Convert Photoshop PSD to ICO

The Photoshop Document (PSD) is the proprietary file format of Adobe Photoshop, capable of storing an image with support for all available imaging options including layers, adjustment layers, layer masks, alpha channels, paths, and vector text. It utilizes Run-Length Encoding (RLE) for compression and allows for a maximum file size of 2 GB and dimensions up to 30,000 pixels. The format maintains the editing history and non-destructive elements of a project, unlike flattened raster formats. The internal structure is divided into five parts: File Header, Color Mode Data, Image Resources, Layer and Mask Information, and Image Data.

Adobe Photoshop is the primary software for full PSD support. However, several other programs offer varying degrees of compatibility. GIMP (GNU Image Manipulation Program) and Paint.NET (with a plugin) can open PSD files but may not render complex layer styles or adjustment layers correctly. CorelDRAW and Affinity Photo also provide robust support. For simple viewing without editing, standard image viewers like XnView or IrfanView can often display the flattened composite preview embedded within the file.

The ICO format is an image container specifically designed for Microsoft Windows to store icons for executable files, folders, and applications. Introduced with Windows 1.0, it can encapsulate multiple raster images of varying dimensions and color depths (specifically BMP or PNG frames) within a single file to support dynamic scaling across different display resolutions. The structure comprises an ICONDIR header referencing one or more ICONDIRENTRY directory entries, allowing the operating system to select the appropriate 16x16, 32x32, or 48x48 pixel resource based on the current UI scaling settings.

ICO files are natively supported by the Microsoft Windows operating system, which automatically renders them in the File Explorer and taskbar. On macOS, Apple Preview handles the format natively. For editing or detailed inspection of the contained bitmap layers, raster graphics editors such as GIMP, Adobe Photoshop (via plugin), or Paint.NET are required. Web browsers also natively render ICO files when they are designated as favicons.