@@ -738,10 +738,13 @@ parameter @var{text}.

 If both text and textfile are specified, an error is thrown.

 @item x, y

-The offsets where text will be drawn within the video frame.

-Relative to the top/left border of the output image.

+The expressions which specify the offsets where text will be drawn

+within the video frame. They are relative to the top/left border of the

+output image.

-The default value of @var{x} and @var{y} is 0.

+The default value of @var{x} and @var{y} is "0".

+

+See below for the list of accepted constants.

 @item fontsize

 The font size to be used for drawing text.

@@ -809,6 +812,66 @@ The size in number of spaces to use for rendering the tab.

 Default value is 4.

 @end table

+The parameters for @var{x} and @var{y} are expressions containing the

+following constants:

+

+@table @option

+@item E, PI, PHI

+the corresponding mathematical approximated values for e

+(euler number), pi (greek PI), PHI (golden ratio)

+

+@item w, h

+the input width and heigth

+

+@item tw, text_w

+the width of the rendered text

+

+@item th, text_h

+the height of the rendered text

+

+@item lh, line_h

+the height of each text line

+

+@item sar

+input sample aspect ratio

+

+@item dar

+input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}

+

+@item hsub, vsub

+horizontal and vertical chroma subsample values. For example for the

+pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.

+

+@item max_glyph_w

+maximum glyph width, that is the maximum width for all the glyphs

+contained in the rendered text

+

+@item max_glyph_h

+maximum glyph height, that is the maximum height for all the glyphs

+contained in the rendered text, it is equivalent to @var{ascent} -

+@var{descent}.

+

+@item max_glyph_a, ascent

+

+the maximum distance from the baseline to the highest/upper grid

+coordinate used to place a glyph outline point, for all the rendered

+glyphs.

+It is a positive value, due to the grid's orientation with the Y axis

+upwards.

+

+@item max_glyph_d, descent

+the maximum distance from the baseline to the lowest grid coordinate

+used to place a glyph outline point, for all the rendered glyphs.

+This is a negative value, due to the grid's orientation, with the Y axis

+upwards.

+

+@item n

+the number of input frame, starting from 0

+

+@item t

+timestamp expressed in seconds, NAN if the input timestamp is unknown

+@end table

+

 Some examples follow.

 @itemize

@@ -835,6 +898,33 @@ drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test

 Note that the double quotes are not necessary if spaces are not used

 within the parameter list.

+@item

+Show the text at the center of the video frame:

+@example

+drawtext=fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"

+@end example

+

+@item

+Show a text line sliding from right to left in the last row of the video

+frame. The file @file{LONG_LINE} is assumed to contain a single line

+with no newlines.

+@example

+drawtext=fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t

+@end example

+

+@item

+Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.

+@example

+drawtext=fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"

+@end example

+

+@item

+Draw a single green letter "g", at the center of the input video.

+The glyph baseline is placed at half screen height.

+@example

+drawtext=fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent

+@end example

+

 @end itemize

 For more information about libfreetype, check:

@@ -30,7 +30,7 @@

 #define LIBAVFILTER_VERSION_MAJOR  2

 #define LIBAVFILTER_VERSION_MINOR 43

-#define LIBAVFILTER_VERSION_MICRO  4

+#define LIBAVFILTER_VERSION_MICRO  5

 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

                                                LIBAVFILTER_VERSION_MINOR, \

@@ -30,6 +30,7 @@

 #include <time.h>

 #include "libavutil/colorspace.h"

+#include "libavutil/eval.h"

 #include "libavutil/file.h"

 #include "libavutil/opt.h"

 #include "libavutil/parseutils.h"

@@ -45,6 +46,54 @@

 #include FT_FREETYPE_H

 #include FT_GLYPH_H

+static const char *var_names[] = {

+    "E",

+    "PHI",

+    "PI",

+    "w",                      ///< width  of the input video

+    "h",                      ///< height of the input video

+    "tw", "text_w",           ///< width  of the rendered text

+    "th", "text_h",           ///< height of the rendered text

+    "max_glyph_w",            ///< max glyph width

+    "max_glyph_h",            ///< max glyph height

+    "max_glyph_a", "ascent",  ///< max glyph ascent

+    "max_glyph_d", "descent", ///< min glyph descent

+    "line_h", "lh",           ///< line height, same as max_glyph_h

+    "sar",

+    "dar",

+    "hsub",

+    "vsub",

+    "x",

+    "y",

+    "n",                      ///< number of frame

+    "t",                      ///< timestamp expressed in seconds

+    NULL

+};

