[CREATE] CREATE Digest, Vol 164, Issue 4

[Johann ELSASS]

Hello Paul,

I would favor backward compatibility. In this case, it would be better to keep the layer stack structure as it is and provide a PNG in all cases. New features would be either attributes, nodes inside existing nodes, or other XML files within the archive.

To Alex: For the same reason, I am not in favor either of changing the format of the images to EXR. Though as I side note, we can specify not to compress PNG files within the archive, as PNG is already somewhat ZIP compressed. That can improve speed a bit.

Regarding layer effects, it is more of a theoretical discussion, because it is unlikely that various programs have the same effects. A generalized function will probably not cover all cases. Nevertheless SVG has the ability to generate effects (for example blur), so in theory why not use them.

In my application (LazPaint), for now, I generate layers with effects (shadow, stroke) and add them above or beneath as raster. Information on how I generated them is stored in a "registry": for each layer, a dictionary of values. In the OpenRaster file only the raster result is saved and not this meta-information.

Regarding vectors, maybe the simplest for readers is to have an SVG file, as well as a PNG file, within the archive. This allows as well anyone to view the content just by unpacking the archive. One thing to consider is that the SVG format has a DPI by default, its size is not specified in pixels, so either we use this default value, or we set it explicitely when using an SVG file. Otherwise, we could of course include the SVG tag inside the layer tag, to indicate: hey this is the vector content.

I am not sure what you mean by affine transformations as masks. Though regarding masks, I think it would be handy to add a blend operation that corresponds to applying an alpha mask. This way, one could have a layer with a mask by adding a layer group with the image and with the mask on top of that using the mask blend op.

Regards,

-- 
  Johann ELSASS
  circular at operamail.com