diff --git a/res-hdpi/images/erasing_text.png b/res-hdpi/images/erasing_text.png
index 6138a4e..2186c19 100644
--- a/res-hdpi/images/erasing_text.png
+++ b/res-hdpi/images/erasing_text.png
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diff --git a/res-hdpi/images/error_text.png b/res-hdpi/images/error_text.png
index 722faaa..9700f45 100644
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diff --git a/res-hdpi/images/installing_security_text.png b/res-hdpi/images/installing_security_text.png
index 20d8ee2..0f60595 100644
--- a/res-hdpi/images/installing_security_text.png
+++ b/res-hdpi/images/installing_security_text.png
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diff --git a/res-hdpi/images/installing_text.png b/res-hdpi/images/installing_text.png
index cda9e02..ec8b875 100644
--- a/res-hdpi/images/installing_text.png
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diff --git a/res-hdpi/images/no_command_text.png b/res-hdpi/images/no_command_text.png
index d24f561..3eddcbb 100644
--- a/res-hdpi/images/no_command_text.png
+++ b/res-hdpi/images/no_command_text.png
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diff --git a/res-mdpi/images/erasing_text.png b/res-mdpi/images/erasing_text.png
index 659d49f..b0dd3c6 100644
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diff --git a/res-mdpi/images/error_text.png b/res-mdpi/images/error_text.png
index 4233358..6a47a59 100644
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+++ b/res-mdpi/images/error_text.png
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diff --git a/res-mdpi/images/installing_security_text.png b/res-mdpi/images/installing_security_text.png
index cde927a..1499398 100644
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+++ b/res-mdpi/images/installing_security_text.png
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diff --git a/res-mdpi/images/installing_text.png b/res-mdpi/images/installing_text.png
index 6c32857..01e9bfe 100644
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diff --git a/res-mdpi/images/no_command_text.png b/res-mdpi/images/no_command_text.png
index 0eba5c8..d340df5 100644
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diff --git a/res-xhdpi/images/erasing_text.png b/res-xhdpi/images/erasing_text.png
index 4c5d85d..2f8b469 100644
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diff --git a/res-xhdpi/images/error_text.png b/res-xhdpi/images/error_text.png
index f1e8c39..ad18851 100644
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+++ b/res-xhdpi/images/error_text.png
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diff --git a/res-xhdpi/images/installing_security_text.png b/res-xhdpi/images/installing_security_text.png
index a6580c8..acc6a7c 100644
--- a/res-xhdpi/images/installing_security_text.png
+++ b/res-xhdpi/images/installing_security_text.png
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diff --git a/res-xhdpi/images/installing_text.png b/res-xhdpi/images/installing_text.png
index dcfdbb2..32897d0 100644
--- a/res-xhdpi/images/installing_text.png
+++ b/res-xhdpi/images/installing_text.png
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diff --git a/res-xhdpi/images/no_command_text.png b/res-xhdpi/images/no_command_text.png
index 0c1b237..eb43c59 100644
--- a/res-xhdpi/images/no_command_text.png
+++ b/res-xhdpi/images/no_command_text.png
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diff --git a/res-xxhdpi/images/erasing_text.png b/res-xxhdpi/images/erasing_text.png
index 56421b6..8ff2b2f 100644
--- a/res-xxhdpi/images/erasing_text.png
+++ b/res-xxhdpi/images/erasing_text.png
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diff --git a/res-xxhdpi/images/error_text.png b/res-xxhdpi/images/error_text.png
index c121b2f..658d4ea 100644
--- a/res-xxhdpi/images/error_text.png
+++ b/res-xxhdpi/images/error_text.png
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diff --git a/res-xxhdpi/images/installing_security_text.png b/res-xxhdpi/images/installing_security_text.png
index ecbdaac..23fcaa4 100644
--- a/res-xxhdpi/images/installing_security_text.png
+++ b/res-xxhdpi/images/installing_security_text.png
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diff --git a/res-xxhdpi/images/installing_text.png b/res-xxhdpi/images/installing_text.png
index 93fbe73..fd8e584 100644
--- a/res-xxhdpi/images/installing_text.png
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diff --git a/res-xxhdpi/images/no_command_text.png b/res-xxhdpi/images/no_command_text.png
index 647e154..23932d6 100644
--- a/res-xxhdpi/images/no_command_text.png
+++ b/res-xxhdpi/images/no_command_text.png
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diff --git a/res-xxxhdpi/images/erasing_text.png b/res-xxxhdpi/images/erasing_text.png
index 853c6b1..0315293 100644
--- a/res-xxxhdpi/images/erasing_text.png
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diff --git a/res-xxxhdpi/images/error_text.png b/res-xxxhdpi/images/error_text.png
index fb18704..dba127f 100644
--- a/res-xxxhdpi/images/error_text.png
+++ b/res-xxxhdpi/images/error_text.png
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diff --git a/res-xxxhdpi/images/installing_security_text.png b/res-xxxhdpi/images/installing_security_text.png
index 2e911b2..6cdbef4 100644
--- a/res-xxxhdpi/images/installing_security_text.png
+++ b/res-xxxhdpi/images/installing_security_text.png
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diff --git a/res-xxxhdpi/images/installing_text.png b/res-xxxhdpi/images/installing_text.png
index cf0f833..32511a9 100644
--- a/res-xxxhdpi/images/installing_text.png
+++ b/res-xxxhdpi/images/installing_text.png
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diff --git a/res-xxxhdpi/images/no_command_text.png b/res-xxxhdpi/images/no_command_text.png
index 7b71b04..b6cdd77 100644
--- a/res-xxxhdpi/images/no_command_text.png
+++ b/res-xxxhdpi/images/no_command_text.png
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diff --git a/tools/recovery_l10n/README.md b/tools/recovery_l10n/README.md
index bf41ff2..1554f66 100644
--- a/tools/recovery_l10n/README.md
+++ b/tools/recovery_l10n/README.md
@@ -25,6 +25,8 @@
     *   "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.