[FFmpeg-devel] [PATCH] adjust y in pad filter

Baptiste Coudurier baptiste.coudurier
Tue May 11 23:55:44 CEST 2010

On 05/11/2010 02:38 PM, Michael Niedermayer wrote:
> On Tue, May 11, 2010 at 10:55:22PM +0200, Reimar D?ffinger wrote:
>> On Tue, May 11, 2010 at 12:38:29PM -0700, Baptiste Coudurier wrote:
>>> On 05/11/2010 12:32 PM, Reimar D?ffinger wrote:
>>>> On Tue, May 11, 2010 at 11:04:48AM -0700, Baptiste Coudurier wrote:
>>>>> On 05/11/2010 10:55 AM, Baptiste Coudurier wrote:
>>>>>> On 05/11/2010 10:50 AM, Reimar D?ffinger wrote:
>>>>>>> On Tue, May 11, 2010 at 10:33:51AM -0700, Baptiste Coudurier wrote:
>>>>>>>> I believe that it is simpler and obvious for everybody that
>>>>>>>> 0,0 coordinates are bottom left corner and not top left corner.
>>>>>>> Not to me, I've never understood why it should be, does anyone
>>>>>>> number line numbers on a page from bottom to top?
>>>>>>> Why the should pixels suddenly be counted that way?
>>>>>> What about maths ?
>>>>> To elaborate, it is about geometry.
>>>>> In geometry, 0,0 is bottom left.
>>>> No, 0,0 is just the distinguished point, there's no "left", "bottom" or
>>>> whatever in geometry, even if it is usually drawn like that.
>>> Just stop here. That's what I'm talking about, "usually drawn", you
>>> just agreed with me, and I bet 90% of the _users_ of the filter.
>> Hard for me to imagine that 90% of users would expect the pad filter to
>> take geometric coordinates the way they were illustrated in their maths
>> books but using pixels as units and only accepting integer values instead
>> of assuming it would use pixel indexes just like their photo editing
>> applications...
> putting the origin at the top left makes sense for left-to-right writing
> people. i dont think it makes sense to people who primarely
> used right to left scripts in their lifes. And i wonder what the han/kanji
> using people would think of this.
> i really think we could expend this bikeshed by involving them

Well, I really think you guys are so much involved in graphic 
development and array adressing that your view is altered.

When I refer to x and y as coordinates, it really seems obvious to me, 
that they refer to the geometric meaning of placing a figure, and I 
think this is exactly what the pad filter is about according to its 
parameters: width:height:x:y

  h _______________
   |               |
   |   _________   |
   |  |         |  |
  y|  |_________|  |
   |               |
   0  x            w

This is pretty agnostic from the way people are writing text IMHO.

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