Fix one Col-major case. Make 1 bpp images always [0 1]

[joa-quim]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 86.02%. Comparing base (b98c446) to head (8572cce).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/lepto_funs.jl	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1645      +/-   ##
==========================================
+ Coverage   85.99%   86.02%   +0.03%     
==========================================
  Files         151      151              
  Lines       21120    21121       +1     
==========================================
+ Hits        18162    18170       +8     
+ Misses       2958     2951       -7     

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