diff --git a/Makefile b/Makefile
index 23da149d76a1..6affeee38d95 100644
--- a/Makefile
+++ b/Makefile
@@ -427,16 +427,17 @@ generate-images:
 	inkscape -f $(PWD)/assets/logo.svg -w 32 -h 32 -jC -i layer2 -e $(TMPDIR)/images/32-2.png
 	composite -compose atop $(TMPDIR)/images/32-2.png $(TMPDIR)/images/32-1.png $(TMPDIR)/images/32-raw.png
 	inkscape -f $(PWD)/assets/logo.svg -w 16 -h 16 -jC -i layer1 -e $(TMPDIR)/images/16-raw.png
-	zopflipng $(TMPDIR)/images/128-raw.png $(TMPDIR)/images/128.png
-	zopflipng $(TMPDIR)/images/64-raw.png $(TMPDIR)/images/64.png
-	zopflipng $(TMPDIR)/images/32-raw.png $(TMPDIR)/images/32.png
-	zopflipng $(TMPDIR)/images/16-raw.png $(TMPDIR)/images/16.png
+	zopflipng -m -y $(TMPDIR)/images/128-raw.png $(TMPDIR)/images/128.png
+	zopflipng -m -y $(TMPDIR)/images/64-raw.png $(TMPDIR)/images/64.png
+	zopflipng -m -y $(TMPDIR)/images/32-raw.png $(TMPDIR)/images/32.png
+	zopflipng -m -y $(TMPDIR)/images/16-raw.png $(TMPDIR)/images/16.png
 	rm -f $(TMPDIR)/images/*-*.png
 	convert $(TMPDIR)/images/16.png $(TMPDIR)/images/32.png \
 					$(TMPDIR)/images/64.png $(TMPDIR)/images/128.png \
 					$(PWD)/public/img/favicon.ico
 	rm -rf $(TMPDIR)/images
-	
+	$(foreach file, $(shell find public/img -type f -name '*.png'),zopflipng -m -y $(file) $(file);)
+
 .PHONY: pr
 pr:
 	$(GO) run contrib/pr/checkout.go $(PR)
diff --git a/public/img/auth/dropbox.png b/public/img/auth/dropbox.png
index da2348872a06..c2f4c90974a6 100644
Binary files a/public/img/auth/dropbox.png and b/public/img/auth/dropbox.png differ
diff --git a/public/img/auth/facebook.png b/public/img/auth/facebook.png
index 29273af14fb0..80aa5183acb9 100644
Binary files a/public/img/auth/facebook.png and b/public/img/auth/facebook.png differ
diff --git a/public/img/auth/google_plus.png b/public/img/auth/google_plus.png
index 720824230a50..21251288d271 100644
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diff --git a/public/img/auth/openid_connect.png b/public/img/auth/openid_connect.png
index af033cd1fe12..3d0de52e4e4a 100644
Binary files a/public/img/auth/openid_connect.png and b/public/img/auth/openid_connect.png differ
diff --git a/public/img/auth/twitter.png b/public/img/auth/twitter.png
index a4f14de57ae4..9d3d89a4af14 100644
Binary files a/public/img/auth/twitter.png and b/public/img/auth/twitter.png differ
diff --git a/public/img/avatar_default.png b/public/img/avatar_default.png
index 30aca2ef061f..455155db1042 100644
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diff --git a/public/img/favicon.ico b/public/img/favicon.ico
index fd35f5357fdd..681d76d33ac3 100644
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diff --git a/public/img/favicon.png b/public/img/favicon.png
index 48169c1b683c..30d331359463 100644
Binary files a/public/img/favicon.png and b/public/img/favicon.png differ
diff --git a/public/img/gitea-192.png b/public/img/gitea-192.png
index 63f963e846a9..12caba8d5ddf 100644
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diff --git a/public/img/gitea-512.png b/public/img/gitea-512.png
index 59d1fed7d976..456abfa0c0aa 100644
Binary files a/public/img/gitea-512.png and b/public/img/gitea-512.png differ
diff --git a/public/img/gitea-lg.png b/public/img/gitea-lg.png
index 1538cd1852b7..682ceaf7bed8 100644
Binary files a/public/img/gitea-lg.png and b/public/img/gitea-lg.png differ
diff --git a/public/img/gitea-sm.png b/public/img/gitea-sm.png
index 05922cdbc859..405f40f17099 100644
Binary files a/public/img/gitea-sm.png and b/public/img/gitea-sm.png differ
diff --git a/public/img/openid-16x16.png b/public/img/openid-16x16.png
index b3184808423b..ee1b00e147f4 100644
Binary files a/public/img/openid-16x16.png and b/public/img/openid-16x16.png differ
diff --git a/public/img/slack.png b/public/img/slack.png
index d61c2cd4e678..28d863f8cb0b 100644
Binary files a/public/img/slack.png and b/public/img/slack.png differ