+

+enum var_name {

+    VAR_E,

+    VAR_PHI,

+    VAR_PI,

+    VAR_W,

+    VAR_H,

+    VAR_TW, VAR_TEXT_W,

+    VAR_TH, VAR_TEXT_H,

+    VAR_MAX_GLYPH_W,

+    VAR_MAX_GLYPH_H,

+    VAR_MAX_GLYPH_A, VAR_ASCENT,

+    VAR_MAX_GLYPH_D, VAR_DESCENT,

+    VAR_LINE_H, VAR_LH,

+    VAR_SAR,

+    VAR_DAR,

+    VAR_HSUB,

+    VAR_VSUB,

+    VAR_X,

+    VAR_Y,

+    VAR_N,

+    VAR_T,

+    VAR_VARS_NB

+};

+

 typedef struct {

     const AVClass *class;

     uint8_t *fontfile;              ///< font to be used

@@ -57,6 +106,11 @@ typedef struct {

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

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

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

+    char *x_expr;                   ///< expression for x position

+    char *y_expr;                   ///< expression for y position

+    AVExpr *x_pexpr, *y_pexpr;      ///< parsed expressions for x and y

+    int max_glyph_w;                ///< max glyph width

+    int max_glyph_h;                ///< max glyph heigth

     int shadowx, shadowy;

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

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

@@ -82,6 +136,7 @@ typedef struct {

     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

     int64_t basetime;               ///< base pts time in the real world for display

+    double var_values[VAR_VARS_NB];

 } DrawTextContext;

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

@@ -95,8 +150,8 @@ static const AVOption drawtext_options[]= {

 {"shadowcolor", "set shadow color",  OFFSET(shadowcolor_string), FF_OPT_TYPE_STRING, {.str=NULL},  CHAR_MIN, CHAR_MAX },

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

 {"fontsize", "set font size",        OFFSET(fontsize),           FF_OPT_TYPE_INT,    {.dbl=16},    1,        INT_MAX  },

-{"x",        "set x",                OFFSET(x),                  FF_OPT_TYPE_INT,    {.dbl=0},     0,        INT_MAX  },

-{"y",        "set y",                OFFSET(y),                  FF_OPT_TYPE_INT,    {.dbl=0},     0,        INT_MAX  },

+{"x",        "set x expression",     OFFSET(x_expr),             FF_OPT_TYPE_STRING, {.str="0"},   CHAR_MIN, CHAR_MAX },

+{"y",        "set y expression",     OFFSET(y_expr),             FF_OPT_TYPE_STRING, {.str="0"},   CHAR_MIN, CHAR_MAX },

 {"shadowx",  "set x",                OFFSET(shadowx),            FF_OPT_TYPE_INT,    {.dbl=0},     INT_MIN,  INT_MAX  },

 {"shadowy",  "set y",                OFFSET(shadowy),            FF_OPT_TYPE_INT,    {.dbl=0},     INT_MIN,  INT_MAX  },

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

@@ -348,12 +403,18 @@ static av_cold void uninit(AVFilterContext *ctx)

     DrawTextContext *dtext = ctx->priv;

     int i;

+    av_expr_free(dtext->x_pexpr); dtext->x_pexpr = NULL;

+    av_expr_free(dtext->y_pexpr); dtext->y_pexpr = NULL;

+

     av_freep(&dtext->fontfile);

     av_freep(&dtext->text);

     av_freep(&dtext->expanded_text);

     av_freep(&dtext->fontcolor_string);

     av_freep(&dtext->boxcolor_string);

     av_freep(&dtext->positions);

+    av_freep(&dtext->x_expr);

+    av_freep(&dtext->y_expr);

+

     dtext->nb_positions = 0;

     av_freep(&dtext->shadowcolor_string);

