF-32 char code

    int hsub, vsub;                 ///< chroma subsampling values

    int is_packed_rgb;

    int pixel_step[4];              ///< distance in bytes between the component of each pixel

    uint8_t rgba_map[4];            ///< map RGBA offsets to the positions in the packed RGBA format

    uint8_t *box_line[4];           ///< line used for filling the box background

} DrawTextContext;

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

static const AVOption drawtext_options[]= {

{"fontfile", "set font file",        OFFSET(fontfile),         FF_OPT_TYPE_STRING, 0,  CHAR_MIN, CHAR_MAX },

{"text",     "set text",             OFFSET(text),             FF_OPT_TYPE_STRING, 0,  CHAR_MIN, CHAR_MAX },

{"textfile", "set text file",        OFFSET(textfile),         FF_OPT_TYPE_STRING, 0,  CHAR_MIN, CHAR_MAX },

{"fontcolor","set foreground color", OFFSET(fontcolor_string), FF_OPT_TYPE_STRING, 0,  CHAR_MIN, CHAR_MAX },

{"boxcolor", "set box color",        OFFSET(boxcolor_string),  FF_OPT_TYPE_STRING, 0,  CHAR_MIN, CHAR_MAX },

{"box",      "set box",              OFFSET(draw_box),         FF_OPT_TYPE_INT,    0,         0,        1 },

{"fontsize", "set font size",        OFFSET(fontsize),         FF_OPT_TYPE_INT,   16,         1,       72 },

{"x",        "set x",                OFFSET(x),                FF_OPT_TYPE_INT,    0,         0,  INT_MAX },

{"y",        "set y",                OFFSET(y),                FF_OPT_TYPE_INT,    0,         0,  INT_MAX },

{"tabsize",  "set tab size",         OFFSET(tabsize),          FF_OPT_TYPE_INT,    4,         0,  INT_MAX },

/* FT_LOAD_* flags */

{"ft_load_flags", "set font loading flags for libfreetype",   OFFSET(ft_load_flags),  FF_OPT_TYPE_FLAGS,  FT_LOAD_DEFAULT|FT_LOAD_RENDER, 0, INT_MAX, 0, "ft_load_flags" },

{"default",                     "set default",                     0, FF_OPT_TYPE_CONST, FT_LOAD_DEFAULT,                     INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"no_scale",                    "set no_scale",                    0, FF_OPT_TYPE_CONST, FT_LOAD_NO_SCALE,                    INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"no_hinting",                  "set no_hinting",                  0, FF_OPT_TYPE_CONST, FT_LOAD_NO_HINTING,                  INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"render",                      "set render",                      0, FF_OPT_TYPE_CONST, FT_LOAD_RENDER,                      INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"no_bitmap",                   "set no_bitmap",                   0, FF_OPT_TYPE_CONST, FT_LOAD_NO_BITMAP,                   INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"vertical_layout",             "set vertical_layout",             0, FF_OPT_TYPE_CONST, FT_LOAD_VERTICAL_LAYOUT,             INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"force_autohint",              "set force_autohint",              0, FF_OPT_TYPE_CONST, FT_LOAD_FORCE_AUTOHINT,              INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"crop_bitmap",                 "set crop_bitmap",                 0, FF_OPT_TYPE_CONST, FT_LOAD_CROP_BITMAP,                 INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"pedantic",                    "set pedantic",                    0, FF_OPT_TYPE_CONST, FT_LOAD_PEDANTIC,                    INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"ignore_global_advance_width", "set ignore_global_advance_width", 0, FF_OPT_TYPE_CONST, FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH, INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"no_recurse",                  "set no_recurse",                  0, FF_OPT_TYPE_CONST, FT_LOAD_NO_RECURSE,                  INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"ignore_transform",            "set ignore_transform",            0, FF_OPT_TYPE_CONST, FT_LOAD_IGNORE_TRANSFORM,            INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"monochrome",                  "set monochrome",                  0, FF_OPT_TYPE_CONST, FT_LOAD_MONOCHROME,                  INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"linear_design",               "set linear_design",               0, FF_OPT_TYPE_CONST, FT_LOAD_LINEAR_DESIGN,               INT_MIN, INT_MAX, 0, "ft_load_flags" },

