A very interesting feature of the JPEG 2000 format is that it supports using a Region of Interest (ROI) to minimize file size and preserve quality in critical areas of an image. By using an alpha channel, you can specify the region (ROI) where the most detail should be preserved, minimizing the compression (and loss of detail) in that area.
GIF (Graphics Interchange Format) is a file format commonly used to display indexed-color graphics and images in hypertext markup language (HTML) documents over the Internet. GIF is an LZW-compressed format designed to minimize file size and electronic transfer time. The GIF format preserves transparency in indexed-color images; however, it does not support alpha channels.
TIFF (Tagged Image File Format) files are lossless, meaning that they do not degrade in image quality when repeatedly opened and closed. This is a very flexible image format supported by virtually all painting, imageediting, and page-layout applications. Also, virtually all desktop scanners can produce TIFF files. Photoshop can save layers in a TIFF file; however, if you open the file in another application, only the flattened image is visible. Photoshop can also save annotations, transparency, and multi-resolution pyramid data in TIFF format.
PSD (Photoshop Document) is Photoshop’s native file format and the only format that supports most Photoshop features (other than the Large Document Format [PSB]). Due to the tight integration between Adobe products, other Adobe applications can directly import PSD files and preserve many Photoshop features. Saving a PSD file is worthwhile if complicated manipulations were performed in Photoshop; in the File Info section of a PSD file, all of the procedures will be documented in chronological order.
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