Municipal World Case Study
Municipal World has an illustrious 109 years of continuous publication history. The publication started as black and white text and has evolved to the full-color sample used in this study. This 32-page sample was published in February 2000.
The purpose of this study is to demonstrate how this publication can be rendered into digital surrogate files for delivery on the web. By the term "digital surrogate", we mean a digital document file that preserves all the information of the paper copy, while also adding the intelligence that is possible only in digital format. We also mean a document that can be effectively delivered on the web, given todays 56K to 128K bandwidth threashold.
Six formats for the "digital surrogate" are considered and demonstrated in this case study:
DjVu Image Only - 300 dpi (1.22MB)
DjVu Image + Hidden Text - 300 dpi (1.35MB)
LuraDocument - Image Only - 300 dpi (4.04 MB)
All of the formats in this study were produced with full-color JPEG images, with a resolution of 300 dpi and a compression level of 80%. The average page image size is 1.38 MB. Lizardtech has subsequently recommended a more conservative compression level of 95% for use with DjVu, but said that these particular images produce good results at the 80% level.
The 200 dpi version of this 32-page issue is beautiful to look at and to print, and it has OCRed text just like the DjVu I+T version. The problem is that it is 17.4 MB. This is an average page size of 1.8 MB! No problem on a hard drive, but on the internet this is way too large.
Downsampling to 100 dpi produces too much pixel-averaging which distorts the image of the text, so this is not acceptable for display and print. Downsamling to 150 dpi seems the best resolution for the tradeoff between image quality and file size.
The size of the 150 dpi version is 12.5 MB, and the size of the 100 dpi version is 7.8 MB. These are too large for effective web delivery.
The DjVu Image Only version and the version with hidden text were created with DjVu Workgroup 3.0, using the "maximum text quality" setting.
DjVu is a clear winner for best size, best display and best printing.
The LuraDocument version is a multipage document with a total size of 4.04 MB. It was created with LuraDocument Capture 1.01 LE using the Catalog encoder setting.