ProJPEG‚Ñ¢ is the most powerful tool available for creating optimized JPEG files for the web. It has many advanced features that make producing JPEG files easy and efficient with no surprises in store.
ProJPEG‚Ñ¢ is an Adobe Photoshop 3.0 File-Format plug-in that integrates seamlessly into Adobe Photoshop. It combines open and save simplicity with the most powerful features available for creating JPEG files.
What is JPEG?
JPEG (pronounced ‘jaypeg’) is the common usage name of one of two graphic file formats commonly supported by web browsers. Note, that JPEG is a compression method and not the actual name of the file format. JFIF is the correct name of the file format that web browsers support.
JPEG and the JFIF format were developed by the Joint Photographic Experts Group to provide for efficient compression and storage for full-color and gray-scale, continuous tone images of natural, real world scenes, i.e. photographs. JPEG, referring to the common name of the format, supports 24-bit color (16.7 million colors) and uses JPEG compression, which is a ‘lossy’ method, meaning that image data is lost in the compression process, and the uncompressed image will not match the original image perfectly, as it would if it were compressed with a ‘lossless’ method. JPEG is highly optimized for compressing continuous tone, photographic images and does not perform as well, both in terms of resultant visual image quality and in terms of achievable compression, for other types of images. Generally, you should not use JPEG for images that are not photographic in nature.
Installing ProJPEG‚Ñ¢
To install ProJPEG™ simply place the ‘ ProJPEG™ 2.1’ plug-in inside your Adobe Photoshop ‘Plug-ins’ folder and optionally inside the ‘File Formats’ folder within the ‘Plug-ins’ folder. ProJPEG™ will then be available to use as a method to open and save files the next time Photoshop is launched. ‘ ProJPEG 2.1’ will then appear as a new item in the file format menu in Photoshop’s open file and save file dialogs.
 
ProJPEG‚Ñ¢ is a FAT plug-in and will run in native mode on both 68k and PPC based Macintosh computers for best performance.
Key differences between ProJPEG™ and Photoshop’s JPEG
There are key differences between ProJPEG‚Ñ¢ and Adobe JPEG. Adobe JPEG implements non JFIF compliant extensions to the format that ProJPEG‚Ñ¢ does not support, specifically CMYK JPEG files as these are not suitable for web use and not supported by web browsers. ProJPEG‚Ñ¢ also supports JPEG variations that Adobe JPEG does not, specifically progressive JPEG files.
This can cause some confusion when attempting to open existing CMYK JPEG files that you created with Adobe JPEG using ProJPEG‚Ñ¢, and also when attempting to open progressive JPEG files that you created with ProJPEG‚Ñ¢ using Adobe JPEG.
ProJPEG‚Ñ¢ will report correctly that a CMYK JPEG file is an unsupported file type, however Adobe JPEG will incorrectly report a progressive JPEG file as being corrupt and damaged.
If you encounter a JPEG file that creates and error when attempting to open it using either ProJPEG‚Ñ¢ or Adobe JPEG first try opening the same file using the other method before assuming that the file may actually be corrupt.
