diff --git a/cropgui_common.py b/cropgui_common.py
index b931620..e8d090e 100755
--- a/cropgui_common.py
+++ b/cropgui_common.py
@@ -69,9 +69,16 @@ def get_cropspec(image, corners, rotation):
     t, l, r, b = corners
     w = r - l
     h = b - t
-    # Technically this should produce perfect crops, but jpegtran is broken
-    # and so mistakenly rounds out fractional crops on flipped images.  Sigh.
-    return "%dx%d+%d+%d" % (w, h, l, t)
+    # Technically these parameters should straightforwardly produce perfect
+    # crops, but jpegtran is broken here in two regards: (1) it doesn't
+    # recognise perfect rotated crops as such, so the '-perfect' switch
+    # erroneously rejects correctly ICMU-aligned rotate-and-crop commands, and
+    # (2) it mistakenly rounds out crops on rotated/flipped images so that even
+    # the bottom right corner is ICMU-aligned.  Sigh.  Adding the 'f' suffixes
+    # to the dimensions here at least solves (2), and seems to produce the same
+    # results as you get by manually constructing a pipeline of '-perfect'
+    # command lines.
+    return "%dfx%df+%d+%d" % (w, h, l, t)
 
 
 def ncpus():
diff --git a/generate_test_images.sh b/generate_test_images.sh
index 69964c3..9405248 100755
--- a/generate_test_images.sh
+++ b/generate_test_images.sh
@@ -5,11 +5,12 @@
 dir=test
 [ -d $dir ] || mkdir $dir
 
+text='-density 72 -pointsize 32 -weight Bold -gravity NorthWest -fill rgba(255,0,0,0.5) -annotate +0+0 A -annotate +32+32 B -annotate +64+64 C -annotate +96+96 D -annotate +128+128 E -annotate +160+160 F -annotate +192+192 G -annotate +224+224 H -annotate +256+256 I -annotate +288+288 J -annotate +320+320 K -fill rgba(0,255,0,0.5) -annotate +352+352 L -annotate +384+320 M -annotate +416+288 N -annotate +448+256 O -annotate +480+224 P -annotate +512+192 Q -annotate +544+160 R -annotate +576+128 S -annotate +608+96 T -annotate +640+64 U -annotate +672+32 V -fill rgba(0,0,255,0.5) -annotate +704+0 W -annotate +736+32 X -annotate +768+64 Y'
 convert -size 100x100 pattern:gray50 -scale 1600% -sampling-factor 2x2 \
-    -crop 796x396+0+0 $dir/chess-2x2.jpg
+    -crop 796x396+0+0 $text $dir/chess-2x2.jpg
 convert -size 100x100 pattern:gray50 -scale 800%x1600% -sampling-factor 1x2 \
-    -crop 796x396+0+0 $dir/chess-1x2.jpg
+    -crop 796x396+0+0 $text $dir/chess-1x2.jpg
 convert -size 100x100 pattern:gray50 -scale 1600%x800% -sampling-factor 2x1 \
-    -crop 796x396+0+0 $dir/chess-2x1.jpg
+    -crop 796x396+0+0 $text $dir/chess-2x1.jpg
 convert -size 100x100 pattern:gray50 -scale 800% -sampling-factor 1x1 \
-    -crop 796x396+0+0 $dir/chess-1x1.jpg
+    -crop 796x396+0+0 $text $dir/chess-1x1.jpg