Curious effect

http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this
image. Depending on the software and level of
zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm
door with a screen in it. There's a pattern of hill-
shaped lines, alternating darker and lighter. That's
the actual image. But at some zooms it also shows
what looks like a shadow of the screen on the snow,
or dark lines coming from the lower left and swooping
up. I can't think how it could be happening, since
the image pixel data is not changed. Maybe the
combination of patterns is somehow distorting the
resizing algorythm? I've never seen anything like it.

On Tue, 3 Feb 2015 22:18:13 -0500, "Mayayana"
wrote:

http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this
image. Depending on the software and level of
zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm
door with a screen in it. There's a pattern of hill-
shaped lines, alternating darker and lighter. That's
the actual image. But at some zooms it also shows
what looks like a shadow of the screen on the snow,
or dark lines coming from the lower left and swooping
up. I can't think how it could be happening, since
the image pixel data is not changed. Maybe the
combination of patterns is somehow distorting the
resizing algorythm? I've never seen anything like it.


Separate snow falls? Even though snow may fall continually it may not
be faling constantly.
--

Regards,

Eric Stevens

In article , Mayayana
wrote:

http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this
image. Depending on the software and level of
zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm
door with a screen in it. There's a pattern of hill-
shaped lines, alternating darker and lighter. That's
the actual image. But at some zooms it also shows
what looks like a shadow of the screen on the snow,
or dark lines coming from the lower left and swooping
up. I can't think how it could be happening, since
the image pixel data is not changed. Maybe the
combination of patterns is somehow distorting the
resizing algorythm? I've never seen anything like it.

if you mean the layering of the snow, that's from the wind.

you also should replace the two cracked panes.

In article , Mayayana wrote:

http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this image. Depending on
the software and level of zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm door with a screen
in it. There's a pattern of hill- shaped lines, alternating darker
and lighter. That's the actual image. But at some zooms it also
shows what looks like a shadow of the screen on the snow, or dark
lines coming from the lower left and swooping up. I can't think how
it could be happening, since the image pixel data is not changed.
Maybe the combination of patterns is somehow distorting the resizing
algorythm? I've never seen anything like it.

The effect you're describing is moire, like you said. It all depends on how your
web browser scales the image. In 100% zoom there is nothing, but when you
downscale the image, the scaling creates patterns out of the repeating pattern of
the screen door, which makes for some interesting lines.

I can only see it while resizing the window, not when I release it, at which
point OSX re-renders the image in a lower resolution, and the moire is not
apparent.

I trust this is the effect you're seeing:

http://jonaseklundh.se/files/moire.png

--
Sandman

On 02/03/2015 09:18 PM, Mayayana wrote:
http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this
image. Depending on the software and level of
zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm
door with a screen in it. There's a pattern of hill-
shaped lines, alternating darker and lighter. That's
the actual image. But at some zooms it also shows
what looks like a shadow of the screen on the snow,
or dark lines coming from the lower left and swooping
up. I can't think how it could be happening, since
the image pixel data is not changed. Maybe the
combination of patterns is somehow distorting the
resizing algorythm? I've never seen anything like it.





The moire pattern is because there is a screen in the window I presume.

| The effect you're describing is moire, like you said. It all depends on
how your
| web browser scales the image. In 100% zoom there is nothing, but when you
| downscale the image, the scaling creates patterns out of the repeating
pattern of
| the screen door, which makes for some interesting lines.
|
| I can only see it while resizing the window, not when I release it, at
which
| point OSX re-renders the image in a lower resolution, and the moire is not
| apparent.
|
| I trust this is the effect you're seeing:
|
| http://jonaseklundh.se/files/moire.png
|

Yes. Thanks. The easiest way to show it is just
to view the image full and then resize to fit the
window. (In Firefox/Pale Moon, at least, I can
click the browser window to toggle between views.
I'm guessing other browsers are the same.)
Though the effect varies at different sizes. Sizing
it down to 640w in some cases eliminated the effect.

I looked at the Wikipedia entry for moire and can't
say I really understand how it happens, but it sounds
like it could be a result of imperfect aliasing as part
of the resizing routine. So strange. I never would have
guessed that such an error could be inherent in the
basic mathematical formula for resizing.

Mayayana:

http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this
image. Depending on the software and level of
zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm
door with a screen in it. There's a pattern of hill-
shaped lines, alternating darker and lighter. That's
the actual image. But at some zooms it also shows
what looks like a shadow of the screen on the snow,
or dark lines coming from the lower left and swooping
up. I can't think how it could be happening, since
the image pixel data is not changed. Maybe the
combination of patterns is somehow distorting the
resizing algorythm? I've never seen anything like it.

No fancy explanations needed. The moiré effects you are seeing are the
result of having made a photograph through a fine screen. Don't do
that.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

On 02/04/2015 10:05 AM, Davoud wrote:
Mayayana:

http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this
image. Depending on the software and level of
zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm
door with a screen in it. There's a pattern of hill-
shaped lines, alternating darker and lighter. That's
the actual image. But at some zooms it also shows
what looks like a shadow of the screen on the snow,
or dark lines coming from the lower left and swooping
up. I can't think how it could be happening, since
the image pixel data is not changed. Maybe the
combination of patterns is somehow distorting the
resizing algorythm? I've never seen anything like it.

No fancy explanations needed. The moiré effects you are seeing are the
result of having made a photograph through a fine screen. Don't do
that.



I already told him that.

On Wed, 04 Feb 2015 16:44:49 +1300, Eric Stevens
wrote:

On Tue, 3 Feb 2015 22:18:13 -0500, "Mayayana"
wrote:

http://www.jsware.net/Files2/snow-on-screen.jpg

I'm wondering what might be going on with this
image. Depending on the software and level of
zoom it seems to show something like moire
patterns. The image is of snow stuck to a storm
door with a screen in it. There's a pattern of hill-
shaped lines, alternating darker and lighter. That's
the actual image. But at some zooms it also shows
what looks like a shadow of the screen on the snow,
or dark lines coming from the lower left and swooping
up. I can't think how it could be happening, since
the image pixel data is not changed. Maybe the
combination of patterns is somehow distorting the
resizing algorythm? I've never seen anything like it.


Separate snow falls? Even though snow may fall continually it may not
be faling constantly.

KK,it's Moire. Wha fooled me is th I have seen layers of snow looking
exactly like this behind a solid wood (emergency escape!) door at the
top of Mount Pilatus in Switzerland.
--

Regards,

Eric Stevens