Shrink ASCII art

Question

The inverse of this question.

Your challenge is to, given a piece of ASCII art generated by the above question and its enlargement factor, shrink it down to its original size.

The enlargement process

Or look at this

ASCII art within a limited character set can be enlarged to a certain (odd) size by replacing certain characters with larger versions of themselves, like so:

-\
 |
_/
, 3 =>

   \
--- \ 
     \
    |
    |
    |
     /
    /
___/

Because each character is enlarged to a 3x3 square.

Only those six characters (\/|-_ ) can be enlarged, and only those will be in your input. For a more detailed explanation, see the linked challenge.

I/O may be as a char matrix, ascii art, list of rows, etc.

Testcases

\
 \
  \
, 3 =>
\


         
---------
         
, 3 =>
---


 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | , 3 =>
|
|
|


 | \       / | 
 |  \     /  | 
 |   \___/   | 
 |           | 
 |           | 
 |           | 
   \       /   
    \     /    
     \___/     
, 3 =>
|\_/|
|   |
 \_/ 


_______________
\             /
 \           / 
  \         /  
  /         \  
 /           \ 
/             \
\             /
 \           / 
  \_________/  , 3 => 
_____
\   /
/   \
\___/               
               

        /\        
       /  \       
      /    \      
     /      \     
    /        \    
   /          \   
  /            \  
 /              \ 
/  ____________  \
       |  |       
       |  |       
       |  |       
       |  |       
       |  |       
       |  |       
     /      \     
    /        \    
___/  ______  \___, 3 => 
  /\  
 /  \ 
/____\
  ||  
  ||  
_/__\_


\        /
 \      / 
  \    /  
   \  /   
    \/    
\        /
 \      / 
  \    /  
   \  /   
    \/    , 5 =>
\/
\/


      /             /
     /             / 
    /             /  
   /   -------   /   
  /             /    
 /             /     
/             /      
\             \      
 \             \     
  \             \    
   \   -------   \   
    \             \  
     \             \ 
      \             \, 7 => 
/-/
\-\

Answer 1

Jelly, 7 bytes

»/⁹ÐƤ⁺€

A monadic Link accepting a list of lines that yields a list of lines.

Try it online!

How?

»/⁹ÐƤ⁺€ - Link: list of lists of characters, Lines; pixel size, N
   ÐƤ   - for non-overlapping infixes
  ⁹     - ...of length: chain's right argument, N
 /      - ...yield: reduce by:
        -             maximum (vectorises)
                      (Note: space is less than any other character used)
      € - for each:
     ⁺  -   repeat the last link - i.e. do Ṁ⁹ÐƤ

Answer 2

JavaScript (ES6), 106 bytes

x=>n=>x.replace(/.+\n.+\n.+/g,y=>[...(z=y.split`
`)[~-n/2]].map((w,i)=>i%3-1?"":w<"!"?z[n-1][i]:w).join``)

Now actually works!

Answer 3

J, 20 bytes

{.@-.&' '@,;.3~2 2&$

Try it online!

With (y x,:h w) u;.3 a we can split a into tiles of size h w while sliding the window by y x. Because we don't want overlapping tiles, we can simply build a 2x2 matrix of the input, e.g. 3 3,:3 3. On these tiles u gets applied, which flattens , the tile into a list, removes any whitespace -.&' ' and then reduces the tile to the first remaining element {..

Answer 4

Charcoal, 25 bytes

ＮθＷＳ⊞υ⭆⪪ιθ⌈κＥ⪪υθ⭆⌈ι⌈Ｅι§νμ

Try it online! Link is to verbose version of code. Takes the enlargement factor followed by a list of newline-terminated strings. Explanation:

Ｎθ

Input the enlargement factor.

ＷＳ⊞υ⭆⪪ιθ⌈κ

Input the strings, but split them into substrings of length equal to the enlargement factor and take the maximum character of each substring.

Ｅ⪪υθ⭆⌈ι⌈Ｅι§νμ

Split the list of strings into sublists of length equal to the enlargement factor, then transpose the sublists and take the maximum character of each, joined back into a string, and print each sublist's string on its own line.

Answer 5

JavaScript, 84 bytes

a=>n=>a.map((r,i)=>r.map((c,j)=>(d=b[i/n|0]||=[])[x=j/n|0]=d[x]?.trim()||c),b=[])&&b

f=
a=>n=>a.map((r,i)=>r.map((c,j)=>(d=b[i/n|0]||=[])[x=j/n|0]=d[x]?.trim()||c),b=[])&&b

str2mat = str => str.split('\n').map(r => [...r]);
mat2str = mat => mat.map(r => r.join('')).join('\n');
test = (s, n) => console.log(mat2str(f(str2mat(s.slice(1, -1)))(n)));

test(String.raw`
\
 \
  \
`, 3);

test(String.raw`
---------
`, 3);

test(String.raw`
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
`, 3);

test(String.raw`
 | \       / | 
 |  \     /  | 
 |   \___/   | 
 |           | 
 |           | 
 |           | 
   \       /   
    \     /    
     \___/     
`, 3);

test(String.raw`
_______________
\             /
 \           / 
  \         /  
  /         \  
 /           \ 
/             \
\             /
 \           / 
  \_________/  
`, 3);

test(String.raw`
        /\        
       /  \       
      /    \      
     /      \     
    /        \    
   /          \   
  /            \  
 /              \ 
/  ____________  \
       |  |       
       |  |       
       |  |       
       |  |       
       |  |       
       |  |       
     /      \     
    /        \    
___/  ______  \___
`, 3);

test(String.raw`
\        /
 \      / 
  \    /  
   \  /   
    \/    
\        /
 \      / 
  \    /  
   \  /   
    \/    
`, 5);

test(String.raw`
      /             /
     /             / 
    /             /  
   /   -------   /   
  /             /    
 /             /     
/             /      
\             \      
 \             \     
  \             \    
   \   -------   \   
    \             \  
     \             \ 
      \             \
`, 7);

Answer 6

Haskell, 56 bytes

f n|let g[]=[];g x=maximum(take n x):g(drop n x)=g.map g

Try it online!