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I am designing an app for multiple screen sizes in Android and I have been researching a lot on how the sizes should be kept. Until now I have been able to understand that for multiple sizes such as ldpi, mdpi, hdpi, xhdpi we need to give elements for all of them. But I am confused on this issue:

Suppose I make a design on 6 inch screen with 480 dpi to make the elements look crisp ans clear. If I need the same design I'll change the dpi value to 160 if I want to design for a 3 inch phone. So if I decrease the dpi my resolution also decreases, right?

And what if I want the resolution to be same but the value of dpi to decrease or increase. How do I do that? (I know how to do it in Photoshop but I tried and checked it hardly make a difference)

Can two different resolutions fit one screen size with different dpi values, as done in retina displays? How does it happen ?

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Here's the best explanation I've read on what DPI actually means:.

The short version: If you change the DPI of an image it has no effect on the quality of that image. DPI is only relevant in the context of an output device like a printer. On screens, it has no effect.

A 1,000×1,000 pixel image file will have the same quality and amount of information regardless of it's DPI setting. It'll be exactly 1,000,000 pixels no matter what.

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Pixels is really your stable datum, inches and dpi just makes it easier to think with. You can change your dpi and leave your size alone if you want, but as far as I can tell, that won't make any difference in how it shows on the device. A 1 inch 300 pixel, will show exactly the same size as 2 inch 150 pixel image.

What determines how big it is on the screen is dependent on the resolution of the screen. (from what I can tell)

Hope that helps.

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As stated, people should simply ignore the DPI when designing for electronic devices.

When designing an app try to do things right.

  1. Leave icons and graphic elements. Either something like a font-icon or directly as SVG. This will give you a resolution-independent asset.

  2. There are several approaches when using photos.

a. Using the declared total pixels. You can use a website like http://whatismyscreenresolution.net/ to get it.

  • And on top of that, you can make the famous 2x or 3x assets to replace them.

b. You can just use one asset. The most common resolution on mobile devices is on 2019 is full HD. Just use 1080x1920 px as your maximum size, or as maximum with or height.


The approach depends on what the images are for. Is it a gallery? will the gallery have a zoom option? Is it a background? Do I really need detail? Do I want to save bandwidth?

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"DPI" usually refers to dots of ink printed on paper, but in the context of what you are talking about, "dpi" refers to the density of phosphor elements on various phone displays. Not all screens are the same, and some larger displays may actually be smaller in pixel dimension than a physically smaller, yet higher density display. None of this is really worth worrying about though from the perspective of designing for screens.

All you really need to know is the actual pixel dimensions needed per target device.

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