On 3/02/2016 11:32, Chris Sherlock wrote:
On 3 Feb 2016, at 7:24 PM, SOS <s...@pmg.be> wrote:
On 3/02/2016 3:55, Kohei Yoshida wrote:
On Wed, 2016-02-03 at 10:52 +1100, Chris Sherlock wrote:
The other question is: why would we not want to the actual DPI and
screen resolution?
My understanding is that, historically, the OS provided a function to
query DPI but what gets returned from such function was not always
accurate (or always not accurate depending on who you ask). So, the
workaround at the time was to assume that DPI is always 96 (and
hard-code that value) regardless of what the OS told you, which worked
just fine because the monitors used back in the day had the same screen
resolution.
Mostly DPI is found in the header of a pixelfile (taken by camera).
Unfortunately it's not the photographer who gets to decide about the needed DPI.
DPI is actually a wrong definition for documents, Dots Per Inch is a definition
used by output devices. Screens need a PIXEL par DOT but for print devices
there is no precise correlation between the number of dots used by the device
and the pixels needed in the image for having a maximum image-view quality.
The print industry has come to some standards by trial and error.
- monitor screens need 96 - (220-retina) pixels per inch
- laser printers need 150 pixels per inch (up tot 2000 + dots)
- offset printers need 254 -300 pixels per inch (up to 3000 dots)
Definitely true :-) Only in OS X’s case, it doesn’t actually report back the
correct resolution unless you ask for the backing coordinate system.
The PPI business is a red herring I think I’ve introduced into this discussion
I’m afraid. We calculate the PPI ourselves (and call it DPI) based on the
reported pixels, and the size of the screen in mm (which we obviously convert
to inches).
its a bit the wrong discussion: what we see on screen has no relevance:
the user can "zoom" the document until he is happy with the image
quality on screen
But in the current situation, LO users has no idea how big (size) he can
place a image in a document.
When the doc is intented for online use (email and Web) then there is a
minimum of 96 pixels par inch needed. More is no problem but is in many
cases a overkill.
Who is editing a "book" or a "magazine" need minimal 254 pixels par inch
to has a good image quality after printing.
When using less pixels the book pages are looking fine on screen put
shall have a creepy print quality
So having a new "DocumentProperty" indicating the needed pixels (for
printing) make it possible to make the "size" calculations before
inserting.
I guess I’m curious as to what is relying on the screen resolution and PPI.
Although… it’s funny that we have the function SalGraphics::GetResolution, but
that returns the PPI!
Chris
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