Top Document: JPEG image compression FAQ, part 2/2
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Most Mac JPEG programs rely on Apple's JPEG implementation, which is part of the QuickTime system extension; so you need to have QuickTime installed. To use QuickTime, you need a 68020 or better CPU and you need to be running System 6.0.7 or later. (If you're running System 6, you must also install the 32-bit QuickDraw extension; in later Systems, that is built in.) The latest officially released version of QuickTime is 3.0, available from http://www.apple.com/quicktime/. QuickTime 3.0 can read progressive JPEGs (but not write them). Older versions of QuickTime can't handle them at all, and are also more likely to crash if fed a corrupted JPEG. If you're using QuickTime-dependent programs to handle JPEG then I recommend upgrading to 3.0 pronto. (Note that many of the programs recommended in this section contain their own JPEG codecs and don't depend on QuickTime.) Mac users should keep in mind that QuickTime's JPEG format, PICT/JPEG, is not the same as the Usenet-standard JFIF JPEG format. (See part 1 for details.) If you post images on Usenet, make sure they are in JFIF format. Most of the programs mentioned here can handle either format. The largest Internet collection of Mac software is the Info-Mac archive, which is mirrored in many places (the master site is only directly accessible by the archivists themselves). The pointers below cite Apple Computer's mirror site, but you may get better service from a mirror site closer to you. See "Introductory Macintosh Frequently Asked Questions" in the comp.sys.mac.* newsgroups for the current locations of mirrors. JPEGView is an excellent free program for viewing JFIF,PICT/JPEG,GIF,TIFF, and other image files. It can convert between JFIF and PICT/JPEG and can create preview images for files. The current version is 3.3.1, available from http://www.umich.edu/~archive/mac/graphics/graphicsutil/jpegview3.31.sit.hqx. Requires System 7; QuickTime is optional. JPEGView is a fine viewer with an unusual but well-thought-out design (no scroll bars, for example). Unfortunately, it hasn't been updated in a long time, and is starting to show its age. There are reports of bugs under System 7.5.3 and later. Also, its built-in JPEG decoder doesn't know about progressive JPEG. If you like JPEGView, I suggest installing QuickTime 3.0 and setting JPEGView to use QuickTime. Jade is a new, very promising freeware viewer for JPEG, GIF, PICT, and BMP images. It's fast, simple to use, and has preview and slideshow capabilities. And it supports progressive JPEGs. Since JPEGView is no longer being updated, Jade will probably supersede it as the most popular free Mac JPEG viewer before long. Current version is 1.2, available from ftp://mirror.apple.com/mirrors/Info-Mac.Archive/gst/grf/. Requires 68020 (or higher) or PowerPC, as well as System 7.5 (or later) or Thread Manager. GIFConverter, a shareware ($30) image viewer/editor/converter, supports JFIF,PICT/JPEG,PNG, and many other image formats. Current release is 2.4.4, available from http://www.kamit.com/gifconverter/. Requires System 6.0.5 or later. GIFConverter is not better than JPEGView as a plain JPEG/GIF viewer, but it has much more extensive image manipulation and format conversion capabilities. Also, GIFConverter is your best bet if your machine is too old to run System 7 and/or QuickTime. Hint: if GIFConverter runs out of memory while loading a large JPEG, try converting the file to GIF with JPEG Convert, then viewing the GIF version. GraphicConverter is another popular viewer/editor/converter. It has even more functionality than GIFConverter, but is correspondingly larger. Great if you like lots of options. Shareware, $35. Current version is 3.6, available from the author's website http://www.lemkesoft.de/ or various mirrors. Sam Bushell has prepared a couple of simple but nicely done drag-and-drop converter applications, "To JPEG" and "Progressify". To JPEG converts any file format understood by QuickTime to regular or progressive JPEG; Progressify converts losslessly between regular and progressive JPEG formats. Both are free and require System 7.0 or later. Available from http://www.pobox.com/~jsam/to-jpeg and http://www.pobox.com/~jsam/progressify. Cameraid is a useful utility program designed for users of digital cameras, but having general interest as well. It does image downloading from many makes of digicam, lossless rotation and other transformations of JPEGs, and display of auxiliary information that many digicams include in their JPEG output files. It's also a nice viewer. Version 1.1.1 is available from http://www.clinet.fi/~jmunkki/cameraid/. Shareware, $15. Photoshop 4.0 supports progressive JPEG. If you have an older version, you can get two different plugins that enable progressive JPEG support (they also work in other applications that support Photoshop plugins). One is ProJPEG, available from ftp://ftp.boxtopsoft.com/pub/ (shareware, $25). The other is JPEG Transmogrifier's plugin version, available from http://www.in-touch.com/jpeg.html (shareware, $22). ProJPEG is worthwhile even with PS 4.0, because it has a nifty preview of the results of different compression settings. HINT: You must set the file type code of a downloaded JPEG file to 'JPEG' to allow Photoshop to recognize it. Most of the other programs suggested here are not so picky about file type codes. HINT: if you use Fetch to retrieve files by FTP, make sure ".jpg" is in its list of binary file types under Customize/Suffix Mapping. Otherwise Fetch's "automatic" retrieval mode will retrieve JPEGs in text mode, thus corrupting the data. Old versions of Fetch do not include ".jpg" in the default list. Also, Fetch 3.0 is buggy; get 3.0.1 or later for reliable uploads.