{"no_autohint",                 "set no_autohint",                 0, FF_OPT_TYPE_CONST, FT_LOAD_NO_AUTOHINT,                 INT_MIN, INT_MAX, 0, "ft_load_flags" },

{NULL},

};

static const char *drawtext_get_name(void *ctx)

{

    return "drawtext";

}

static const AVClass drawtext_class = {

    "DrawTextContext",

    drawtext_get_name,

    drawtext_options

};

#undef __FTERRORS_H__

#define FT_ERROR_START_LIST {

#define FT_ERRORDEF(e, v, s) { (e), (s) },

#define FT_ERROR_END_LIST { 0, NULL } };

struct ft_error

{

    int err;

    const char *err_msg;

} static ft_errors[] =

#include FT_ERRORS_H

#define FT_ERRMSG(e) ft_errors[e].err_msg

typedef struct {

    FT_Glyph *glyph;

    uint32_t code;

    FT_Bitmap bitmap; ///< array holding bitmaps of font

    FT_BBox bbox;

    int advance;

    int bitmap_left;

    int bitmap_top;

} Glyph;

static int glyph_cmp(const Glyph *a, const Glyph *b)

{

    int64_t diff = (int64_t)a->code - (int64_t)b->code;

    return diff > 0 ? 1 : diff < 0 ? -1 : 0;

}

/**

 * Load glyphs corresponding to the UTF-32 codepoint code.

 */

static int load_glyph(AVFilterContext *ctx, Glyph **glyph_ptr, uint32_t code)

{

    DrawTextContext *dtext = ctx->priv;

    Glyph *glyph = av_mallocz(sizeof(Glyph));

    struct AVTreeNode *node = NULL;

    int ret;

    /* load glyph into dtext->face->glyph */

    ret = FT_Load_Char(dtext->face, code, dtext->ft_load_flags);

    if (ret)

        return AVERROR(EINVAL);

    /* save glyph */

    glyph->code  = code;

    glyph->glyph = av_mallocz(sizeof(FT_Glyph));

    ret = FT_Get_Glyph(dtext->face->glyph, glyph->glyph);

    if (ret)

        return AVERROR(EINVAL);

    glyph->bitmap      = dtext->face->glyph->bitmap;

    glyph->bitmap_left = dtext->face->glyph->bitmap_left;

    glyph->bitmap_top  = dtext->face->glyph->bitmap_top;

    glyph->advance     = dtext->face->glyph->advance.x >> 6;

    /* measure text height to calculate text_height (or the maximum text height) */

    FT_Glyph_Get_CBox(*glyph->glyph, ft_glyph_bbox_pixels, &glyph->bbox);

    /* cache the newly created glyph */

    if (!node)

        node = av_mallocz(av_tree_node_size);

    av_tree_insert(&dtext->glyphs, glyph, (void *)glyph_cmp, &node);

    if (glyph_ptr)

        *glyph_ptr = glyph;

    return 0;

}

static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)

{

    int err;

    DrawTextContext *dtext = ctx->priv;

    dtext->class = &drawtext_class;

    av_opt_set_defaults2(dtext, 0, 0);

    dtext->fontcolor_string = av_strdup("black");

    dtext->boxcolor_string = av_strdup("white");

    if ((err = (av_set_options_string(dtext, args, "=", ":"))) < 0) {

        av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);

        return err;

    }

    if (!dtext->fontfile) {

        av_log(ctx, AV_LOG_ERROR, "No font filename provided\n");

        return AVERROR(EINVAL);

    }

    if (dtext->textfile) {

        uint8_t *textbuf;

        size_t textbuf_size;

        if (dtext->text) {

            av_log(ctx, AV_LOG_ERROR,

                   "Both text and text file provided. Please provide only one\n");

            return AVERROR(EINVAL);

        }

        if ((err = av_file_map(dtext->textfile, &textbuf, &textbuf_size, 0, ctx)) < 0) {

            av_log(ctx, AV_LOG_ERROR,

                   "The text file '%s' could not be read or is empty\n",

                   dtext->textfile);

            return err;

        }

        if (!(dtext->text = av_malloc(textbuf_size+1)))

            return AVERROR(ENOMEM);

        memcpy(dtext->text, textbuf, textbuf_size);

        dtext->text[textbuf_size] = 0;

        av_file_unmap(textbuf, textbuf_size);

