The OpenRaster spec currently states (working from memory here) that ORA files may use uses the SVG compositing ops[1]. These do not provide colorize layer modes, nor modes for luminosity-setting, hue-setting or saturation-setting. I'd quite like to implement these but because it would require a change to the OpenRaster specification, I haven't yet. Users are clamouring for it however, and I think MyPaint should implement colourize at least (not to mention I have some sample code kicking around locally).
Currently layers with compositing modes other than "svg:src-over" are written to layers.xml with a suitable "composite-op" attribute: <layer composite-op="svg:src-over" opacity="1.0" src="data/layer001.png" visibility="visible" x="0" y="0" /> What I suggest doing is extending the current definition with the following modes: * SOMEPREFIXhue - src hue, and luminance and saturation of the dst * SOMEPREFIXsaturation - saturation of the src layer, with the hue and luminance of the dst * SOMEPREFIXcolor - hue and saturation of the src, with the luminance of the dst * SOMEPREFIXluminosity - luminance of the src, over the hue and saturation of the dst Definitions of these blending modes can be found in various PDF specifications[2], and work well up until one has to composite with an opacity setting using scaled ints. Which is a whole new kind of fun. What should we use for SOMEPREFIX? "pdf:blend-" is one possibility if we want to slavishly adopt that... but I'd rather refer to a more open specification if I can (not to mention that I want to use the Rec. 709 primaries[3] for the perceptual-ish bit). Current SVG specification (1.1) is indeed luminosity/luma aware for feColorMatrix, but does not define these blend modes, sadly. MyPaint could of course just do its own thing here, or copy Krita. I've had a quick poke around the Krita and GIMP implementations of these layer modes, but they seem to use HSV only, which seems limiting. Is there any particular reason for this? [1] http://www.w3.org/TR/SVGCompositing/ [2] The shortest and most relevant one is probably the "PDF Blend Modes: Addendum" for the PDF Reference, fifth edition, version 1.6, dated Jan 23 2006 - available from Adobe via your search engine of choice. [3] https://en.wikipedia.org/wiki/Rec._709 -- Andrew Chadwick _______________________________________________ CREATE mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/create
