[FFmpeg-devel] [PATCH] added expr evaluation to drawtext - fontsize

[Brett Harrison]

Most recent patch.  I was evaluating fontsize too early before when using
the 'n' variable in equations.

On Thu, Sep 1, 2016 at 3:44 PM, Brett Harrison <brett.harrison at zyamusic.com>
wrote:

> Any feedback on this newest patch?
>
> On Tue, Aug 30, 2016 at 2:17 PM, Brett Harrison <
> brett.harrison at zyamusic.com> wrote:
>
>> Since there are differing opinions on how the default fontsize should be
>> established this patch adds my changes while preserving the current
>> behavior when fontsize is not specified.
>>
>> On Tue, Aug 30, 2016 at 2:43 AM, Nicolas George <george at nsup.org> wrote:
>>
>>> Le tridi 13 fructidor, an CCXXIV, Brett Harrison a écrit :
>>> > Before I fix the patch, can you clarify the intended functionality?
>>> >
>>> > The docs say that 16 is the default fontsize, however if
>>> > CONFIG_LIBFONTCONFIG is configured and ffmpeg if called with:
>>> >
>>> > -vf drawtext=text=abc:fontcolor=white
>>> >
>>> > on my system the font used will be /opt/X11/share/fonts/TTF/Vera.ttf
>>> (the
>>> > default chosen by libfontconfig) and the fontsize will be set to 12.
>>> >
>>> > However if ffmpeg is called with:
>>> >
>>> > -vf
>>> > drawtext=text=abc:fontcolor=white:fontfile=/opt/X11/share/fo
>>> nts/TTF/Vera.ttf
>>> >
>>> > This is the same font that libfontconfig used, however this time
>>> fontsize
>>> > 16 is used as stated in the docs.
>>> >
>>> > The difference is this line of code in load_font_fontconfig
>>> >   if (!s->fontsize)
>>> >         s->fontsize = size + 0.5;
>>> >
>>> > I didn't set the fontsize in either command, but the output was
>>> different.
>>> > Do we want to keep this as is?
>>>
>>> I think the current behaviour is correct.
>>>
>>> I start with the following principle: when users want something precise
>>> about aesthetic or other arbitrary settings, they have to say it.
>>>
>>> Default values are for the lazy or the careless ones: quick profiling and
>>> testing when the exact result does not matter much. But as soon as the
>>> result matters, explicit values must be given.
>>>
>>> Do not take me wrong, the default values should be, as much as possible,
>>> sensible. But for a font size, 12 is as sensible as 16.
>>>
>>> Most importantly, backward compatibility should not be an hindrance to
>>> choosing better default values. We should not change them lightly, but
>>> not
>>> feel forbidden to do so either.
>>>
>>> Fontconfig is not just a path search library for finding font files. It
>>> is a
>>> complete mechanism for choosing the right font according to several
>>> conditions set by the user. Including the font size.
>>>
>>> There are no less than four levels for choosing the font size:
>>>
>>> (1) lavfi's default, 16;
>>>
>>> (2) fontconfig's default;
>>>
>>> (3) fontconfig's explicit value, as in "Times-12:bold";
>>>
>>> (4) lavfi's explicit value, as in "fontsize=16".
>>>
>>> I think the order of precedence should be just that, for the following
>>> reasons:
>>>
>>> - First, of course, (3), (4) > (1), (2), because explicit values are
>>> always
>>>   more important.
>>>
>>> - Second, conflicting explicit values are the users' problem. We can
>>> produce
>>>   warnings to help diagnose, but in the end it is their choice. (4) >
>>> (3) is
>>>   slightly easier to implement (distinguishing (3) from (2) requires a
>>> bit
>>>   of work), and (4) is more supple, especially when your patch gets
>>> applied.
>>>
>>> - Last, (2) > (1), because fontconfig is more cross-applications than
>>> lavfi,
>>>   and also because it includes a mechanism for explicit configuration.
>>>
>>> Still, the documentation should be clarified, possibly something like
>>> that:
>>> "The default value of fontsize is provided by fontconfig if in use or 16
>>> when using a font file directly."
>>>
>>> Regards,
>>>
>>> --
>>>   Nicolas George
>>>
>>> _______________________________________________
>>> ffmpeg-devel mailing list
>>> ffmpeg-devel at ffmpeg.org
>>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>>
>>>
>>
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-added-expr-evaluation-to-drawtext-fontsize.patch
Type: application/octet-stream
Size: 8824 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20160901/7c6ac3ee/attachment.obj>