我如何从高分辨率图像android获取所有dpi图像

Question

I'am a new android developer.

Our designer gave me some high resolution images for my app, but I known there are many devices (different screens) that support the android platform.

My question is. How can I get all the dpi(hdpi-mdpi-ldpi-xx) resources from the high resolution images?

Answer 1

如果我得到你的问题，这里是解决方案:) http://coh.io/adpi/

Answer 2

Just add all your images on the xhdpi folder and Android will find them recursively through the folders until it found the requested photo independently from from the devices screen density.

From the documentation:

At runtime, the system ensures the best possible display on the current screen with the following procedure for any given resource:

1. The system uses the appropriate alternative resource Based on the size and density of the current screen, the system uses any size- and density-specific resource provided in your application. For example, if the device has a high-density screen and the application requests a drawable resource, the system looks for a drawable resource directory that best matches the device configuration. Depending on the other alternative resources available, a resource directory with the hdpi qualifier (such as drawable-hdpi/) might be the best match, so the system uses the drawable resource from this directory.

2. If no matching resource is available, the system uses the default resource and scales it up or down as needed to match the current screen size and density The "default" resources are those that are not tagged with a configuration qualifier. For example, the resources in drawable/ are the default drawable resources. The system assumes that default resources are designed for the baseline screen size and density, which is a normal screen size and a medium density. As such, the system scales default density resources up for high-density screens and down for low-density screens, as appropriate. However, when the system is looking for a density-specific resource and does not find it in the density-specific directory, it won't always use the default resources. The system may instead use one of the other density-specific resources in order to provide better results when scaling. For example, when looking for a low-density resource and it is not available, the system prefers to scale-down the high-density version of the resource, because the system can easily scale a high-density resource down to low-density by a factor of 0.5, with fewer artifacts, compared to scaling a medium-density resource by a factor of 0.75. For more information about how Android selects alternative resources by matching configuration qualifiers to the device configuration, read How Android Finds the Best-matching Resource.

Either way for getting the other resources if you want to follow good practices, this are the ratios to scale your hdpi resources to lower densities.

Hope it helps :)

Answer 3

you can convert them and create the appropriate images for each resolution using the link @karvoynistas posted and this would also be a must read.

Notice that you don't really need to do anything if you want to let your images being resized automatically... (you can define only one folder and let the system resize them. Pros: your app would weight less. Cons: it may be slower and you may have problems of memory with large images due to a limited heap size...)