ImageMagick: Cylinder keeping original on background

Question

I'm trying to make a cylinder wrap via ImageMagick. It's working fine on creating the cylinder, but it's keeping the original image on back.

magick \
-verbose \
\( \
      -size 2585x1181 \
      xc:blue \
      \( \
         ./images/test.png \
         -geometry +820+0 \
      \) \
      -composite \
      -geometry 730x390 \
      -roll -230+0 \
      -crop 270x408+0+0 \
      +append \
\) \
-gravity south -background Transparent -splice 0x40 \
\( +clone -sparse-color barycentric '0,0 black 273,0 white' \) \
\( -clone 1 -function arcsin 0.5 \) \
\( -clone 1 -level 0%,100% \
            -function polynomial -4,4,0 -gamma 2 \
            +level 50%,0%  \) \
-delete 1 \
-virtual-pixel Transparent \
-define compose:args=0x40 \
-compose Displace \
-composite \
./output/out.png

Thoughts?

Thanks

Answer 1

The issue is that in Imagemagick 7, whether a bug or a design feature, the distortion needs to be composed as one image with the X and Y distortions in the first two channels rather than as separate images.

In Imagemagick 6, this works

convert \
-verbose \
\( \
      -size 2585x1181 \
      xc:blue \
      \( \
         test.png \
         -geometry +820+0 \
      \) \
      -composite \
      -resize 730x390 \
      -roll -230+0 \
      -crop 270x408+0+0 +repage \
\) \
-gravity south -background none -splice 0x40 \
\( -clone 0 -set colorspace Gray -alpha off -sparse-color barycentric '0,0 black 270,0 white' \) \
\( -clone 1 -function arcsin 0.5 \) \
\( -clone 1 \
            -function polynomial -4,4,0 -gamma 2 \
            +level 50%,0% \) \
-delete 1 \
-background none -virtual-pixel none \
-define compose:args=20x40 \
-compose Displace \
-composite \
test_out1.png

But in Imagemagick 7, you have to do

magick \
\( \
      -size 2585x1181 \
      xc:blue \
      \( \
         test.png \
         -geometry +820+0 \
      \) \
      -composite \
      -geometry 730x390 \
      -roll -230+0 \
      -crop 270x408+0+0 \
\) \
-gravity south -background Transparent -splice 0x40 \
\( +clone \
   -set colorspace Gray \
   -alpha off \
   -sparse-color barycentric '0,0 black 273,0 white' \
  \( -clone 0 -function arcsin 0.5 \) \
  \( -clone 0 \
     -function polynomial -4,4,0 -gamma 2 \
     +level 50%,0%  \) \
  \( +clone \) \
  -delete 0 \
  -combine \
  -alpha off \
\) \
-virtual-pixel Transparent \
-define compose:args=20x40 \
-compose Displace \
-composite \
+channel \
test_out3.png