    }

    if (!dtext->text) {

        av_log(ctx, AV_LOG_ERROR,

               "Either text or a valid file must be provided\n");

        return AVERROR(EINVAL);

    }

    if ((err = av_parse_color(dtext->fontcolor_rgba, dtext->fontcolor_string, -1, ctx))) {

        av_log(ctx, AV_LOG_ERROR,

               "Invalid font color '%s'\n", dtext->fontcolor_string);

        return err;

    }

    if ((err = av_parse_color(dtext->boxcolor_rgba, dtext->boxcolor_string, -1, ctx))) {

        av_log(ctx, AV_LOG_ERROR,

               "Invalid box color '%s'\n", dtext->boxcolor_string);

        return err;

    }

    if ((err = FT_Init_FreeType(&(dtext->library)))) {

        av_log(ctx, AV_LOG_ERROR,

               "Could not load FreeType: %s\n", FT_ERRMSG(err));

        return AVERROR(EINVAL);

    }

    /* load the face, and set up the encoding, which is by default UTF-8 */

    if ((err = FT_New_Face(dtext->library, dtext->fontfile, 0, &dtext->face))) {

        av_log(ctx, AV_LOG_ERROR, "Could not load fontface from file '%s': %s\n",

               dtext->fontfile, FT_ERRMSG(err));

        return AVERROR(EINVAL);

    }

    if ((err = FT_Set_Pixel_Sizes(dtext->face, 0, dtext->fontsize))) {

        av_log(ctx, AV_LOG_ERROR, "Could not set font size to %d pixels: %s\n",

               dtext->fontsize, FT_ERRMSG(err));

        return AVERROR(EINVAL);

    }

    dtext->use_kerning = FT_HAS_KERNING(dtext->face);

    /* load the fallback glyph with code 0 */

    load_glyph(ctx, NULL, 0);

#if !HAVE_LOCALTIME_R

    av_log(ctx, AV_LOG_WARNING, "strftime() expansion unavailable!\n");

#else

    if (strlen(dtext->text) >= MAX_EXPANDED_TEXT_SIZE) {

        av_log(ctx, AV_LOG_ERROR,

               "Impossible to print text, string is too big\n");

        return AVERROR(EINVAL);

    }

#endif

    return 0;

}

static int query_formats(AVFilterContext *ctx)

{

    static const enum PixelFormat pix_fmts[] = {

        PIX_FMT_ARGB,    PIX_FMT_RGBA,

        PIX_FMT_ABGR,    PIX_FMT_BGRA,

        PIX_FMT_RGB24,   PIX_FMT_BGR24,

        PIX_FMT_YUV420P, PIX_FMT_YUV444P,

        PIX_FMT_YUV422P, PIX_FMT_YUV411P,

        PIX_FMT_YUV410P, PIX_FMT_YUV440P,

        PIX_FMT_NONE

    };

    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));

    return 0;

}

static int glyph_enu_free(void *opaque, void *elem)

{

    av_free(elem);

    return 0;

}

static av_cold void uninit(AVFilterContext *ctx)

{

    DrawTextContext *dtext = ctx->priv;

    int i;

    av_freep(&dtext->fontfile);

    av_freep(&dtext->text);

    av_freep(&dtext->fontcolor_string);

    av_freep(&dtext->boxcolor_string);

    av_tree_enumerate(dtext->glyphs, NULL, NULL, glyph_enu_free);

    av_tree_destroy(dtext->glyphs);

    dtext->glyphs = 0;

    FT_Done_Face(dtext->face);

    FT_Done_FreeType(dtext->library);

    for (i = 0; i < 4; i++) {

        av_freep(&dtext->box_line[i]);

        dtext->pixel_step[i] = 0;

    }

}

static int config_input(AVFilterLink *inlink)

{

    DrawTextContext *dtext = inlink->dst->priv;

    const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[inlink->format];

    int ret;

    dtext->hsub = pix_desc->log2_chroma_w;

    dtext->vsub = pix_desc->log2_chroma_h;

    if ((ret =

         ff_fill_line_with_color(dtext->box_line, dtext->pixel_step,

                                 inlink->w, dtext->boxcolor,

                                 inlink->format, dtext->boxcolor_rgba,

                                 &dtext->is_packed_rgb, dtext->rgba_map)) < 0)

        return ret;

    if (!dtext->is_packed_rgb) {

        uint8_t *rgba = dtext->fontcolor_rgba;

        dtext->fontcolor[0] = RGB_TO_Y_CCIR(rgba[0], rgba[1], rgba[2]);

        dtext->fontcolor[1] = RGB_TO_U_CCIR(rgba[0], rgba[1], rgba[2], 0);

        dtext->fontcolor[2] = RGB_TO_V_CCIR(rgba[0], rgba[1], rgba[2], 0);

        dtext->fontcolor[3] = rgba[3];

