Ease of Use

Efficiency

Interoperability

Quality

Reliability

Versatility

Quality

The BitJazz compression engine and the PhotoJazz image file format always maintain perfect fidelity. No matter how many times you compress and decompress an image with PhotoJazz, the final image is always bit-for-bit identical with the original image. In contrast, JPEG, the most popular image compression format for photo-quality images on the web, always degrades the image quality, even at the highest quality setting. (See "JPEG Lossiness" for discussion and examples).

For convenience in viewing, the QuickTime decompressor component in PhotoJazz QT will scale an image to any size and convert the image to the viewer's color space. In general, it is theoretically impossible for such scaling and color conversion operations to maintain perfect fidelity, and PhotoJazz QT is no exception. However, PhotoJazz QT uses a special scaling filter to minimize the loss in fidelity while maximizing the quality of the scaled image.

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Efficiency

For photo-quality images, PhotoJazz achieves the highest compression power of all perfect-fidelity image compressors on the market by a large margin (see "BitJazz Lossless RGB Image Compression Statistics" for details). Based on tests using standard images from Kodak, PhotoJazz's average compression power for photo-quality RGB images is 2.5. In comparison, TIFF-LZW averages 1.6 on the same set of images, and PNG averages 1.8. For example, BitJazz typically compresses a 4.5 MB, 1536x1024-pixel photo-quality RGB image down to just 1.8MB, which takes 14 minutes instead of 35 to transmit over a 28.8Kbps modem line.
For poster-quality images, BitJazz's compression power is much higher, averaging about 10, with a maximum of over 1000. However, other compression methods, such as PNG, are usually better for poster-quality images.

The PhotoJazz engine's speed is quite fast, compressing about 1MB per second on a 266MHz G3 computer. That's about three times as fast as PNG. Naturally, the PhotoJazz engine's performance does improve with faster CPUs, faster and bigger caches, and faster disk drives.

By tiling the image, PhotoJazz's memory requirement is small and constant, irrespective of the size of the image being compressed or decompressed. Tiling also permits progressive display and random access for large images.

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Reliability

To maintain the highest reliability, the PhotoJazz image file format incorporates CRC (cyclic redundancy checking) for state-of-the-art data integrity verification. Every single bit of information in a PhotoJazz image file is safeguarded by data integrity verification, so that the PhotoJazz plug-in and other components of BitJazz Tools can inform you at the earliest opportunity if the PhotoJazz image file has been corrupted, whether due to storage medium failure or transmission errors. Since the most common transmission errors are actually protocol errors, the PhotoJazz image file header contains special safety bits to detect the most common protocol errors right up front, including linebreak mangling, byte decapitation, null-character deletion, and delete-character deletion. If PhotoJazz detects a protocol error, you should check the protocol settings at each transmission stage to locate and correct the problem(s), and then retransmit the image. If PhotoJazz detects an error later on in the file, you should run Disk First Aid or equivalent disk repair utility to check for and repair bad blocks or other problems with your disk, and then retransmit the image or restore it from a backup version.

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Versatility

Image dimensions are unlimited in the PhotoJazz engine and the PhotoJazz image file format. However, the Photoshop File Format interface limits the size of images to 30000 pixels on a side, so applications such as Adobe Photoshop that use the PhotoJazz plug-in cannot handle PhotoJazz images greater than that limit. QuickTime also limits the image size, but its limits are so large (2 147 483 647 pixels on side) that they are not likely to hamper many users in the near future.

PhotoJazz supports all high-quality color models, including perceptual models such as L*a*b*; light-based additive models such as monochrome, RGB, and multispectral; and pigment-based subtractive models such as grayscale, CMYK, duotone/tritone/quadtone, hexachrome, and high-fidelity. Low-quality color models (i.e. indexed-color and bilevel) are not directly supported by PhotoJazz, but indexed-color and bilevel images can readily be compressed by PhotoJazz when converted to RGB and grayscale, respectively.

Pixel depths of up to 255 channels are supported by PhotoJazz, including any number of primary, spot-color, and alpha channels. This is far more than either the Photoshop File Format interface or the QuickTime Still Image interface can handle. Photoshop limits the total number of channels to 24.

The channel precision supported by the PhotoJazz engine, the PhotoJazz image file format, and both PhotoJazz and PhotoJazz QT is up to 16 bits per channel. QuickTime and QuarkXPress also support 16 bits per channel for some color models. Photoshop nominally supports 16 bits per channel for some actions on some color models, but its actual maximum precision is just a hair over 15 bits.

The PhotoJazz image file format also supports non-image data, including embedded ICC Profiles and application-specific data.

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Interoperability

PhotoJazz is a cross-platform product, currently available for both Power Macintosh and Windows . The PhotoJazz image file format is completely interoperable between Macintosh and Windows. The PhotoJazz QT QuickTime components can be used directly by any application supporting QuickTime's Still Image or Movie protocols, and indirectly by any application supporting QuickDraw Picture (PICT) files or QuickTime Image (qtif) files. The PhotoJazz Photoshop plug-in can be used by any application supporting Photoshop's File Format plug-in interface. The PhotoJazz XT QuarkXTensions module can be used by QuarkXPress.

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Ease of Use

PhotoJazz has the simplest, most-streamlined user interface possible: None. It just works the way you expect it to.

BitJazz Inc. offers, free of charge, a complete software development kit (SDK) permitting any applications developer to access PhotoJazz image files and the PhotoJazz engine directly.

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