Fix thumbnail size during scale transition

[kbengs]

When page format is changed the thumbnail will not have the right size
until the thumbnail is re-rendered. This commit changes resample so
that thumbnail is scaled until it is re-rendered.

[codecov-io]

Codecov Report

Merging #446 (6e04713) into main (250cbc5) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #446      +/-   ##
==========================================
+ Coverage   71.96%   71.97%   +0.01%     
==========================================
  Files          10       10              
  Lines        2657     2658       +1     
==========================================
+ Hits         1912     1913       +1     
  Misses        745      745              

Impacted Files	Coverage Δ
pdfarranger/croputils.py	90.16% <100.00%> (+0.04%)	⬆️

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[dreua]

I'm not sure I understand the issue here, can you give me the steps to reproduce? The thumbnails look fine to me after cropping or scaling.

[kbengs]

Yep, the steps are: (in main)

• Open a pdf where it takes several seconds to render all pages
• Change scale factor for last page to 200%
• Notice how the tumbnail looks like while you wait for the thumbnail to be re-rendered (it's too small)

Edit:
I changed to draft because I think it works even better if 1/page.zoom is changed to page.resample. I'll investigate.

[kbengs]

The problem with previous code was that if you change scale factor and while you wait for re-rendering of the thumbnail, you change scale factor again. Then the thumbnail would not have the right size.
But that case is fixed now also.

[dreua]

Alright, I'll try to have another look today!