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author | Stefano Sabatini <stefasab@gmail.com> | 2011-09-18 04:41:56 +0400 |
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committer | Stefano Sabatini <stefasab@gmail.com> | 2011-09-24 14:36:48 +0400 |
commit | 482ce0ce4ec558db5a951718bcd7a9c01d0afb36 (patch) | |
tree | 57f5b0573963ebe6e868538fe6cbae0f2ac05473 /doc/filters.texi | |
parent | 163854bca0e0c1b43831de7463ffa3ff9e6595ca (diff) |
vf_drawtext: make x and y options parametric
Address trac issue #378.
Diffstat (limited to 'doc/filters.texi')
-rw-r--r-- | doc/filters.texi | 96 |
1 files changed, 93 insertions, 3 deletions
diff --git a/doc/filters.texi b/doc/filters.texi index 4df49d96a3..b40dc5d7b7 100644 --- a/doc/filters.texi +++ b/doc/filters.texi @@ -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: |