Re: Digest for webp-discuss@webmproject.org - 4 updates in 1 topic

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Dustin Albert

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Jul 16, 2021, 2:27:01 AMJul 16
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On Fri, Jul 16, 2021, 1:07 AM <webp-d...@webmproject.org> wrote:
"ygu… via monorail" <monorail+norep...@chromium.org>: Jul 15 02:55AM -0700

Comment #2 on issue 533 by ygu...@google.com: cwebp doesn't support alpha - from command line
https://bugs.chromium.org/p/webp/issues/detail?id=533#c2
 
I tried the following on Windows:
libwebp-1.2.0-windows-x64\bin\cwebp.exe -q 70 "3 hits.webp" -o "newImage.webp"
and the equivalent on Linux, they both produce the attached image, which has alpha as expected.
Could you check that the command line you gave was the one you used, and also the input/output images?
Did you build or download the binaries?
 
Attachments:
newImage.webp 11.6 KB
 
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"kiloo… via monorail" <monorail+norep...@chromium.org>: Jul 15 08:48AM -0700

Comment #3 on issue 533 by kiloo...@gmail.com: cwebp doesn't support alpha - from command line
https://bugs.chromium.org/p/webp/issues/detail?id=533#c3
 
That is very weird, I downloaded the binaries.
 
Attached below a short clip of the process, hope this helps figure out whats going on.
 
Attachments:
2021-07-15 16-46-03.mkv 3.0 MB
 
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"ygu… via monorail" <monorail+norep...@chromium.org>: Jul 15 09:23AM -0700

Comment #4 on issue 533 by ygu...@google.com: cwebp doesn't support alpha - from command line
https://bugs.chromium.org/p/webp/issues/detail?id=533#c4
 
Thank you for the video. This is strange indeed.
 
For comparison this is the beginning of the output of my ./cwebp -q 70 "3 hits.webp" -o "newImage.webp":
Saving file 'newImage.webp'
File: 3 hits.webp
Dimension: 1920 x 1080 (with alpha)
...
 
We can see that "with alpha" is missing in the log of your video. It seems the decoding is erroneous here, rather than the encoding.
 
For reference:
./webpinfo "3 hits.webp"
File: 3 hits.webp
RIFF HEADER:
File size: 36810
Chunk VP8X at offset 12, length 18
ICCP: 0
Alpha: 1
...
md5sum "3 hits.webp"
57363e25d6896442ab03b4f085367afb 3 hits.webp
 
Could you run webpinfo and md5 too, to compare the results?
Could you also try opening your source image with other tools, such as GIMP, Photoshop+WebPShop, and/or ImageMagick?
 
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"kiloo… via monorail" <monorail+norep...@chromium.org>: Jul 15 02:20PM -0700

Comment #5 on issue 533 by kiloo...@gmail.com: cwebp doesn't support alpha - from command line
https://bugs.chromium.org/p/webp/issues/detail?id=533#c5
 
Could you run webpinfo and md5 too, to compare the results?
D:\Oscar Six\Desktop>libwebp-1.2.0-windows-x64\bin\webpinfo.exe "3 hits.webp"
File: 3 hits.webp
RIFF HEADER:
File size: 36810
Chunk VP8X at offset 12, length 18
ICCP: 0
Alpha: 1
EXIF: 0
XMP: 0
Animation: 0
Canvas size 1920 x 1080
Chunk ALPH at offset 30, length 13908
Chunk VP8 at offset 13938, length 22872
Width: 1920
Height: 1080
Alpha: 0
Animation: 0
Format: Lossy (1)
No error detected.
 
MD5: 57363e25d6896442ab03b4f085367afb
 
 
D:\Oscar Six\Desktop>libwebp-1.2.0-windows-x64\bin\webpinfo.exe "newImage.webp"
File: newImage.webp
RIFF HEADER:
File size: 3800
Chunk VP8 at offset 12, length 3788
Width: 1920
Height: 1080
Alpha: 0
Animation: 0
Format: Lossy (1)
No error detected.
 
MD5: 1212d3dadc30af7d4461416ee11a6401
 
Openning the "3 hits.webp" file in GIMP gives the following result (see attached image)
 
Attachments:
Screenshot 2021-07-15 222016.png 165 KB
 
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