Stephan Paukner :: syslog

Eric Brasseur explained a “bug” in the scaling algorithm of current image processing software. It’s not really a bug, technically, or mathematically. Calculating the numerical average of the surroundings of a pixel as the new color value is a pretty correct approach to scale an image down—if it’s seen as a data matrix. Rather, it’s visually not the thing you’d expect.

Technically speaking, the problem is that “the computations are performed as if the scale of brightnesses was linear while in fact it is an exponential scale.” In mathematical terms: “a gamma of 1.0 is assumed while it is 2.2.”

Here’s an example of what might occur:

The wrong way:

1. Take this image as a start:
   
2. Simply scale it down to 50%:
   

Obviously, this might not be what you intended.

The right way:

... you have an electronic hacker in your neighborhood. I bought the cheap Chinese solar USB charger revolt “4 Seasons” and wanted to use it to charge my Motorola Milestone/Droid or other devices while travelling by train or bike or during a hike. Unfortunately, it only provided power to “dumb” devices like not-so-smart phones or USB On-The-Go hard disks. When I connected it to my Milestone, the phone didn’t jump to the charging state. WTF? It turned out that modern smartphones like Milestone/Droid or iPhone rely on a properly implemented USB standard, what means that it’s not enough that the two outermost USB pins carry the needed voltage, but the inner pins must also provide a minimal “data voltage”. The problem is described here, and here is a DIY solution.

Thanks go to my work mate Wolfi for hacking the solar charger successfully.