    }

    return 0;

}

#define GET_BITMAP_VAL(r, c)                                            \

    bitmap->pixel_mode == FT_PIXEL_MODE_MONO ?                          \

        (bitmap->buffer[(r) * bitmap->pitch + ((c)>>3)] & (0x80 >> ((c)&7))) * 255 : \

         bitmap->buffer[(r) * bitmap->pitch +  (c)]

#define SET_PIXEL_YUV(picref, yuva_color, val, x, y, hsub, vsub) {           \

    luma_pos    = ((x)          ) + ((y)          ) * picref->linesize[0]; \

    chroma_pos1 = ((x) >> (hsub)) + ((y) >> (vsub)) * picref->linesize[1]; \

    chroma_pos2 = ((x) >> (hsub)) + ((y) >> (vsub)) * picref->linesize[2]; \

    alpha = (yuva_color[3] * (val)) / 255;                               \

    picref->data[0][luma_pos] = (alpha * yuva_color[0] + (255 - alpha) * picref->data[0][luma_pos]) >> 8; \

    alpha = (yuva_color[3] * (val)) / 224;                               \

    picref->data[1][chroma_pos1] = 16 + (alpha * (yuva_color[1]-16) + (224 - alpha) * (picref->data[1][chroma_pos1]-16)) / 224; \

    picref->data[2][chroma_pos2] = 16 + (alpha * (yuva_color[2]-16) + (224 - alpha) * (picref->data[2][chroma_pos2]-16)) / 224; \

}

static inline int draw_glyph_yuv(AVFilterBufferRef *picref, FT_Bitmap *bitmap, unsigned int x,

                                 unsigned int y, unsigned int width, unsigned int height,

                                 unsigned char yuva_color[4], int hsub, int vsub)

{

    int r, c, alpha;

    unsigned int luma_pos, chroma_pos1, chroma_pos2;

    uint8_t src_val, dst_pixel[4];

    for (r = 0; r < bitmap->rows && r+y < height; r++) {

        for (c = 0; c < bitmap->width && c+x < width; c++) {

            /* get pixel in the picref (destination) */

            dst_pixel[0] = picref->data[0][  c+x           +  (y+r)          * picref->linesize[0]];

            dst_pixel[1] = picref->data[1][((c+x) >> hsub) + ((y+r) >> vsub) * picref->linesize[1]];

            dst_pixel[2] = picref->data[2][((c+x) >> hsub) + ((y+r) >> vsub) * picref->linesize[2]];

            /* get intensity value in the glyph bitmap (source) */

            src_val = GET_BITMAP_VAL(r, c);

            if (!src_val)

                continue;

            SET_PIXEL_YUV(picref, yuva_color, src_val, c+x, y+r, hsub, vsub);

        }

    }

    return 0;

}

#define SET_PIXEL_RGB(picref, rgba_color, val, x, y, pixel_step, r_off, g_off, b_off, a_off) { \

    p   = picref->data[0] + (x) * pixel_step + ((y) * picref->linesize[0]); \

    alpha = (rgba_color[3] * (val)) / 255;                              \

    *(p+r_off) = (alpha * rgba_color[0] + (255 - alpha) * *(p+r_off)) >> 8; \

    *(p+g_off) = (alpha * rgba_color[1] + (255 - alpha) * *(p+g_off)) >> 8; \

    *(p+b_off) = (alpha * rgba_color[2] + (255 - alpha) * *(p+b_off)) >> 8; \

}

static inline int draw_glyph_rgb(AVFilterBufferRef *picref, FT_Bitmap *bitmap,

                                 unsigned int x, unsigned int y,

                                 unsigned int width, unsigned int height, int pixel_step,

                                 unsigned char rgba_color[4], uint8_t rgba_map[4])

