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Posted to dev@openoffice.apache.org by "Dennis E. Hamilton" <de...@acm.org> on 2011/12/05 23:29:03 UTC
SVG Image Rasterization (was RE: [Code] strategy for "child works spaces")
Without looking, but based on how Eric described the effect, I believe it is aliasing on the monitor if not elsewhere in the pipeline. Especially if it shows a Moiré pattern.
There are an amazing number of places in the rendering pipeline where something could be off, especially if there is any intermediate resampling.
It is a function of rasterization of the image.
- Dennis
PS: The funniest case for me is when I attempt to take pictures of my computer LCD display with my digital camera. The LCD preview on the back of the camera shows unbelievably bad Moiré (think of the number of times resampling, especially down-sampling, is being done), but if I zoom into the image on the camera's LCD display I find that the 10 Mpixel digital image is often -- not always -- clean and without much aliasing, if any. (My manual anti-aliasing procedure is to defocus the image slightly.)
-----Original Message-----
From: eric b [mailto:eric.bachard@free.fr]
Sent: Monday, December 05, 2011 09:57
To: ooo-dev@incubator.apache.org
Subject: Re: [Code] strategy for "child works spaces"
Hi,
Le 5 déc. 11 à 18:51, Rory O'Farrell a écrit :
> On Mon, 5 Dec 2011 18:40:14 +0100
> eric b <er...@free.fr> wrote:
> <snip>
>> 2) Opening an .svg containing gradients, I played with the zoom,
>> until a big value, and the only strange issue I saw was sort of
>> spatial filtering, say spectral effect, like aliasing in the areas
>> containing the gradient. After some tries, the phenomen occurs
>> every times for some well defined zoom values (sorry if I'm not
>> clear).
>
> Do you mean that the continuous tone gradient resolves into dicrete
> tonal steps?
>
Something lke that, yes. In applied optics (my job in the real life)
the name is "aliasing", but I'm unsure this is what we observe here.
If you want to verify, I can provide a link to download Mac OS X
Intel build, either german, english or french (apologies, Windows is
not finished yet).
Regards,
Eric
--
qɔᴉɹə
Projet OOo4Kids : http://wiki.ooo4kids.org/index.php/Main_Page
L'association EducOOo : http://www.educoo.org
Blog : http://eric.bachard.org/news
Re: SVG Image Rasterization (was RE: [Code] strategy for "child works spaces")
Posted by Rob Weir <ro...@apache.org>.
On Mon, Dec 5, 2011 at 5:29 PM, Dennis E. Hamilton
<de...@acm.org> wrote:
> Without looking, but based on how Eric described the effect, I believe it is aliasing on the monitor if not elsewhere in the pipeline. Especially if it shows a Moiré pattern.
>
If it is a gradient, and it happens at high zooms, then this could be banding.
http://en.wikipedia.org/wiki/Colour_banding
-Rob
> There are an amazing number of places in the rendering pipeline where something could be off, especially if there is any intermediate resampling.
>
> It is a function of rasterization of the image.
>
> - Dennis
>
> PS: The funniest case for me is when I attempt to take pictures of my computer LCD display with my digital camera. The LCD preview on the back of the camera shows unbelievably bad Moiré (think of the number of times resampling, especially down-sampling, is being done), but if I zoom into the image on the camera's LCD display I find that the 10 Mpixel digital image is often -- not always -- clean and without much aliasing, if any. (My manual anti-aliasing procedure is to defocus the image slightly.)
>
>
> -----Original Message-----
> From: eric b [mailto:eric.bachard@free.fr]
> Sent: Monday, December 05, 2011 09:57
> To: ooo-dev@incubator.apache.org
> Subject: Re: [Code] strategy for "child works spaces"
>
> Hi,
>
> Le 5 déc. 11 à 18:51, Rory O'Farrell a écrit :
>
>> On Mon, 5 Dec 2011 18:40:14 +0100
>> eric b <er...@free.fr> wrote:
>> <snip>
>>> 2) Opening an .svg containing gradients, I played with the zoom,
>>> until a big value, and the only strange issue I saw was sort of
>>> spatial filtering, say spectral effect, like aliasing in the areas
>>> containing the gradient. After some tries, the phenomen occurs
>>> every times for some well defined zoom values (sorry if I'm not
>>> clear).
>>
>> Do you mean that the continuous tone gradient resolves into dicrete
>> tonal steps?
>>
>
> Something lke that, yes. In applied optics (my job in the real life)
> the name is "aliasing", but I'm unsure this is what we observe here.
>
> If you want to verify, I can provide a link to download Mac OS X
> Intel build, either german, english or french (apologies, Windows is
> not finished yet).
>
>
> Regards,
> Eric
>
> --
> qɔᴉɹə
> Projet OOo4Kids : http://wiki.ooo4kids.org/index.php/Main_Page
> L'association EducOOo : http://www.educoo.org
> Blog : http://eric.bachard.org/news
>
>
>
>
>
>