Pennsylvania Sportsmen Turn to PDF
(too bad they didn't turn to DjVu!)
by James Rile, PlanetDjVu, November 28, 2001
The maps are published in both a High Resolution PDF version and a Low Resolution PDF version.
Since I live and work in Chester County, Pennsylvania, I downloaded both high and low resolution PDF versions of the map for the state game lands in my county.
Here are the file sizes of these two files:
A close inspection of the high resolution version shows that the map image was created as a JPEG file prior to conversion to PDF, and was heavily compressed before the PDF conversion. Heavy compression in JPEG format produces pixel-averaging that results in distortion of text and lines. Following is a detail of the high-resolution map, illustrating this problem:
I took the high resolution version of this map and converted it to DjVu. Although I did not have the uncompressed JPEG file as input, the DjVu encoding itself served to remove most of the pixel-averaging from the image. Here is the same map detail coming from the DjVu file:
Not only is the DjVu file much clearer and of a higher quality than the high resolution PDF version, it is also much smaller. The same map in DjVu segmented format is only 0.162 MB, less than half the size of the low resolution PDF version!
All I can say to the Pennsylvania State Game Commission and the sportsmen who download, view and print these maps is... too bad they are not DjVu!
PDF High: 2.047 Mb 100%
PDF Low: 0.480 Mb 46%
DjVu High: 0.162 Mb 8%
(who says you can't have more for less...)
A comment about page orientation:
The map is landscape-oriented, but is saved in both PDF and DjVu formats in portrait orientation, so it can be printed that way. This is fine for printing, but who wants to read the map sideways on the screen?
The DjVu viewer makes it simple to rotate the map so you can read it, but in the Acrobat Reader you cannot rotate the map to read it. Another big plus for DjVu!