{

    int r, c, alpha;

    uint8_t *p;

    uint8_t src_val, dst_pixel[4];

    for (r = 0; r < bitmap->rows && r+y < height; r++) {

        for (c = 0; c < bitmap->width && c+x < width; c++) {

            /* get pixel in the picref (destination) */

            dst_pixel[0] = picref->data[0][(c+x + rgba_map[0]) * pixel_step +

                                           (y+r) * picref->linesize[0]];

            dst_pixel[1] = picref->data[0][(c+x + rgba_map[1]) * pixel_step +

                                           (y+r) * picref->linesize[0]];

            dst_pixel[2] = picref->data[0][(c+x + rgba_map[2]) * pixel_step +

                                           (y+r) * picref->linesize[0]];

            /* get intensity value in the glyph bitmap (source) */

            src_val = GET_BITMAP_VAL(r, c);

            if (!src_val)

                continue;

            SET_PIXEL_RGB(picref, rgba_color, src_val, c+x, y+r, pixel_step,

                          rgba_map[0], rgba_map[1], rgba_map[2], rgba_map[3]);

        }

    }

    return 0;

}

static inline void drawbox(AVFilterBufferRef *picref, unsigned int x, unsigned int y,

                           unsigned int width, unsigned int height,

                           uint8_t *line[4], int pixel_step[4], uint8_t color[4],

                           int hsub, int vsub, int is_rgba_packed, uint8_t rgba_map[4])

{

    int i, j, alpha;

    if (color[3] != 0xFF) {

        if (is_rgba_packed) {

            uint8_t *p;

            for (j = 0; j < height; j++)

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

                    SET_PIXEL_RGB(picref, color, 255, i+x, y+j, pixel_step[0],

                                  rgba_map[0], rgba_map[1], rgba_map[2], rgba_map[3]);

        } else {

            unsigned int luma_pos, chroma_pos1, chroma_pos2;

            for (j = 0; j < height; j++)

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

                    SET_PIXEL_YUV(picref, color, 255, i+x, y+j, hsub, vsub);

        }

    } else {

        ff_draw_rectangle(picref->data, picref->linesize,

                          line, pixel_step, hsub, vsub,

                          x, y, width, height);

    }

}

static int draw_text(AVFilterContext *ctx, AVFilterBufferRef *picref,

                     int width, int height)

{

    DrawTextContext *dtext = ctx->priv;

    char *text = dtext->text;

    uint32_t code = 0, prev_code = 0;

    int x = 0, y = 0, i = 0;

    int text_height, baseline;

    uint8_t *p;

    int str_w, str_w_max;

    int y_min = 32000, y_max = -32000;

    FT_Vector delta;

    Glyph *glyph = NULL, *prev_glyph = NULL;

    Glyph dummy = { 0 };

#if HAVE_LOCALTIME_R

    time_t now = time(0);

    struct tm ltime;

    size_t expanded_text_len;

    dtext->expanded_text[0] = '\1';

    expanded_text_len = strftime(dtext->expanded_text, MAX_EXPANDED_TEXT_SIZE,

                                 text, localtime_r(&now, &ltime));

    text = dtext->expanded_text;

    if (expanded_text_len == 0 && dtext->expanded_text[0] != '\0') {

        av_log(ctx, AV_LOG_ERROR,

               "Impossible to print text, string is too big\n");

        return AVERROR(EINVAL);

    }

#endif

    str_w = str_w_max = 0;

    x = dtext->x;

    y = dtext->y;

    /* load and cache glyphs */

    for (i = 0, p = text; *p; i++) {

        GET_UTF8(code, *p++, continue;);

        /* get glyph */

        dummy.code = code;

        glyph = av_tree_find(dtext->glyphs, &dummy, (void *)glyph_cmp, NULL);

        if (!glyph)

            load_glyph(ctx, &glyph, code);

        y_min = FFMIN(glyph->bbox.yMin, y_min);

        y_max = FFMAX(glyph->bbox.yMax, y_max);

    }

    text_height = y_max - y_min;

    baseline    = y_max;

    /* compute and save position for each glyph */

    glyph = NULL;

    for (i = 0, p = text; *p; i++) {

        GET_UTF8(code, *p++, continue;);

        /* skip the \n in the sequence \r\n */

        if (prev_code == '\r' && code == '\n')

            continue;