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

@@ -371,6 +432,7 @@ static av_cold void uninit(AVFilterContext *ctx)

 static int config_input(AVFilterLink *inlink)

 {

+    AVFilterContext *ctx = inlink->dst;

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

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

     int ret;

@@ -398,6 +460,26 @@ static int config_input(AVFilterLink *inlink)

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

     }

+    dtext->var_values[VAR_E]     = M_E;

+    dtext->var_values[VAR_PHI]   = M_PHI;

+    dtext->var_values[VAR_PI]    = M_PI;

+    dtext->var_values[VAR_W]     = inlink->w;

+    dtext->var_values[VAR_H]     = inlink->h;

+    dtext->var_values[VAR_SAR]   = inlink->sample_aspect_ratio.num ? av_q2d(inlink->sample_aspect_ratio) : 1;

+    dtext->var_values[VAR_DAR]   = (double)inlink->w / inlink->h * dtext->var_values[VAR_SAR];

+    dtext->var_values[VAR_HSUB]  = 1<<pix_desc->log2_chroma_w;

+    dtext->var_values[VAR_VSUB]  = 1<<pix_desc->log2_chroma_h;

+    dtext->var_values[VAR_X]     = NAN;

+    dtext->var_values[VAR_Y]     = NAN;

+    dtext->var_values[VAR_N]     = 0;

+    dtext->var_values[VAR_T]     = NAN;

+

+    if ((ret = av_expr_parse(&dtext->x_pexpr, dtext->x_expr, var_names,

+                             NULL, NULL, NULL, NULL, 0, ctx)) < 0 ||

+        (ret = av_expr_parse(&dtext->y_pexpr, dtext->y_expr, var_names,

+                             NULL, NULL, NULL, NULL, 0, ctx)) < 0)

+        return AVERROR(EINVAL);

+

     return 0;

 }

@@ -441,6 +523,9 @@ static inline int draw_glyph_yuv(AVFilterBufferRef *picref, FT_Bitmap *bitmap,

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

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

+            if (c+x < 0 || r+y < 0)

+                continue;

+

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

             src_val = GET_BITMAP_VAL(r, c);

             if (!src_val)

@@ -471,6 +556,8 @@ static inline int draw_glyph_rgb(AVFilterBufferRef *picref, FT_Bitmap *bitmap,

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

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

+            if (c+x < 0 || r+y < 0)

+                continue;

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

             src_val = GET_BITMAP_VAL(r, c);

             if (!src_val)

@@ -521,7 +608,7 @@ static int draw_glyphs(DrawTextContext *dtext, AVFilterBufferRef *picref,

 {

     char *text = dtext->expanded_text;

     uint32_t code = 0;

-    int i;

+    int i, x1, y1;

     uint8_t *p;

     Glyph *glyph = NULL;

@@ -540,13 +627,16 @@ static int draw_glyphs(DrawTextContext *dtext, AVFilterBufferRef *picref,

             glyph->bitmap.pixel_mode != FT_PIXEL_MODE_GRAY)

             return AVERROR(EINVAL);

+        x1 = dtext->positions[i].x+dtext->x+x;

+        y1 = dtext->positions[i].y+dtext->y+y;

+

         if (dtext->is_packed_rgb) {

             draw_glyph_rgb(picref, &glyph->bitmap,

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

+                           x1, y1, width, height,

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

         } else {

             draw_glyph_yuv(picref, &glyph->bitmap,

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

+                           x1, y1, width, height,

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

         }

     }

@@ -560,11 +650,12 @@ static int draw_text(AVFilterContext *ctx, AVFilterBufferRef *picref,

     DrawTextContext *dtext = ctx->priv;

     uint32_t code = 0, prev_code = 0;

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

-    int text_height;

+    int max_text_line_w = 0, len;

+    int box_w, box_h;

     char *text = dtext->text;

     uint8_t *p;

-    int str_w = 0, len;

     int y_min = 32000, y_max = -32000;

+    int x_min = 32000, x_max = -32000;

     FT_Vector delta;

     Glyph *glyph = NULL, *prev_glyph = NULL;

     Glyph dummy = { 0 };

@@ -607,8 +698,8 @@ static int draw_text(AVFilterContext *ctx, AVFilterBufferRef *picref,

         dtext->nb_positions = len;

