Android: drawable resolutions

I've been through this post (and others) as well as through the documentation about supporting different screen resolutions in Android, but I couldn't find a clear answer to a (simple) question:

Is it ok to just use "res/drawable" for images in an android app?

Background: The only images that are needed in this specific app are the app icon itself and an icon for a notification, there won't be any images in any layout.

So in my understanding, if no "hdpi"-, "mdpi"- and "ldpi"-folders are found, Android will use "res/drawable" as the fallback.

As the only pitfall with different screen-resolution seems to be that Android will scale images for a specific resolution if no special one is found, this should o开发者_StackOverflow社区nly be a problem when UPscaling, because the image will get blurry. But if I provide all "hdpi"-images in "res/drawable" (instead of 3 different ones), won't Android just DOWNscale those images if the size is too big?

If that's true, I could save some APK-space by just a third of the images.

Follow-Up question: I read that for API-level 3 a dir by the name "drawable-v3" is required. Is that true or is "drawable" the fallback for this API-level also?

Any hint is appreciated.

The images in the drawables folder are assumed to be at mdpi resolution, so they will get scaled up/down if you don't provide the others.

Scaled up images will be low-resolution and look fuzzy. Scaled down images will have pixels missing and look jaggy.

So your app will "work" with only one set of default images, but will look awful on many devices. I strongly advise that you create the images in different sizes, so it looks great on all devices - it's a bit boring, but not hard to do.

It won't be long before we have xhdpi devices, so while you're at it you may want to create those too.

I assume you've read this

Not a complete answer, but: highly downscaled images can and usually do look just as bad as upscaled images (but in a different way), because graphics libraries almost exclusively use interpolation methods for resizing, and interpolation methods are limited in terms of how much they can shrink an image before serious information loss (to about 50% for linear methods and down to about 25% for bicubic methods). This is why most platforms have evolved conventions (like hdpi, mdpi etc.) that let you embed images that are best for each screen size.

I use drawable/ all the time, and then I go to BestBuy and all the local wireless stores and test my apps on small/large/huge(tablet) devices and they look just fine.

Unless you have some reason to target pre-Donut devices (now only 4% of the devices according to http://developer.android.com/resources/dashboard/platform-versions.html), then you should put your bitmaps in one of the -Xdpi directories. The generic "drawable" directory is a synonym of "drawable-mdpi" for compatibility reasons, but a modern well-written app should be putting its drawables in a directory matching the density they are designed for.

res/drawable is the fallback

the caveat is that scaling not only degrades the image but takes processing time too.

I have not even read the API-Level 3 docs yet, sorry for 1/2 an answer

For what it is worth I found the image handling of Android to be tedious and unreliable. The concept of including different size images for different screens will result in large application files bloated with images. There are already screens that don't fit in the standard resolution ranges. I have found it is best not to let android handle the scaling, it seems to create a base image for the smallest screen you target and then scale it up resulting in ordinary looking images on large screens. This happens even if you made the image specifically for the large screen. My solution that seems to work on everything from a 2" samsung phone to a Sony Tablet is to create images at high resolution and use Bitmap.createScaledBitmap() to get the size I need.

caveat: I am new to Android and have lots to learn.