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androiddrawablescreen-resolution

Why provide multiple drawables for various densities?

My app supports various screen densities from ldpi to xhdpi. It contains some drawables (images) that need to be displayed properly on all densities. I'm wondering how many various resolutions of the drawables are actually necessary to provide, considering that Android runtime is scaling resources when it cannot find one for the appropriate density.

If you provide only mdpi drawables, they will be scaled up on hdpi/xhdpi (blurry) and scaled down on ldpi screen.

However, if you provide only xhdi resources, then they will be scaled down on all lower density screens. Scaling down doesn't make them blurry and they will look fine.

So why bother providing drawables for other densities than xhdpi?

Solution

  • There are several reasons to used prescaled drawables:

    1. Scaling down to lower resolutions takes resources (CPU time, memory and it drains your battery faster), especially if you have a lot of images this might be undesired.

    2. Scaling down a large image might result in worse quality than using a 'pre-tuned' smaller image. Especially if your images are based on a vector original. Or they contain very fine lines or details, which will get lost when due to the scaling.
      For example:
      original image becomes scaled image
      See here for the source of these images and more information on scaling artifacts.

    3. On lower resolutions the image pixels are larger (or the image gets smaller), so it might be required to remove certain aspects of the image to keep it clear/understandable.