Re: Transparency in images

Hi Lora,

If you intend to use the alpha channel PNG, you may need to think about how it will look for "Nigth Mode" when testing in the reading system. On the attached page, the Readium logo is alpha channel PNG. This appears to be when the PNG document is selected in "Nigth Mode".

Best regards

N. Erhan Uzumcu
Art Director and EPUB Designer
TEYTAG Founder
(Turkish Electronic Publishing Design and Research Group - Istanbul, Turkey)
https://independent.academia.edu/NErhanÜzümc��
http://dbookmarksblog.blogspot.com.tr
http://teytagblog.blogspot.com.tr
@ePub3Lib #teytag
W3C EPUB Community Group Member




> On May 10, 2019, at 5:48 PM, Lora Friedenthal <lora@scribd.com> wrote:
> 
> Naomi,
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> It didn't occur to me that alpha channel and transparent were different. Transparent GIF looks like it doesn't use alpha channel, so I'll try again with that. Thanks!
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> Lora Friedenthal
> Pronoun(s): She/Her/Hers
> Content Operations Specialist at Scribd
>  <http://www.facebook.com/scribd>  <http://www.linkedin.com/company-beta/129665/>  <http://twitter.com/scribd>
> 
> On Fri, May 10, 2019 at 10:05 AM Kennedy, Naomi E <nkennedy@penguinrandomhouse.com <mailto:nkennedy@penguinrandomhouse.com>> wrote:
> Hey Lora,
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> 
> From a spec perspective, transparency may be supported. The EPUB spec directly references the full PNG spec, and the PNG spec says that transparency may be ignored (it’s considered ancillary information <https://www.w3.org/TR/PNG/#11Ancillary-chunks>). I’m not sure about the gif spec but I would assume it has similar wording (it’s a much older spec and not written in a way I can understand).
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> On a more practical note: We have found that the way we create transparency is supported by most of the big US retailers, but not all (specifically the big one that doesn’t support epub doesn’t support transparency). If by “transparency layer” you are referring to an “alpha channel”, we didn’t test that since none of our tools create alpha channels. That could be the reason for the discrepancy between our testing and yours.
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> Hope that helps,
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> Naomi
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> From: Lora Friedenthal <lora@scribd.com <mailto:lora@scribd.com>>
> Date: Thursday, May 9, 2019 at 7:05 PM
> To: "public-epub3@w3.org <mailto:public-epub3@w3.org>" <public-epub3@w3.org <mailto:public-epub3@w3.org>>
> Subject: Transparency in images
> Resent-From: <public-epub3@w3.org <mailto:public-epub3@w3.org>>
> Resent-Date: Thursday, May 9, 2019 at 6:59 PM
> 
>  
> 
> Hello. Can someone tell me whether transparency layers in PNG and GIF are supported in EPUB3? I assume since every viewer shows a white box around images it must not be, but I also can't find anywhere in the spec that says it shouldn't work. I'm trying to determine if we just have to live with ornaments in the text being in white boxes when users change the background color of the reader. 
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> Lora Friedenthal
> Pronoun(s): She/Her/Hers
> Content Operations Specialist at Scribd
> 
>  <http://www.facebook.com/scribd>  
>  <http://www.linkedin.com/company-beta/129665/>  
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