Determining image sizes for multiple android screen sizes/densities

I've been reviewing the Supporting Multiple Screens documentation on the Android and I just need some additional clarification...

It's my understanding that designing three unique interfaces (ldpi, mdpi, and hdpi) would be the best way to go about supporting all the potential android screens with minimal scaling/distortion.

Yes, I know there are similar questions posted, however... If I create an image for the benchmark mdpi (let's say my image is 300x210, just for exampl开发者_运维知识库e) how to I determine what size I will need to recreate that image at ldpi & hdpi? This post as well as a google search leads me to believe that ldpi is just 75% of the mdpi image, and the hdpi is 150% of the mdpi image. Is this accurate?

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-ldpi is ~120dpi, -mdpi is ~160dpi, -hdpi is ~240dpi.

So, a 320px wide image is 2" in -mdpi. If you want a 2" image on -ldpi, you want it to be 240px (=75% of original). If you want a 2" picture on -hdpi, you need 480px (=150% of original).

Hence, your analysis is accurate.