joi, decembrie 23, 2010

miercuri, decembrie 22, 2010

What is dust?

Let's set aside the bunny for a second, and focus on the filth. Dust is everywhere. Fine sand is rock dust. Rubber, brakepad and pavement particles are road dust. Fine ash can be volcanic dust. Hell, Carl Sagan famously and repeatedly referred to Earth as a "mote of dust," albeit in a cosmic sense. But the dust we're talking about, dust bunny dust, is a specific thing, with a specific recipe. And a studied one! According to David W. Layton and Paloma I. Beamer, who coauthored a report called ‘Migration of Contaminated Soil and Airborne Particulates to Indoor Dust,' typical household dust in a midwestern home is comprised of the following:

Indoor dust is a mixture of soil tracked into a residence, particulate matter derived from ambient outdoor air, and importantly, organic matter inputs from various sources. A prominent feature of indoor dust is its organic material content, with levels of about 40 wt % in residential housing.

Tot articolul:

sâmbătă, decembrie 18, 2010

Frozen lighthouse

Google Streetview Romania

Vocea este foarte enervanta. Ce e relevant este ca au lansat Streetview in Romania. Interfata e mult mai buna ca la Norc dar pozele si acoperirea sunt mult mai slabe (90% Buc, restul oraselor doar strazile principale). In plus google a scanat doar un sens de mers si asta face greoaie observarea strazilor late si a bulevardelor.

Sa vedem cum vor evolua.

Thanks Cristi!

Analiza unei iluzii optice

Sanse mari sa mai fi vazut aceasta iluzie optica. "Culoarea albastra" si verde sunt aceeasi (anume RGB 0,255,150). Ce nu ati vazut este acest studiu interesant:

So what we see above is the same greenish blue region, touching the green on top and the blue on bottom — with no particular seams, implying (correctly) that there is no actual difference in color and what is detected is merely an illusion.

And the story would end there, if not for DanKam.  DanKam’s an augmented reality filter for the color blind, designed to make clear what colors are what.  Presumably, DanKam should see right through this illusion.  After all, whatever neurological bugs cause the confusion effect in the brain, certainly were not implemented in my code.

You might notice that while we’re recovering the color, or chroma relatively accurately, we’re losing detail in perceived luminance. Basically, we’re losing edges.

It’s almost like the visual system sees dark vs. light at a different resolution than one color vs. another.

This, of course, is no new discovery. Since the early days of color television, color information has been sent with lower detail than the black and white it augmented. And all effective compressed image formats tend to operate in something called YUV, which splits the normal Red, Green, and Blue into Black vs. White, Red vs. Green, and Orange vs. Blue (which happen to be the signals sent over the optic nerve). Once this is done, the Black and White channels are transmitted at full size while the differential color channels are halved or even quartered in detail. Why do this? Because the human visual system doesn’t really notice. (The modes are called 4:2:2 or 4:1:1, if you’re curious.)

So, my theory is that these color artifacts aren’t the result of some complex analysis with pattern matching, but rather the normal downsampling of chroma that occurs in the visual system. Usually, such downsampling doesn’t cause such dramatic shifts in color, but of course the purpose of an optical illusion is to exploit the corner cases of what we do or do not see.

Tot articolul (cu si mai multe exemple):

vineri, decembrie 10, 2010

duminică, decembrie 05, 2010

sâmbătă, decembrie 04, 2010

vineri, decembrie 03, 2010

Noul Yahoo mail beta

Ca sa il activati mergeti la pagina asta: si apasati "Try it now"

Singurul lucru care mi se pare mie relevant este ca noua interfata este mult mai rapida.