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Fix: add alpha premultiplication steps before and after resize #302

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merged 3 commits into from
Feb 19, 2024
Merged

Fix: add alpha premultiplication steps before and after resize #302

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a35e5a4
Add alpha premultiplication steps before and after resize
KaarlisCaune Jan 30, 2024
3a9bc30
Only premultiply if image has alpha
KaarlisCaune Feb 6, 2024
ef544cd
Fix transparent images not being resized, add test
KaarlisCaune Feb 18, 2024
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8 changes: 7 additions & 1 deletion lib/jekyll_picture_tag/images/image_file.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,13 @@ def notify
end

def resize(image)
image.resize(scale_value)
if image.has_alpha?
image = image.premultiply
image = image.resize(scale_value)
image.unpremultiply
else
image.resize(scale_value)
end
end

def crop(image)
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Binary file added test/image_files/pestka_transparent.png
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9 changes: 9 additions & 0 deletions test/unit/images/test_image_file.rb
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Expand Up @@ -129,6 +129,15 @@ def test_resize
assert_equal(10, width)
end

def test_resize_with_alpha
restub_source('pestka_transparent', 'png')
tested

width = Vips::Image.new_from_file(filename).width

assert_equal(10, width)
end

def test_quality
# We have to use slightly larger images for the quality to make a difference
# in file size.
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