Treasure hunt for edges - imagemagick

Question

I want to make a children's treasure hunt where the next location is given by a picture e.g.
To make a more suitable printable picture, I can use -canny like this:
convert hut.jpg -canny 0x1+10%+30% -negate hutCanny.jpg
To make it more interesting, I was thinking that I want to make two images -one with horizontal lines and one with vertical lines:
convert hut.jpg -colorspace gray -morphology Convolve Sobel -negate hutH.jpg
convert hut.jpg -colorspace gray -morphology Convolve Sobel:90 -negate hutV.jpg
I would like the location to be only guessable when both picture are found and can be combined using a light source. The problem is that Sobel not only detects vertical lines but also angled lines. As can be seen, the location is far too easy to recognise with just one picture. I have been trying with different kernels and trying to erode the pictures. -nothing woks.
How do I make two images that by themselves are not 'guessable' but can be combined to one. e.g. by making one image with only near horizontal lines and an other with only near vertical lines?

Answer 1

You could do something like the following in ImageMagick. Make a random mask and apply it to the image. Then invert the mask and do the same. The two images, when added together, will make the input.
Input:
convert \( hut.png -write mpr:img +delete \) \
\( mpr:img +noise random -channel g -separate +channel -blur 0x5 -threshold 50% +write mpr:mask +delete \) \
\( mpr:img mpr:mask -compose multiply -composite +write hut_out1.png \) \
\( mpr:img \( mpr:mask -negate \) -compose multiply -composite +write hut_out2.png \) \
null:
Output 1:
Output 2:
ADDITION
If it has to be grayscale, then you can do the above and make each output gray.
convert \( hut.png -write mpr:img +delete \) \
\( mpr:img +noise random -channel g -separate +channel -blur 0x5 -threshold 50% +write mpr:mask +delete \) \
\( mpr:img mpr:mask -compose multiply -composite -colorspace gray +write hut_out1.png \) \
\( mpr:img \( mpr:mask -negate \) -compose multiply -composite -colorspace gray +write hut_out2.png \) \
null:
Output 1:
Output 2:
Now add them together to reconstitute:
convert hut_out1.png hut_out2.png -evaluate-sequence add hut_out12.png