        /* get glyph */

        prev_glyph = glyph;

        dummy.code = code;

        glyph = av_tree_find(dtext->glyphs, &dummy, (void *)glyph_cmp, NULL);

        /* kerning */

        if (dtext->use_kerning && prev_glyph && glyph->code) {

            FT_Get_Kerning(dtext->face, prev_glyph->code, glyph->code,

                           ft_kerning_default, &delta);

            x += delta.x >> 6;

        }

        if (x + glyph->advance >= width || code == '\r' || code == '\n') {

            if (x + glyph->advance >= width)

                str_w_max = width - dtext->x - 1;

            y += text_height;

            x = dtext->x;

        }

        /* save position */

        dtext->positions[i].x = x + glyph->bitmap_left;

        dtext->positions[i].y = y - glyph->bitmap_top + baseline;

        if (code != '\n' && code != '\r') {

            int advance = glyph->advance;

            if (code == '\t')

                advance *= dtext->tabsize;

            x     += advance;

            str_w += advance;

        }

        prev_code = code;

    }

    y += text_height;

    if (str_w_max == 0)

        str_w_max = str_w;

    /* draw box */

    if (dtext->draw_box) {

        /* check if it doesn't pass the limits */

        str_w_max = FFMIN(str_w_max, width - dtext->x - 1);

        y = FFMIN(y, height - 1);

        /* draw background */

        drawbox(picref, dtext->x, dtext->y, str_w_max, y-dtext->y,

                dtext->box_line, dtext->pixel_step, dtext->boxcolor,

                dtext->hsub, dtext->vsub, dtext->is_packed_rgb, dtext->rgba_map);

    }

    /* draw glyphs */

    for (i = 0, p = text; *p; i++) {

        Glyph dummy = { 0 };

        GET_UTF8(code, *p++, continue;);

        /* skip new line chars, just go to new line */

        if (code == '\n' || code == '\r' || code == '\t')

            continue;

        dummy.code = code;

        glyph = av_tree_find(dtext->glyphs, &dummy, (void *)glyph_cmp, NULL);

        if (glyph->bitmap.pixel_mode != FT_PIXEL_MODE_MONO &&

            glyph->bitmap.pixel_mode != FT_PIXEL_MODE_GRAY)

            return AVERROR(EINVAL);

        if (dtext->is_packed_rgb) {

            draw_glyph_rgb(picref, &glyph->bitmap,

                           dtext->positions[i].x, dtext->positions[i].y, width, height,

                           dtext->pixel_step[0], dtext->fontcolor_rgba, dtext->rgba_map);

        } else {

            draw_glyph_yuv(picref, &glyph->bitmap,

                           dtext->positions[i].x, dtext->positions[i].y, width, height,

                           dtext->fontcolor, dtext->hsub, dtext->vsub);

        }

    }

    return 0;

}

static void null_draw_slice(AVFilterLink *link, int y, int h, int slice_dir) { }

static void end_frame(AVFilterLink *inlink)

{

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

    AVFilterBufferRef *picref = inlink->cur_buf;

    draw_text(inlink->dst, picref, picref->video->w, picref->video->h);

    avfilter_draw_slice(outlink, 0, picref->video->h, 1);

    avfilter_end_frame(outlink);

}

AVFilter avfilter_vf_drawtext = {

    .name          = "drawtext",

    .description   = NULL_IF_CONFIG_SMALL("Draw text on top of video frames using libfreetype library."),

    .priv_size     = sizeof(DrawTextContext),

    .init          = init,

    .uninit        = uninit,

    .query_formats = query_formats,

    .inputs    = (AVFilterPad[]) {{ .name             = "default",

                                    .type             = AVMEDIA_TYPE_VIDEO,

                                    .get_video_buffer = avfilter_null_get_video_buffer,

                                    .start_frame      = avfilter_null_start_frame,

                                    .draw_slice       = null_draw_slice,

                                    .end_frame        = end_frame,

                                    .config_props     = config_input,

                                    .min_perms        = AV_PERM_WRITE |

                                                        AV_PERM_READ,

                                    .rej_perms        = AV_PERM_PRESERVE },

                                  { .name = NULL}},

    .outputs   = (AVFilterPad[]) {{ .name             = "default",

                                    .type             = AVMEDIA_TYPE_VIDEO, },

                                  { .name = NULL}},

};