On 12/4/06, Alfio Puglisi <alfio.puglisi(a)gmail.com> wrote:
In the
resulting image, now 200 kbytes, every 150 pixels
correspond to one inch of the printed page, from which it was
originally scanned. Thus, I'm using the shorthand terminology
that this is now a 150 dpi image. Since most computer screens
have a resolution in the rage 100-120 dpi, this means the image is
displayed a little "larger than life".
Ah ok, now I understand what you are trying to do.
TIFF G4 seems actually the best format for these kind of images,
regardless of the dpi setting. PNG can store 1 bit images, but even at
the maximum compression level (9) the full 3616x5550 image is about
380 kbytes instead of 200.
No. Dejavu is, by a mile.
[gmaxwell@floodlamp ~]$ cjb2 -losslevel 100 nfad-0670.tif nfad-0670.djvu
[gmaxwell@floodlamp ~]$ ls -l nfad-0670.*
-rw-rw-r-- 1 gmaxwell gmaxwell 72075 Dec 4 21:55 nfad-0670.djvu
-rw-rw-r-- 1 gmaxwell gmaxwell 200865 Dec 4 08:01 nfad-0670.tif
[gmaxwell@floodlamp ~]$ cjb2 -lossless nfad-0670.tif nfad-0670.djvu
[gmaxwell@floodlamp ~]$ ls -l nfad-0670.*
-rw-rw-r-- 1 gmaxwell gmaxwell 128772 Dec 4 21:56 nfad-0670.djvu
-rw-rw-r-- 1 gmaxwell gmaxwell 200865 Dec 4 08:01 nfad-0670.tif
[gmaxwell@floodlamp ~]$ cjb2 -losslevel 200 nfad-0670.tif nfad-0670.djvu
[gmaxwell@floodlamp ~]$ ls -l nfad-0670.*
-rw-rw-r-- 1 gmaxwell gmaxwell 35209 Dec 4 21:56 nfad-0670.djvu
-rw-rw-r-- 1 gmaxwell gmaxwell 200865 Dec 4 08:01 nfad-0670.tif
Even at losslevel 200 zoomed way in, I'd be hard pressed to tell the
original from the djvu. Djvu lossy works by reusing whole
characters... so it should not adversely impact OCR, although it does
not work so well on noisy documents. Even in lossless mode djvu is
half the size of the tiff.
The free software djvu viewer is very good, easily better than most of
the PS and Tiff viewers I've used.
Djvu can also produce mixed pages of images and text using the optimal
compression method for each type. You can't do that with TIFF in G4
mode. Djvu's lossy compression of photographic material is vastly
superior to jpeg (more quality per bit in terms of PSNR, and less
objectionable artifacts at low quality levels). Djvu files can also be
loaded incrementally.. loading more data as you zoom in. Great for
high resolution images like satellite photography or other ridiculous
resolution photographs.