Apr
28
I like to backup my important documents or briefs into my computer in PDF file type. But in my experiment using a scan in Ubuntu is not easy as in Windows System.
The gscan2pdf is a GUI program to directly create a multipage PDF from a scan. It should work on almost any Linux/BSD system.
How to install the gscan2pdf in Ubuntu or Debian-based system
First you need to add the following line to your /etc/apt/sources.list file:
deb http://gscan2pdf.sourceforge.net/download/debian binary/
Then you need to update the source list with the following command:
apt-get update
Now you can install gscan2pdf with the following command:
apt-get install gscan2pdf
I use a simple scan Canon CanoScan N655U. I test gscan2pdf to scan a color and a normal A4 form pages with different scan model and dips. I become the following results:
At first, we should know what does dpi mean and how much dpi is enough.
For copying text to the printer, or for OCR, use 300 dpi and Line art mode is a very good ideal. Line art mode is 1-bit 2-color (Black & White) . Since there is no Gray, the printer can use its full resolution and can print 300 dpi. If a 600 dpi printer, then you can scan at 600 dpi. Since Line art mode is only 1/24 the memory size of color, we can handle the large image without much pain. Frankly, 300 dpi scans of most text documents look fine on a 600 dpi laser printer, and more scan resolution is not often very useful (but the highest quality requirements should print 600 dpi line art).
So note that this is suddenly a new tune we’re singing. For Color or Grayscale scans, you have little (if any) reason to ever approach 300 dpi. For Line art scans however, including OCR, you’re probably always at 300 dpi. I’ve made the assumption that we are printing these images. For display on a video monitor, then 300 dpi is probably too large to be useful.
More information you can see website http://www.scantips.com/. There have more detail descriptions and discuss about text and photo scan for different uses.
Following are my test:
For color document:
using color model, dpi 120 to 150 - optimal file size and good quality.
For white & black text document:
using linear(white & black) model, dpi 300 - small file size and very good quality.
using linear(white & black) model, dpi 600 - little big file size and perfected quality.
using grayscale model, dpi 150 - big file size and normal quality.
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Very good article, i need it.
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