.PSD

Introduction

PSD is the native file format of Adobe Photoshop. It keeps a whole working document: every layer with its blend mode and opacity, masks, adjustment layers, text, paths, guides and colour profiles, as well as a flattened copy of the finished image.

Adobe publishes a specification of the format. Documents larger than 30,000 pixels on a side or 2 GB in size use the Large Document Format, PSB, which has the same layout with wider length fields. Many other editors read PSD, though each supports a different share of Photoshop’s features.

Structure

A PSD file has five sections in a fixed order, and all numbers are big-endian. The 26-byte header starts with 8BPS and gives the version (1 for PSD, 2 for PSB), the number of channels, the height and width, the bits per channel and the colour mode. Each later section starts with its own length, so a reader can skip what it does not need.

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