Chapter 4 – Image Preparation

Some of the information in the section is directed at the 'non-graphic' people involved the catalog design process. However, we recommend that everyone involved read this chapter as it contains necessary and useful information. 

Item Images

The filenames for all of the items in the catalog need to match the item number set up in the Inventory Program in EZZ.  This is the only way for any tags in the templates to reference item-related information in the back end.  For any items that require more than one image, (i.e., a ShortList image and a Details image), use a single character before the item number to differentiate between them.  For example, the Discover Clock is item number DC144.  The ShortList image filename should be DC144 and the Details image filename should be dDC144.

100x100 pixel. is a good size for the ShortList image, and 300x300 is a good size for the Details image.  However, this does depend on the catalog and layout.  You may find that you do not require a both images.  You may find that you need more than two images.  Again, this depends on the catalog.  The graphics package we use is Photoshop 5.5.  It is the industry-standard package, and we have been very pleased by the results it produces.

We have found that it is best to start with a digital image, either a BMP or a vector-based graphic.  If that is not viable for your company, then scanned images work fairly well.  It is best to start with a high-resolution (150+dpi), large image and size it down as necessary. 

Following is a list of commonly used image file types and their definitions, advantages, and disadvantages.  We hope that you will find it useful in answering any questions you may have about the various types of images.

JPEG

The JPEG (Joint Photographic Experts Group) is a standardized graphics format. The standard was developed for compressing raw, digital, photographic information depicting real world or realistic "photographic" scenes. This includes paintings, photographs, textures, etc.  JPEG compression economizes on the way data is stored and also identifies and discards "extra" data, that is, information beyond what the human eye can see. Because it discards data, the JPEG algorithm is referred to as "lossy."

JPEG allows for substantial compression of file size. In addition, using JPEG allows the storage of pictures at a much higher color resolution. This allows for greater accuracy and better-looking images.

One of the problems with JPEG is that it is a "lossy" compression format. If you begin with a raw image such as a TIFF or BMP, all of the digital information exists. However, when you compress the information using JPEG, some of the information is lost. When the picture is reconstructed, the decompression approximates what the original picture contained. Usually this can be quite good. However, sometimes pictures experience "artifacting" where sharp edges become jagged and smooth textures start looking ragged. One advantage of JPEG compression is that you can select the quality when compressing the image. However the tradeoff here is the amount of space required.  The lower the quality, the smaller the image, but the more different it will appear than the original.

Use JPEG for compressing large pictures that are originally scanned as TIFFs or BMPs. Don't use JPEG for compressing line drawings. Instead, use GIF or PNG.

GIF

The GIF (Graphical Interchange Format) has been around since 1987. This format was designed to deliver high-resolution images over the Internet.  One problem back in 1987 was the relatively low transmission rates over the Internet. So to decrease the waiting time for images to come across the Internet, the people at CompuServe devised a compression scheme for BMPs. The CompuServe GIF format is a highly compressed format (using LZW compression) that is designed to minimize file transfer time over phone lines. GIF format only supports color-mapped images with less than 8 bit color.  The GIF compression unlike JPEG compression is non-lossy. It uses a proprietary encoding/decoding scheme called LZW. A GIF file consists of a header and the encoded data. When you view the image, the software uses the LZW scheme to decode the file into a BMP for display. Similarly, when you save a BMP as a GIF, the BMP is encoded and compressed. This compression works well and led to the popularity of the GIF format. In 1989, CompuServe enhanced the old 1987 format with a few new features. Of primary interest were the "interlaced" and the "transparent" features. Additionally, the GIF format was further enhanced so that an experienced user could "string" a bunch of GIF s together in the form of an "animated GIF" and keep them all in the same file. These features were well timed for the Internet explosion and fit nicely with the new World Wide Web navigation software.

GIFs are very Internet compatible because of their small size and special features. They are the most common format for buttons, icons, and horizontal rules in HTML documents. Additionally, the interlacing features allow a document to be downloaded and have the image displayed progressively. Lately, the animation capabilities of GIFs are used for spicing up web pages in all kinds of interesting ways, from the ubiquitous stuffing envelope to raging tornadoes.

GIF is an Internet friendly format that is useful for icons, buttons, horizontal rules and simple line drawings and cartoons, GIF89a is the latest version of GIF and it supports basic animation and interlacing. Essentially, GIF is best for simplistic image is with few colors. If you want to present photographs go with JPEG on the Internet or TIFF if you want a non-lossy format.