.ORA

Introduction

OpenRaster is an open format for layered images, made so that painting and image editing programs can pass layered work between them. It is deliberately simple: each layer is an ordinary PNG, and one XML file says how they stack.

It is the native format of MyPaint, and Krita, GIMP and Pinta can open and save it. Layer effects and settings that only one program understands are lost on the way.

Structure

An ORA file is a zip archive. Its first entry is an uncompressed file named mimetype holding image/openraster. Next comes stack.xml, which lists the layers and groups from top to bottom with their position, opacity, visibility and blend mode, and points to each layer’s image. The layer images sit in a data/ folder, usually as PNG files. A thumbnail is stored at Thumbnails/thumbnail.png, and newer files also hold the flattened picture as mergedimage.png.

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