[OSM-talk] Attribution guideline update

[Michal Migurski]

> On Feb 19, 2020, at 5:29 AM, Martin Koppenhoefer <dieterdreist at gmail.com> wrote:
> 
> I am not sure what "device-independent pixels" means. Is this about points (i.e. physical, hardware screen pixels divided by the scale)? IMHO we should require actual, physical pixels, because it is them who determine whether the attribution string will be readable --- and the requirement should be tougher. We have seen many examples of easily readable, unobtrusive attribution on much smaller maps. For example the osm.org <http://osm.org/> website on 467 pixels wide has room for a scale bar and this text: "© OpenStreetMap contributors # Make a Donation. Website and API terms" in a single line.
> 
> The actual requirement for "© OpenStreetMap contributors" is around 163 pixels. My suggestion would be to make this half: 250 pixels, maybe even less like 200 (theoretical) pixels for retina screens (i.e. 400 actual pixels on retina at 2x and 600 actual pixels on retina at 3x).
> Our goal is not to avoid attribution but to show it when it can reasonably be done.

Device-independent pixels are a concept used in CSS in response to the high-resolution screens available for the past few years. Since actual, physical pixels are now very small, a new definition expresses them in terms of visual angle so that pixel-defined CSS layouts from the past few decades aren’t suddenly illegible: “By definition, this is the physical size of a single pixel at a pixel density of 96 DPI, located an arm's length away from the viewer's eyes.”

https://developer.mozilla.org/en-US/docs/Glossary/CSS_pixel

For our purposes, this is a better definition because it’s defined in terms of what a viewer can see rather than its implementation in hardware.

-mike.
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