[OASIS Issue Tracker] Commented: (OFFICE-3841) The color mode "Watermark" makes images pale, not transparent

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    [ http://tools.oasis-open.org/issues/browse/OFFICE-3841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=34991#action_34991 ] 

Camilla Boemann commented on OFFICE-3841:
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Rather than focusing on the difference between our implementations I took a look at what a real life watermark is: http://en.wikipedia.org/wiki/Watermark

It is thus clear that neither Calligra nor OO/LO nor the ODF spec does it correctly. A real life watermark is a grayscale image semi-transparently superimposed on the paper (well on top of a potential background image)

So first make it into grayscale using something like: grayValue = (red * 11 + green * 16 + blue * 5) / 32;

then superimpose by say 25% transparency (possibly better would be some kind of bracketing like LO/AOO does with  luminance currently)

Looking at screenshots of MS Word it seems to be what it does too. However MS Word can take the grayscale and color is. And also the semi-transparency is optional. Neither of those MS Word extra features are true to real life though.

I'm not saying we should adopt something like this, but it offers another perspective.

> The color mode "Watermark" makes images pale, not transparent
> -------------------------------------------------------------
>
>                 Key: OFFICE-3841
>                 URL: http://tools.oasis-open.org/issues/browse/OFFICE-3841
>             Project: OASIS Open Document Format for Office Applications (OpenDocument) TC
>          Issue Type: Bug
>          Components: Graphics
>    Affects Versions: ODF 1.2
>            Reporter: Regina Henschel
>            Priority: Minor
>             Fix For: ODF 1.3
>
>
> In section 20.104 draw:color-mode ODF1.2 specifies "watermark: colors are modified to make the resulting image transparent." That is wrong, the image becomes pale, not transparent.
> The property is only implemented in LibreOffice and ApacheOpenOffice, not in Calligra and not in MS PowerPoint2010. MS PowerPoint2013 has a general error in display of images with assigned filter and can not be taken as reference. The help text in LibreOffice and AOO says, "The graphic object is raised in brightness and reduced in contrast so that it can be used in the background as a watermark."
> For an errata I suggest to exchange "transparent" with "pale".
> We might consider to describe this filter in more detail in ODF1.3.
> update: It turned out, that Calligra has implemented it in its current version to be a kind of transparent. So now we have an interoperability problem: It has been implemented as "pale" (making light) by OpenOffige.org and in sequal by LibreOffice and AOO over 10 years, and another application implemented it as transparent.

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