Vips::Image.thumbnail and Vips::Image.thumbnail_image resize to height instead of width when no hash options are present

[i-h8-github]

Bug report

Describe the bug
Vips::Image.thumbnail and Vips::Image.thumbnail_image resize to height instead of width when no hash options are present. If a :height is also supplied, they will resize to the expected width

To Reproduce

img = Vips::Image.new_from_file "file.pdf"
puts "#{img.width}, #{img.height}" # 612, 859
thumb = img.thumbnail_image 200
puts "#{thumb.width}, #{thumb.height}" # 142, 200
thumb = img.thumbnail_image 200, :height => 1000
puts "#{thumb.width}, #{thumb.height}" # 200, 281

thumb = Vips::Image.thumbnail "file.pdf", 200
puts "#{thumb.width}, #{thumb.height}" # 143, 200 — Different height from above for some reason
thumb = Vips::Image.thumbnail "file.pdf", 200, :height => 1000
puts "#{thumb.width}, #{thumb.height}" # 200, 281

Expected behavior
Should resize to specified width as described

Actual behavior
Resizes to a height of the specified width

Environment

• OS: Ubuntu 24.04
• Vips: 8.16.0

[jcupitt]

Please don't cross-post, it creates unnecessary extra work for volunteer maintainers.

See libvips/libvips#4312

[i-h8-github]

Please don't cross-post, it creates unnecessary extra work for volunteer maintainers.

See libvips/libvips#4312

Sorry, I wasn't sure where this belonged.

I don't understand why this is closed, though. Even if it is intended behavior, it is a bug in the behavior of ruby-vips as documented.

[jcupitt]

The ruby-vips docs are generated automatically and aren't definitive. The C docs are the real ones.

We ought to improve the ruby-vips docs. We have the main docs as marked up XML, we really ought to make something to merge them into the ruby docs. I think no one's founds the time yet.