A PSD file is an image file created by Adobe Photoshop, a professional image-editing program often used to enhance digital photos and create web graphics. It is the native format used to save files in Photoshop. PSD files may include image layers, adjustment layers, layer masks, annotations, file information, keywords, and other Photoshop-specific elements. They are commonly created and shared among graphics professionals.
You can modify PSD layers and other elements such as images, shapes, text, and effects. The PSD format supports RGB, CMYK, grayscale, monochrome, duotone, indexed color, Lab color, and multichannel color modes. The color mode can be changed within the submenu. When you are ready to publish the image, you can export it to standard image formats such as .JPEG, .GIF, and .PNG.
While PSD files are saved in a proprietary format, they can be opened directly with Apple Preview, which is included with OS X. They can also be opened by media programs included with Windows if the correct codec, such as the Ardfry PSD codec, is installed. Examples include Windows Explorer, Windows Photo Viewer, and Windows Media Center.
What is the data structure of a PSD file?
The Photoshop file format is separated into five major parts:
- File Header - contains the basic properties of the image such as the version, number of channels in the image, number of bits per channel, pixel height and width of the image, and the color mode of the file (bitmap, grayscale, RGB, CMYK, Multichannel, indexed, duotone, and lab).
- Color Mode Data - specifies the length of the color data, which is set to 0 unless the color mode is indexed or duotone as specified in the file header. If this is the case, the color data for indexed color and duotone images is also stored in this section.
- Image Resources - specifies the length of the image resource section and the image resources, which is a series of blocks each with a resource ID that indicates the type of data stored in the block. These blocks are used to store non-pixel data associated with the image, such as pen or pencil tool paths.
- Layer and Mask Information - contains information about layers and masks, which includes the number of layers, channels in the layers, blending ranges, adjustment layer keys, effects layers, and mask parameters.
- Image Data - contains the actual image data and the data compression method and the image pixel data. Different compression methods may be raw image data, RLE compression, Zip without prediction, or Zip with prediction.