Disable Android resource / image / PNG optimizatio

问题:

How do I prevent the Android "build process" from optimizing .png images?

I have an Android project with the following res directories:

- /res/
- /res/drawable
- /res/drawable-hdpi
- /res/drawable-hdpi-v5
- /res/drawable-ldpi
- /res/drawable-ldpi-v5
- /res/drawable-mdpi
- /res/drawable-mdpi-v5

These directories contain many .png files. I optimize PNG sizes with PNGOUTWin, and the overall size is reduced by more than 20%. When I build the .apk file, the images are "optimized" by the build process and the overall size is now 10% above the initial size, or 30% above my/PNGOUTWin optimized size.

My goal is to reduce the .apk size, even if it will affect the final performance, memory requirements, etc. How do I prevent the "build process" from optimizing .png images?

I'm targeting Android 2.2 and above.

P.S.: I am currently building my Android project from Eclipse, but I will switch to the automated build later (Ant?).

Note about JPG images: JPG will not work, because they do not have transparency.

回答1:

As mentioned in the Android documentation: http://developer.android.com/guide/topics/graphics/2d-graphics.html#drawables

Note: Image resources placed in res/drawable/ may be automatically optimized with lossless image compression by the aapt tool during the build process. For example, a true-color PNG that does not require more than 256 colors may be converted to an 8-bit PNG with a color palette. This will result in an image of equal quality but which requires less memory. So be aware that the image binaries placed in this directory can change during the build.

So if you want to reduce the size of your application you should either reduce the color-depth of your PNG files (this helps a lot) or switch to .JPG files wherever possible.

回答2:

Finally there is an official way to disable the PNG cruncher with Gradle which hasn't been mentioned here yet:

1. Edit main build.gradle to require gradle version 1.1.3 (or newer):

   buildscript {  
       repositories {  
           mavenCentral()  
       }  
       dependencies {  
           classpath 'com.android.tools.build:gradle:1.1.3'  
       }  
   }  
   

2. In the individual apps's build.gradle, section android {}, insert:

   aaptOptions {  
       cruncherEnabled = false  
   }  
   

Reference: https://code.google.com/p/android/issues/detail?id=65335

回答3:

Specifying PNG crunching is now a BuildType property and is disabled by default on debug builds:

android {
    …
    buildTypes {
        release {
            crunchPngs false // or true
        }
    }
}

Note: It's available from Android Studio 3.0 Canary 5 .

回答4:

Android Studio: Since Gradle Android plugin 1.0.0:

android {
...
  aaptOptions {
    useNewCruncher false
  }
....
}

Eclipse: Override the crunch task writing this in your build.xml:

<target name="-crunch">
   <echo message="This will skip PNG optimization"/>
</target>

回答5:

Google recently introduced a new PNG processor in aapt 0.9.1 in the Android SDK Build Tools that fixes this issue of increased PNG sizes after aapt optimization.

With this update, it is now possible for Android Studio & Gradle to switch between the PNG processors with the following change in your build.gradle configuration file:

android {
    ..
    ..

    aaptOptions.useAaptPngCruncher = false
}

By adding this line, aapt uses the new PNG processor in which it checks to see if the "optimized" PNG files are smaller than the original PNG files. I was able to reduce 4.8 MB in my compiled APK and have not encountered any bugs/issues with the new build configuration.

UPDATE: This has been deprecated in later versions of Android Studio. Please refer to the answer provided by ChrisG.