Newbie Question: getting small file sizes with good image quality

F

Freep

Hi
I am new to scanning and would like advice about how to minimize
file size while trying to presere image quality. I have some
genealogy documents that I would like to share with distant cousins
that I have met online and would like to minimize the file size so
that that can more easily share and store the documents; yet image
quality is most important.

My current routine is to scan the documents at maximum resolution and
color which creates a bitmap which is about 98,000k
I then use Irfanview to reduce the resolution so that the smaller
dimision (usually width) is between 500 and 1000 pixels. I do this
by reducing the giant bitmaps's and higth and width by some factor of
2. Finally I save the image as a jpg and set preserve image quality
at 50%
The resulting jpgs are usually between 100k and 300k

Anyone know of a better method to keep file sizes relatively small
while preserving document qualitiy??

Thanks In Advance!
Fearless Freep
 
D

Dances With Crows

I am new to scanning and would like advice about how to minimize file
size while trying to [preseve] image quality. My current routine is
to scan the documents at maximum resolution and color which creates a
bitmap which is about 98M.

Silly. If this stuff is on paper, you won't gain much by going past 300
DPI, 600 at the very highest if the text/graphics have a lot of detail
(as you'd find in Japanese text.) 98M is insane.
I then use Irfanview to reduce the resolution so that the smaller
[dimension] (usually width) is between 500 and 1000 pixels. I do this
by reducing the giant bitmap's [height] and width by some factor of
2. Finally I save the image as a [JPEG] and set preserve image quality
at 50%

Downsampling like that will reduce detail and take a long time for an
image that large. JPEG means lossy compression. If you're OK with
that, fine, but you have to realize what it means and be prepared to
deal with the consequences. Setting quality at 50 instead of the usual
default (75) will introduce noticable artifacts in many cases.
Anyone know of a better method to keep file sizes relatively small
while preserving document [quality]?

If I were you, I'd scan at a lower initial DPI and compress with Group4
(black-and-white) or LZW (color/grayscale) TIFF. Both compression
methods are lossless, and Group4 is insanely efficient. A 17x22"
newspaper page at 300 DPI black-and-white compressed with Group4 comes
out to ~600K. An 8.5x11" page at the same DPI is about 60K. If your
final use for these images is viewing onscreen, JPEG will work, but if
you ever want to print these things out on a good printer or manipulate
them in an image editing program, you're going to want lossless
compression--otherwise the artifacts JPEG introduces will make the final
results look a bit flaky.

Somebody will no doubt say something about http://scantips.com/ at some
point. Read and understand that; it may help.
 
M

MikeD

If I were you, I'd scan at a lower initial DPI and compress with Group4
(black-and-white) or LZW (color/grayscale) TIFF. Both compression
methods are lossless, and Group4 is insanely efficient.

I agree 100%. I save all my scanned genealogy stuff this way. G4 TIFF
handles multiple pages, so it's ideal for documents.

If you want to create more compact portable files for emailing to others,
then you can use the full version of Acrobat to import the TIFF and create a
PDF. It will convert the graphics to JPG, but that's OK for onscreen
viewing.

Mike
 
F

Freep

I agree 100%. I save all my scanned genealogy stuff this way. G4 TIFF
handles multiple pages, so it's ideal for documents.

Thanks guys!

Do either of you know whether or not the "CCITT Fax 4" compression
method which appears as an option in Irfanview's Save As (tiff)
dialogs is the Group 4 you guys are talking about?

Is Irfanview a good tool or do you recommend other software?

Thanks Again!
Fearless Freep
 
D

Dances With Crows

? The TIFF standard says that TIFF supports multiple pages. The
compression method used on individual pages within the file shouldn't
matter, and it can be different for different pages. The main thing to
watch out for is software that can't handle multipage TIFFs; most
programs do, but there are a few that don't. The "Imaging" application
that comes with Windows will handle multipage TIFFs, but it won't handle
RLE, PackBits, or JPEG-compressed TIFFs. Go figure.
Do either of you know whether or not the "CCITT Fax 4" compression
method which appears as an option in Irfanview's Save As (tiff)
dialogs is the Group 4 you guys are talking about?

That's another name (the official name) for Group4.
Is Irfanview a good tool or do you recommend other software?

I use Gimp and ImageMagick (Windows/OS X ports at http://gimp.org/ and
http://imagemagick.org/ ) for interactive image editing and scripted
image editing, Kuickshow for viewing images. If Irfanview works for
you, that's all that matters. HTH,
 
R

RSD99

First:
IrfanView *can* 'Save As...' in the TIFF CCITT Group 3 and Group 4 FAX
formats ... but *only* for B&W images.

Second:
You asked "... Is Irfanview a good tool or do you recommend other software?
...."

IrfanView is an *excellent* tool, and is recommended. This is not to say
that there are no other programs that you should have and use, just that
you should have IrfanView to complement your other programs.
 
D

Dances With Crows

IrfanView *can* 'Save As...' in the TIFF CCITT Group 3 and Group 4 FAX
formats ... but *only* for B&W images.

Group3 and Group4 can only handle black-and-white images. This is by
design. For grayscale stuff, you might get the best results by scanning
it in as grayscale, fiddling with the brightness/contrast/whatever
until it looks good, saving it as grayscale, and doing something like:

convert -monochrome -compress Group4 file.tif temp.tif
rm -f file.tif
mv temp.tif file.tif

....convert is part of ImageMagick. Gimp won't save as Group4, Photoshop
might if you set the palette to "indexed" and "black and white". You
can also use tiffdither from the tiffutils package, but IME convert does
a better job even though tiffdither is faster.
you should have IrfanView to complement your other programs.

Yeah, pick the right tool for the job. If you find one program that
does everything, it probably does everything poorly.
 
R

Rob Seefer

I use a small scanning utility from Autumna Software
(http://www.autumna.com) that does it in one step:

- I scan directly and save into multipage G4 Tiff (excellent compression
rate for B&W)
- Later if I want to output to PDF, I'll do an "import" of the TIFF file
into the app, remove unwanted pages and save as PDF.
- Color scans are saved as TIFF single/multipage with LZW compression (no
quality loss)

Rob.
Cheers.
 

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