[CREATE] [Mypaint-discuss] Resolution information in ORA

Andrew Chadwick a.t.chadwick at gmail.com
Wed Feb 26 16:23:10 PST 2014

Interesting, but a bit of a moot point. I've already updated the
standard with 72ppi as the default for apps which care about
resolution when loading ORA files where resolution info is
*unspecified*. What does "unspecified" mean? Well, either

1. The app that wrote the data doesn't use resolution information at
all, for anything. With a pixel-based format, this is perfectly OK.


2. The app does care about it, but not enough to declare what
resolution it used internally. Lazy app! That's broken behaviour now,
and shouldn't happen. If an app writes anything into the ORA file that
needs resolution info, like a text object set in "90pt Sans", it
*really, really should* write its typesetting ppi into xres.


3. The app that wrote the data is a pre-OpenRaster-0.0.3 application. Ahem.

Understand that the 72ppi is there merely as a safe (but stupid)
fallback for broken and legacy cases that an app might have to deal

Apps are free to create *new* OpenRaster files which use sensible
print resolutions, or the user's real monitor resolution, or some
hardcoded default of their own. They're also free to substitute higher
resolutions for a "default" 72ppi if no object within the OpenRaster
file had need of resolution info, but that feels like cheating
somehow! Anyway,

* Is that enough?

* Do we need an extra sentence or two in there saying that a) apps
*must* populate xres and yres if they write *any* data into the ORA
file with non-pixel sizes, or b) that 300ppi is a Very Good Idea these
days ?

And if enough people both disagree with 72ppi as the fallback, we can
of course change it - provided everyone also agrees on what the new
standard should be!

On 26 February 2014 22:14, Gez <listas at ohweb.com.ar> wrote:
> El mié, 26-02-2014 a las 17:05 +0000, Andrew Chadwick escribió:
>> Ah yes. 72, my mistake. That's the ubiquitous default, and there are
>> presumably reasons for its ubiquity.
> http://www.photoshopessentials.com/essentials/the-72-ppi-web-resolution-myth/
> It's just an inherited default. The resolution only matters for physical
> representations.
> Since our monitors will show pixels at 1:1 ratio, the resolution of the
> file won't matter for screens, unless the program offers a feature to
> simulate the real-world size on screen, like GIMP does (but you need to
> set your screen's resolution properly to make it work anyway).
> Screen resolutions are moving targets. For instance, an old 17 inch CRT
> monitor displaying 1280x1024 has more resolution than a large HD TV
> set. :-)
> There isn't a standard screen resolution. You have to know the physical
> size of the screen and the how many pixels it shows.
> And since resolution will matter mainly for printed outputs, I think it
> would be better to default to a print standard instead of an obsolete
> "screen" resolution.
> When people want to print their artwork, they expect a good quality
> print, not a pixelated blob (and that's what you get printing at 72 dpi)
> 300 dpi is a standard for professional print and a reasonable resolution
> for high quality print in home/office printers.
> If a default value has to be set, I think that a value that provides
> good quality prints would be an improvement over the good ol' 72dpi.
> Gez.
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Andrew Chadwick

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