     }

-    x = dtext->x;

-    y = dtext->y;

+    x = 0;

+    y = 0;

     /* load and cache glyphs */

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

@@ -622,8 +713,11 @@ static int draw_text(AVFilterContext *ctx, AVFilterBufferRef *picref,

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

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

+        x_min = FFMIN(glyph->bbox.xMin, x_min);

+        x_max = FFMAX(glyph->bbox.xMax, x_max);

     }

-    text_height = y_max - y_min;

+    dtext->max_glyph_h = y_max - y_min;

+    dtext->max_glyph_w = x_max - x_min;

     /* compute and save position for each glyph */

     glyph = NULL;

@@ -636,9 +730,9 @@ static int draw_text(AVFilterContext *ctx, AVFilterBufferRef *picref,

         prev_code = code;

         if (is_newline(code)) {

-            str_w = FFMAX(str_w, x - dtext->x);

-            y += text_height;

-            x = dtext->x;

+            max_text_line_w = FFMAX(max_text_line_w, x);

+            y += dtext->max_glyph_h;

+            x = 0;

             continue;

         }

@@ -661,12 +755,31 @@ static int draw_text(AVFilterContext *ctx, AVFilterBufferRef *picref,

         else              x += glyph->advance;

     }

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

-    y     = FFMIN(y + text_height, height - 1);

+    max_text_line_w = FFMAX(x, max_text_line_w);

+

+    dtext->var_values[VAR_TW] = dtext->var_values[VAR_TEXT_W] = max_text_line_w;

+    dtext->var_values[VAR_TH] = dtext->var_values[VAR_TEXT_H] = y + dtext->max_glyph_h;

+

+    dtext->var_values[VAR_MAX_GLYPH_W] = dtext->max_glyph_w;

+    dtext->var_values[VAR_MAX_GLYPH_H] = dtext->max_glyph_h;

+    dtext->var_values[VAR_MAX_GLYPH_A] = dtext->var_values[VAR_ASCENT ] = y_max;

+    dtext->var_values[VAR_MAX_GLYPH_D] = dtext->var_values[VAR_DESCENT] = y_min;

+

+    dtext->var_values[VAR_LINE_H] = dtext->var_values[VAR_LH] = dtext->max_glyph_h;

+

+    dtext->x = dtext->var_values[VAR_X] = av_expr_eval(dtext->x_pexpr, dtext->var_values, NULL);

+    dtext->y = dtext->var_values[VAR_Y] = av_expr_eval(dtext->y_pexpr, dtext->var_values, NULL);

+    dtext->x = dtext->var_values[VAR_X] = av_expr_eval(dtext->x_pexpr, dtext->var_values, NULL);

+

+    dtext->x &= ~((1 << dtext->hsub) - 1);

+    dtext->y &= ~((1 << dtext->vsub) - 1);

+

+    box_w = FFMIN(width - 1 , max_text_line_w);

+    box_h = FFMIN(height - 1, y + dtext->max_glyph_h);

     /* draw box */

     if (dtext->draw_box)

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

+        drawbox(picref, dtext->x, dtext->y, box_w, box_h,

                 dtext->box_line, dtext->pixel_step, dtext->boxcolor_rgba,

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

@@ -688,9 +801,21 @@ 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];

+    AVFilterContext *ctx = inlink->dst;

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

     AVFilterBufferRef *picref = inlink->cur_buf;

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

+    dtext->var_values[VAR_T] = picref->pts == AV_NOPTS_VALUE ?

+        NAN : picref->pts * av_q2d(inlink->time_base);

+

+    draw_text(ctx, picref, picref->video->w, picref->video->h);

+

+    av_log(ctx, AV_LOG_DEBUG, "n:%d t:%f text_w:%d text_h:%d x:%d y:%d\n",

+           (int)dtext->var_values[VAR_N], dtext->var_values[VAR_T],

+           (int)dtext->var_values[VAR_TEXT_W], (int)dtext->var_values[VAR_TEXT_H],

+           dtext->x, dtext->y);

+

+    dtext->var_values[VAR_N] += 1.0;

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

     avfilter_end_frame(outlink);