Dylan M. Taylor
7d4d2f4648
The format half of PhotoCraft's OpenRaster import and export (crates/io/src/ora.rs at abeb16c96): the archive and its mimetype, stack.xml as a tree of layers and stacks with the attributes the file has, the 0.0.6 group isolation rule, and a writer. PNG coding, blend-mode mapping, rendering and warnings stay in the app. stack.xml is read with craft-xml and the archive with the zip crate.
1.9 KiB
craft-ora
OpenRaster documents (.ora), read and written. Written from the public specification
(https://www.openraster.org/, stack.xml 0.0.x).
An OpenRaster document is a ZIP whose first, stored entry is mimetype = image/openraster. It
holds stack.xml (the layer tree), one PNG per layer, mergedimage.png (the whole image) and
Thumbnails/thumbnail.png.
is_ora,zip_mimetype: recognise an archive by its first entry, without unzipping.Archive::open: checks the mimetype and readsstack.xmlinto anImage:Node::Layer,Node::StackandNode::Other, topmost first, with the attributes the file has (name,visibility,opacity,composite-op,edit-locked,alpha-preserve,x,y,src,isolation).Archive::entryreads a layer image or any other entry under a size limit.Image::explicit_group_isolation: whether the file's version (0.0.6 and later) makesisolationexplicit, or leaves pass-through to be inferred as older files do.Image::to_xmlandWriter: writestack.xmland the archive, mimetype first, entries stored.
Layer images are PNG; decoding and encoding them is the caller's, as is what a composite-op
means. SVG_COMPOSITE_OPS lists the names the specification defines.
Limits
| Limit | Value |
|---|---|
| Canvas side | 300,000 px (MAX_SIDE); layer offsets up to four times that |
| Canvas area | 1 GiB at 8 bytes per pixel (MAX_PIXEL_BYTES) |
| Elements under the root stack | 8192 (MAX_NODES) |
stack.xml |
16 MiB, 512 levels of nesting, no document type declaration |
| An entry | the caller's limit; MAX_ENTRY (512 MiB) is the suggested one for a layer image |
ZIP
The archive is read and written with the zip crate directly. zip_mimetype (the leading stored
mimetype entry), the bounded entry read and the mimetype-first writer are the same in every
mimetype-first ZIP format and belong in a shared ZIP crate once there is one.