Merge branch 'aspect-resize-improvements'

Fixes #10.

* aspect-resize-improvements:
  tests/gen-tests-mk: avoid bias in randomized aspect ratio distribution
  tests/Makefile: use wmtool.py for j90randomsizej80 attack
	See #10.
  tests/gen-tests-mk: use new wmtool.py compatible format for randomsize.inc
	See #10.
  tests/wmtool.py: implement "aspect-resize:<width>:<height>" attack
	Add new wmtool.py attack as suggested in #10 to avoid extreme aspect
	ratio changes.

Signed-off-by: Stefan Westerfeld <stefan@space.twc.de>

Author: swesterfeld

tests/Makefile

@@ -91,7 +91,7 @@ j90scaleto512j70	= $(SRCDIR)/tests/wmtool.py --seed $1 --attack "jpeg:90|scaleto
 j90scaleto768j90	= $(SRCDIR)/tests/wmtool.py --seed $1 --attack "jpeg:90|scaleto:768|jpeg:90" $< $@.png && mv $@.png $@
 j90scaleto768j70	= $(SRCDIR)/tests/wmtool.py --seed $1 --attack "jpeg:90|scaleto:768|jpeg:70" $< $@.png && mv $@.png $@
 j90scaleto768j50	= $(SRCDIR)/tests/wmtool.py --seed $1 --attack "jpeg:90|scaleto:768|jpeg:50" $< $@.png && mv $@.png $@
-j90randomsizej80	= convert $< -quality 90 $@.1.jpg && convert $@.1.jpg -resize $(RANDOMSIZE)! -quality 80 $@.2.jpg && rm $@.1.jpg && mv $@.2.jpg $@
+j90randomsizej80	= $(SRCDIR)/tests/wmtool.py --seed $1 --attack "jpeg:90|aspect-resize:$(RANDOMSIZE)|jpeg:80" $< $@.png && mv $@.png $@
 # centered cropping (detectable by corner sync)
 crop75j90		= convert $< -gravity Center -crop 75x75%+0+0 -quality 90	$@.jpg && mv $@.jpg $@
 crop50scale200j90	= convert $< -gravity Center -crop 50x50%+0+0 -resize 200% -quality 90	$@.jpg && mv $@.jpg $@

tests/gen-tests-mk

@@ -102,7 +102,8 @@ def generate_resolutions (resolution_icdf, resolution_min, resolution_max, num_s
   resolutions2d = []
   for reso in generated_resolutions:
     total_pixels = reso * reso
-    ratio = random.uniform (min_ratio, max_ratio)
+    log_ratio = random.uniform (np.log (min_ratio), np.log (max_ratio))
+    ratio = np.exp (log_ratio)
     width  = round (np.sqrt (total_pixels * ratio))
     height = round (np.sqrt (total_pixels / ratio))
     resolutions2d.append ((width, height))
@@ -181,7 +182,7 @@ def main():
     imgname = 'img%05u' % imgcounter
     dstname = os.path.join (inputsdir, imgname)
     rw, rh = resolutions2d[imgidx]
-    target_sizes.append ((imgname, f"{rw}x{rh}"))
+    target_sizes.append ((imgname, f"{rw}:{rh}"))
     if symlink (src_image_path, dstname):
       eprint ("  SYMLINK", dstname, "->", src_image_path, f"(target size: {rw}x{rh})")
     else:

tests/wmtool.py

@@ -135,6 +135,34 @@ def attack_aspect (img, amin, amax):
 
   return cv2.resize (img, (width, height))
 
+epilog += """
+* aspect-resize:<width>:<height>
+
+  change aspect ratio of the image, avoiding extreme aspect ratio changes
+  if aspect ratio change is in 9:16..16:9
+    - rescale to <width> x <height> pixels
+  if aspect ratio change is extreme (outside 9:16..16:9)
+    - rescale to <height> x <width> pixels unless this is even more extreme
+
+  this is mainly a helper for the j90randomsizej80 attack of gen-tests-mk
+"""
+def attack_aspect_resize (img, width, height):
+  def aspect_delta (old_size, new_size):
+    delta = (old_size[0] / old_size[1]) / (new_size[0] / new_size[1])
+    if (delta < 1):
+      delta = 1 / delta
+    return delta
+  old_height, old_width = img.shape[0], img.shape[1]
+  delta = aspect_delta ((old_width, old_height), (width, height))
+  delta_swap = aspect_delta ((old_width, old_height), (height, width))
+  if delta > 16/9 and delta_swap < delta:
+    width, height = height, width
+    swap = " (swap)"
+  else:
+    swap = ""
+  print_attack ("ATTACK aspect-resize %dx%d to %dx%d%s" % (old_width, old_height, width, height, swap))
+  return cv2.resize (img, (width, height))
+
 epilog += """
 ------------------------------------------------------------------------------
 Example:
@@ -228,6 +256,8 @@ def load_bgr_image (filename):
       face = attack_rotate (face, int (aargs[1]), int (aargs[2]))
     elif aargs[0] == "aspect" and len (aargs) == 3:
       face = attack_aspect (face, int (aargs[1]), int (aargs[2]))
+    elif aargs[0] == "aspect-resize" and len (aargs) == 3:
+      face = attack_aspect_resize (face, int (aargs[1]), int (aargs[2]))
     elif aargs[0] == "none" and len (aargs) == 1:
       pass
     else: