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Subject: Color and tone adjustments specifications need improvement

Hi all,

This is about problems I see in the specification of draw:blue, draw:red, draw:gree, draw:luminance, draw:contrast, and draw:gamma. I have not written a JIRA issue yet, because I do not know, how cases with multiple, connected problems are handled.

The ODF specification does not provide any information how the draw:gamma value has to be used when rendering an image. The .png format has a chunk gAMA, which holds a gamma value. http://www.w3.org/TR/PNG/#3gamma. And in that specification you get a detailed description, how this value is to be used for displaying a .png picture. http://www.w3.org/TR/PNG/#13Decoder-gamma-handling. I think the ODF specification needs such kind of description too.

The attribute draw:blue has already a description (and thereby draw:green and draw:red).Such description is missing for draw:contrast and draw:luminance.

In the specification of draw:blue the output value is restricted to the interval given by the color depth. But in AOO this restriction is done only after draw:luminance, draw:contrast, and draw:gamma are applied too. ODF 1.2 specification does not consider the other filters at all.

The gamma-filter is non-linear. When combining it with another filter, the result depends on the order in which the filters are applied. ODF 1.2 specification does not contain an information about the order. The schema has <interleave> for the elements of "style-graphic-properties-attlist".

The data type of draw:gamma is "percent". That would include non-positive values too. But in all cases I have found, it is a positive value. In fact applications often restrict the values in the UI, e.g. PaintShopPro 0.2 to 5.0, IrfanView 0.01 to 6.99, AOO 0.1 to 10.0.

It is possible to set a background to an image using draw:fill. ODF1.2 specification does not state, whether the filters are applied to the background too. In AOO the background is not affected.

ODF 1.2 specification uses "pixel image" and "bitmap or raster graphic". It is not clear to me, whether that is the same. If yes, the same wording should be used in all places.

In AOO the color and tonal adjustments work on metafiles and .svg graphics too, for example characters in metafiles or gradients in .svg graphics are affected by the color filters. Therefore "pixel" or "raster" might not be correct at all.

I have written a description based on the way AOO does it. Because plain text is not so good for formulas, I have attached the description as .odt document. The document is not meant as ready proposal, but to illustrate, what I'm missing.

Kind regards

Attachment: OASIS.odt
Description: application/vnd.oasis.opendocument.text

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