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jaewonjoo / webp

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Illegible text in ksnapshot webp image #252

Closed GoogleCodeExporter closed 8 years ago

GoogleCodeExporter commented 8 years ago 
What steps will reproduce the problem?
1. Take a screenshot of text with ksnapshot in Fedora Linux
2. Select Save as
3. Select webp as the image type

What is the expected output? legible text

What do you see instead? illegible text

What version of the product are you using? KSnapshot 0.8.2

On what operating system? Fedora 19

Please provide any additional information below.

I attached the same snapshot using .png, .jpeg, and .webp formats for examples.

Original issue reported on code.google.com by smcon...@gmail.com on 28 Jun 2015 at 8:05

Attachments:

GoogleCodeExporter commented 8 years ago 
When I take the PNG screenshot and convert it to WebP (using cwebp with default 
quality = 75), the text is clearly legible. See the attachment.

This makes me wonder what WebP quality ksnapshot may be using. I recommend 
filing a bug against ksnapshot: 
https://bugs.kde.org/enter_bug.cgi?format=guided&product=ksnapshot

Original comment by urv...@google.com on 29 Jun 2015 at 5:50

Attachments:

GoogleCodeExporter commented 8 years ago 
Thanks. Per your suggestion, I reported it here:

https://bugs.kde.org/show_bug.cgi?id=349730

Original comment by smcon...@gmail.com on 29 Jun 2015 at 8:36

GoogleCodeExporter commented 8 years ago 
Marking this as invalid as the issue seems to be on ksnapshot side. Feel free 
to reopen later if needed.

Original comment by urv...@google.com on 29 Jun 2015 at 8:49

GoogleCodeExporter commented 8 years ago 
Note that the original Text\ Sample.webp has a quantization step of 127 (see 
src/dec/quant.c:67).
Which means it has probably been encoded at the minimal quality setting -q 0. 
Something is strange here.

Note also that using *lossless* encoding would yield even better results for 
text.
Attached, is a Text\ Sample\ lossless.webp lossless file of 19kB, almost half 
the size of
the original PNG.

ksnapshot should investigate the quality setting, but also maybe: try both 
lossless and lossy encoding, and pick on the smaller sized output.

Original comment by pascal.m...@gmail.com on 29 Jun 2015 at 10:07

Attachments:

GoogleCodeExporter commented 8 years ago 
Unlike the attached .png and .jpeg images, I'm curious why the attached .webp 
image above doesn't provide a thumbnail and isn't viewable from this page, but 
must be downloaded to be viewed.

Original comment by smcon...@gmail.com on 29 Jun 2015 at 10:17

GoogleCodeExporter commented 8 years ago 
code.google.com server would need some extra code to handle .webp thumbnails 
properly at serve time.

Unfortunately, it's being deprecated and this extra work won't happen.
This bug tracker will be migrated to developers.google.com with the rest of 
WebP.

Original comment by pascal.m...@gmail.com on 29 Jun 2015 at 10:30

GoogleCodeExporter commented 8 years ago 
Didn't this version of ksnapshot have issues with images with alpha as well 
[1]? The webp output looks to be suffering from this. Encoding the png with -q 
0 on the command line looks bad, but is still mostly legible.

[1] https://bugs.kde.org/show_bug.cgi?id=346123

Original comment by jz...@google.com on 29 Jun 2015 at 11:20