[Coco] [Color Computer] 1984 djvu conversion

[stinger30au]

--- In ColorComputer at yahoogroups.com, "jasonb1963" <jasonb1963 at ...> wrote:
>
> Hi Dez,
> 
> --- In ColorComputer at yahoogroups.com, "stinger30au" <stinger30au@> wrote:
> > i use gscan2pdf, open source app
> 
> From http://djvu.org/resources/whatisdjvu.php:
> 
> Over 90 percent of the information in the world is still on paper. Many of those paper documents include color graphics and/or photographs that represent significant invested value. And almost none of that rich content is on the Internet.
> 
> That's because scanning such documents and getting them onto a Web site has been problematic at best. At the high resolution necessary to ensure the readability of the text and to preserve the quality of the images, file sizes become far too bulky for acceptable download speed. Reducing resolution to achieve satisfactory download speed means forfeiting quality and legibility. Conventional web formats such as JPEG, GIF, and PNG [formats used by Adobe's PDF format] produce prohibitively large image files at decent resolution. As a result, Web site content developers have been largely unable to leverage existing printed materials.
> 
> DjVu (pronounced "déjà vu") is a new image compression technology developed since 1996 at AT&T Labs to solve precisely that problem. DjVu allows the distribution on the Internet of very high resolution images of scanned documents, digital documents, and photographs. DjVu allows content developers to scan high-resolution color pages of books, magazines, catalogs, manuals, newspapers,historical or ancient documents, and make them available on the Web.
> 
> [...]
> 
> DjVu typically achieves compression ratios about 5 to 10 times better than existing methods such as JPEG and GIF for color documents, and 3 to 8 times than TIFF for black and white documents.
> 
> Scanned pages at 300 DPI in full color can be compressed down to 30 to 100KB files from 25MB.. Black-and-white pages at 300 DPI typically occupy 5 to 30KB when compressed.
> 
> This puts the size of high-quality scanned pages within the realm of an average HTML page (which is typically around 50KB).
> 
> For color document images that contain both text and pictures, DjVu files are typically 5 to 10 times smaller than JPEG at similar quality. For black-and-white pages, DjVu files are typically 10 to 20 times smaller than JPEG and five times smaller than GIF. DjVu files are also about 3 to 8 times smaller than black and white PDF files produced from scanned documents (scanned documents in color are impractical in PDF).
> 
> In addition to scanned documents, DjVu can also be applied to documents produced electronically in formats such as Adobe's PostScript or PDF. In that case, the file sizes are between 15 to 20KB per page at 300 DPI.
> 
> [...]
> 
> One of the main technologies behind DjVu is the ability to separate an image into a background layer (i.e., paper texture and pictures) and foreground layer (text and line drawings). Traditional image compression techniques are fine for simple photographs, but they drastically degrade sharp color transitions between adjacent highly contrasted areas - which is why they render type so poorly. By separating the text from the backgrounds, DjVu can keep the text at high resolution (thereby preserving the sharp edges and maximizing legibility), while at the same time compressing the backgrounds and pictures at lower resolution with a wavelet-based compression technique. DjVu is used by many commercial and non-commercial web sites on the Web today.
> 
> End of excerpt.
> 
> Sorry to be a bit verbose, but I've highlighted the main features that DjVu format offers over its competition (PDF).  I understand the desire to use PDF because there are a lot more tools available for manipulating PDF documents than DjVu documents, but I think it's a mistake to say that PDF is better for archival purposes than DjVu.  I believe the opposite is true.  If you want archival grade images, then use DjVu format at 600DPI and you will preserve far more information (even the imperfections in the paper the page is printed on) than you would with a 300DPI PDF while at the same time winding up with a smaller (!) document in the end.
> 
> In any event, I am very grateful for all the hard work you are putting into scanning these old magazines and I don't mean to be argumentative at all.  I am just offering my opinions on the subject in the spirit of friendly suggestions.
> 
> I have downloaded all of the 1989 issues of Rainbow and converted them to DjVu format.  I am considering uploading them to excalibur if there is any interest.  I have just used 300DPI myself because this looks comparable to the original PDFs at 300DPI to my eyes so far.
> 
> --
> Jason
>


im not getitng in to a debate over PDF or Djvu. 

im well aware of both formats and thier short falls.
im also quite handy at looking up this kind of info via google or other search engines as well.

the mean reason i investiaged djvu format was to decrese the size of the pdf files


this was done as there was some who said the files were too big


so i put forward the idea of posting what countries we lived in so those with slow net connections could contact us who posted out counties and get a set on dvd or the likes

i did this twice and only the 2nd time did others join in and post their countires.
the yahoo archive has history of this to show it.

it landed on "deaf ears" so to speak as to the best of my knowledge no-one has been approached for a set of dvd's

i wont be entering in to this debate any further.