fix: use width to calculate rowstride

[spazziale]

No description provided.

[rubdos]

Can we throw in some test to catch the previous faulty behaviour, also for image?

[codecov]

Codecov Report

Merging #11 (b1fc8d6) into main (9ed0f0f) will increase coverage by 1.37%.
Report is 2 commits behind head on main.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #11      +/-   ##
==========================================
+ Coverage   88.11%   89.49%   +1.37%     
==========================================
  Files           6        6              
  Lines         244      276      +32     
==========================================
+ Hits          215      247      +32     
  Misses         29       29              

Files Changed	Coverage Δ
src/lib.rs	96.59% <100.00%> (+0.75%)	⬆️

[spazziale]

Can we throw in some test to catch the previous faulty behaviour, also for image?

I don't think that is needed/possible to do with image