Issue 487 in webp: Gif to webp, quality set to 40, webp's size is bigger than gif

[oishi… via monorail]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 487 by oishi...@gmail.com: Gif to webp, quality set to 40, webp's size is bigger than gif
https://bugs.chromium.org/p/webp/issues/detail?id=487

What steps will reproduce the problem?
1.download libwebp-0.4.1-windows-x64 file.
2.use command convert gif to webp: gif2webp.exe -m 4 -q 40 fail.gif -lossy -o gif-quality-40.webp
3.output gif-quality-40.webp

What is the expected output? What do you see instead?

EA: most of gif file convert to webp quality 40 file, file size decrease too much, but his file size increase

What version of the product are you using? On what operating system?
libwebp-0.4.1-windows-x64

Please provide any additional information below.

Attachments:
fail.gif 535 KB
gif-quality-40.webp 620 KB

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[pasca… via monorail]

Updates:
Status: Done

Comment #1 on issue 487 by pasca...@gmail.com: Gif to webp, quality set to 40, webp's size is bigger than gif
https://bugs.chromium.org/p/webp/issues/detail?id=487#c1

Using lossy compression when the input is a gif (that is: ~256 colors) usually results in larger files. This is due to the color-space used by lossy compression. You would have a similar problem when trying to recompress a PNG file to JPEG, for instance.

But if you use *lossless* compression (the default) and try to minimize the output size, you'll get a 500kb file.

gif2webp fail.webp -min_size -o fail.webp

Note that the input GIF has a dithering pattern which is often hard to compress. This could explain why the size reduction is not larger.

Additionally, you should use a more recent version of libwebp, 0.4.1 being quite old.
The latest one (1.1.0) is available here: https://developers.google.com/speed/webp/docs/precompiled

Attachments:
fail.webp 492 KB

[oishi… via monorail]

Comment #2 on issue 487 by oishi...@gmail.com: Gif to webp, quality set to 40, webp's size is bigger than gif
https://bugs.chromium.org/p/webp/issues/detail?id=487#c2

i download libwebp-1.1.0-windows-x64
size is bigger than libwbep-0.4.1

F:\libwebp-1.1.0-windows-x64\bin>gif2webp.exe -q 40 -lossy fail.gif -o fail.webp
Saved output file (640616 bytes): fail.webp

[oishi… via monorail]

Comment #3 on issue 487 by oishi...@gmail.com: Gif to webp, quality set to 40, webp's size is bigger than gif
https://bugs.chromium.org/p/webp/issues/detail?id=487#c3

get it, thank you