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+# Steps to regenerate background text images under res-*dpi/images/
+
+1.  Build the recovery_l10n app:
+
+    cd bootable/recovery && mma -j32
+
+2.  Install the app on the device (or emulator) with the intended dpi.
+
+    *   For example, we can use Nexus 5 to generate the text images under
+        res-xxhdpi.
+    *   We can set up the maximum width of the final png image in res/layout/main.xml
+        Currently, the image width is 1200px for xxxhdpi, 900px for xxhdpi and
+        480px for xhdpi/hdpi/mdpi.
+    *   When using the emulator, make sure the NDK version matches the current
+        repository. Otherwise, the app may not work properly.
+
+    adb install $PATH_TO_APP
+
+3.  Run the app, select the string to translate and press the 'go' button.
+
+4.  After the app goes through the strings for all locales, pull the output png
+    file from the device.
+
+    adb root && adb pull /data/data/com.android.recovery_l10n/files/text-out.png
+
+5.  Compress the output file put it under the corresponding directory.
+
+    *   "pngcrush -c 0 ..." converts "text-out.png" into a 1-channel image,
+        which is accepted by Recovery. This also compresses the image file by
+        ~60%.
+    *   zopflipng could further compress the png files by ~10%, more details
+        in https://github.com/google/zopfli/blob/master/README.zopflipng
+    *   If you're using other png compression tools, make sure the final text
+        image works by running graphic tests under the recovery mode.
+
+    pngcrush -c 0 text-out.png $OUTPUT_PNG