Apply multiple fixes to autopkgtests

Closes: #1079025

debian/tests/compare

@@ -12,6 +12,13 @@ sudo systemctl start xrdp
 # login screen.
 xvfb-run -l "$testdir/connect-and-capture" "$screenshot"
 
+# Try to remove the background to leave just the login window in the image
+cp -a "$screenshot" "${screenshot}.before.mogrify.png"
+mogrify -fuzz 4% -define trim:percent-background=0% -trim +repage -format png "$screenshot"
+
+# Resize the search image to match nearly the really displayed size
+convert -resize 50% /usr/share/xrdp/xrdp_logo.bmp xrdp_logo_50percent.png
+
 # Confirm that the XRDP logo is in the log in screen (so as to confirm that the
 # login screen is really there).
 # https://stackoverflow.com/questions/31867093/how-to-search-an-image-for-subimages-using-linux-console
@@ -21,7 +28,7 @@ xvfb-run -l "$testdir/connect-and-capture" "$screenshot"
 # will fail but we don't need to check that specifically, because so
 # will the if below.
 compare -metric RMSE -subimage-search \
-  "$screenshot" /usr/share/xrdp/xrdp_logo.bmp png:"$magickout"
+  "$screenshot" xrdp_logo_50percent.png png:"$magickout"
 # In case of match, output will be like
 # "520,347: (255,255,255)  #FFFFFF  gray(255)"
 # in which the first field is the coordinates of the match.

debian/tests/connect-and-capture

@@ -1,4 +1,4 @@
 #!/bin/sh
-xfreerdp /f /v:localhost:3389 /p: /u: /d: &
+xfreerdp /f /v:localhost:3389 /p: /u: /d: /cert-tofu &
 sleep 12
 import -window root "$1"