why matlab calls (pixel per inch "PPI") a (dot per inch "DPI") ?

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Osama Alkurdi 2021-2-23

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https://ww2.mathworks.cn/matlabcentral/answers/753629-why-matlab-calls-pixel-per-inch-ppi-a-dot-per-inch-dpi

评论： Walter Roberson 2021-2-23

采纳的回答： Walter Roberson

why matlab uses the DPI abbreviation for a something called the screen pixels per inch unit,

the DPI term indicates to a something related to printing terminology which is dot ink per inch unit,

is it a mistake or there is an explaination for this?

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Bjorn Gustavsson 2021-2-23

I'm happy enough to work predominantly on Linux-systems, so I get the resolution "determined by your system resolution"...

...I will not be forward enough to tell you what to do with regards to this, but I'm happy with my choise.

Osama Alkurdi 2021-2-23

编辑：Osama Alkurdi 2021-2-23

ok thats not helping me :(, and what is "system resolution" mean, i found the sentence misleading, do they mean you can specify your dpi at linux and matlab works with that value, and if so how you can change something fixed like dpi which depends on number on pixels which is constant and and screen dimensions which is also constant.

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Answer 1

Walter Roberson 2021-2-23

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the DPI term indicates to a something related to printing terminology which is dot ink per inch unit,

Although it did certainly have that meaning, historically most electronic displays were CRT (Cathode Ray Tubes), and historically those used round-ish pixels created by steering an electron beam, so historically it was dots per inch for displays.

Technology for displays now varies quite a bit. Quite a lot of the technologies use dots of various forms. There are not a lot of display technologies around for which "dot" is technically wrong.

Dots Per Inch is mostly used to refer to physical limitations, whereas Pixels Per Inch is mostly used to refer to logical arrangements. For example my physical display is normally 2560 x 1440, but I can configure it for 1600 x 900 pixels per inch, with the graphics card automatically scaling . As that is a 1.6 ratio, the implication is that the hardware might have subpixels that are not user addressible. Hypothetically individual sub-pixels on the hardware might not have enough brightness or clarity, or there might be too much leak between adjacent wells to make the sub-pixels useful, but having the same level going to multiple sub-pixels in an area might overcome those problems, allowing a variety of pixel sizels (visible units) to be overlayed on hardware dots.

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Osama Alkurdi 2021-2-23

thats not helping me :(, i am so confused.

Walter Roberson 2021-2-23

A) It is not a mistake.

B) The explanation is at https://www.mathworks.com/help/matlab/creating_guis/dpi-aware-behavior-in-matlab.html

C) Using "DPI" is technically correct in most hardware situations. It is not always true, but you are unlikely to be using a retro-computing Tektronix 4014 https://en.wikipedia.org/wiki/Tektronix_4010 (early 1980s) or one of the highly specialized displays they use for radar tracking. (At one point in early 1980s I was part of an airplane tracking software team, but I was never permitted near a real tracking system, only a mock-up.)

D) "DPI" usually refers more to hardware, and PPI (Pixels Per Inch) usually refers more to logical resolutions overlayed on hardware

E) The reasons for taking this approach is that even as resolutions increase, people need pretty much fixed-physical-width text, and trying to mix angular resolutions (readability) with plots and images (which can often do nicely with same number of denser pixels => smaller physical size) is messy. https://www.mathworks.com/matlabcentral/answers/753864-matlab-gives-wrong-graphical-display-info#comment_1349719

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