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making big GIFs and little GIFs

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February 8, 2005 1:40:50 AM

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

How do I scan a map to a GIF so that when I view the GIF file at its
"normal" size it is a maginification of the original.

In other words, what took one inch in the original document now takes
1.5 inches in the GIF at its normal size.

----

OTHER INFO ... I have tried to do this with my Epson Twain settings
but I seem to end up with a lower resolution (even though the
resoultion setting is kwpt the same).

When I have a resizing utilities (like Pic2Pic) on a GIF file I seem
to get a quite noticeable drop in quality. Is this inherent in
resizing a GIF? Is it better to use a different image format such as
TIFF, PNG, JPG in order to enlarge the image after scanning?

More about : making big gifs gifs

Anonymous
February 8, 2005 1:40:51 AM

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

Franklin wrote:

> How do I scan a map to a GIF so that when I view the GIF file at its
> "normal" size it is a maginification of the original.
>
> In other words, what took one inch in the original document now takes
> 1.5 inches in the GIF at its normal size.

You have to know the resolution in dots per inch of your monitor.

To find this resolution, grab a ruler and measure the width of the
image on your monitor. (Be careful not to scratch it).

Next find what resolution your video card is set to.

In Windows, right click on the desktop -> choose 'Properties'
When the dialog box pops up, click on the 'Settings' tab.

Here, you'll see your screen resolution listed in pixels. There
will be a bar you can slide to the left or right to change it.

From the physical width and resolution in pixels, you can calculate
how many pixels per inch, PPI (or dots per inch DPI) your monitor
displays.

For example:

- My laptop screen measures 12 inches across.

- The screen resolution is 1024 x 768 pixels.

To calculate the horizontal DPI I divide the physical size by
the resolution. So... 1024 pixels / 12 inches = 85.33 DPI
or if we round off, my laptop LCD panel displays 85 DPI.

This means an image 85 pixels wide will be exactly one inch
wide on my monitor. An image 85x2 pixels wide (170 pixels)
will be exactly 2 inches wide.

You can follow this up to an image 1024 pixels wide.. This will
fill the full 12 inches of the screen completely. Images of
over 1024 pixels will scroll off the edge.

You don't have to scan at this DPI.. Just scale the image
after the fact. Usually it's better to scan at higher
resolutions then scale down to fit.

In my case (with my 85 DPI monitor).. If I scan a 6 inch wide
document, and I want to see it take up 6 inches of my screen, I
just have to make sure it's 6" x 85 DPI = 510 pixels across.

Note that there are so many monitor sizes and video resolutions
in use, there is no way you can size an image to fit all monitors.

For example, if someone has a 12 inch wide monitor set to 800 x 600
pixels rather than 1024 x 768 pixels , then his/her horizontal DPI
will be 800 pixels / 12 inches = 66 DPI.

The 510 pixel image that was 6 inches on an 85 DPI screen will
appear larger.. (510 pixels / 66 DPI) = 7.7 inches on a 66 DPI screen.
Anonymous
February 8, 2005 1:40:51 AM

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

In article <95F6E6B89D09271F3M4@130.133.1.4>, no_thanks@mail.com
says...
>
>
>How do I scan a map to a GIF so that when I view the GIF file at its
>"normal" size it is a maginification of the original.
>
>In other words, what took one inch in the original document now takes
>1.5 inches in the GIF at its normal size.
>
>----
>
>OTHER INFO ... I have tried to do this with my Epson Twain settings
>but I seem to end up with a lower resolution (even though the
>resoultion setting is kwpt the same).
>
>When I have a resizing utilities (like Pic2Pic) on a GIF file I seem
>to get a quite noticeable drop in quality. Is this inherent in
>resizing a GIF? Is it better to use a different image format such as
>TIFF, PNG, JPG in order to enlarge the image after scanning?



You said View, so I am assuming you want to view it on the video
screen, instead of printing it. The best way (highest quality) to
enlarge it on the video screen is to scan it again at 50% greater
resolution. That will create 50% more pixels in each dimension, and so
it will view on the screen at 50% larger size.

Or you could resample an existing image to be 50% larger, but yes, that
will loose quality. If you can scan it, then scan it.

For the video screen, GIF is NOT the problem, GIF is desiged for the
video screen. Certainly GIF is not the SIZE problem on the screen.
GIF is limited to 256 colors, a problem for photographs, but this is
surely no problem for a map. Probably you could even reduce it to 16
colors for a smaller file without losing anything (but there are always
some ifs and buts, I dont know what you have). Or you could use TIF or
PNG, also very fine if you can use them. I would try hard NOT to use
JPG for a map, quality suffers.

The size problem might be because there are no inches in the video
system, meaning that you cannot work in inches for the video screen.
Your video screen is instead dimensioned in pixels, for example perhaps
1024x768 pixels is a common size.

I dont know the size of your map, so I am making up numbers, but if for
example, you scan a 6 inch paper map dimension at say 100 dpi, you will
create 6x100 = 600 pixels of image dimension. This will fill 600
pixels of your 1024 inch screen dimension. Regardless, more resolution
is a larger image, less is smaller (on the video screen - printing
works rather differently).

Or per your question, if you instead scan this example at 150 dpi (50%
more) it will create 900 pixels which will fill 900 pixels of your
screen dimension, and it will appear 50% larger on the screen than the
100 dpi image.

--
Wayne
http://www.scantips.com "A few scanning tips"
Related resources
February 9, 2005 9:54:14 AM

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

> Franklin wrote:
>
>> How do I scan a map to a GIF so that when I view the GIF file
>> at its "normal" size it is a maginification of the original.
>>
>> In other words, what took one inch in the original document now
>> takes 1.5 inches in the GIF at its normal size.

On 08 Feb 2005, Jim Townsend wrote:
>
> You have to know the resolution in dots per inch of your
> monitor.
>
> -- snip --
>

Jim, thank you for a detailed reply. My need is also to **print**
the GIF (which is of a text document) at normal size as well as to
view it at normal size on the PC screen.

Let me explain some more .... My experience is that if I shrink or
enlarge a GIF then even if the change in size is relatively small
then the new GIF can be seen on the screen to be of noticeably lower
quality.

In your reply you have explained more about this and told me how to
predict dimensions and to accommodate dpi settings. But what about
PRINTING?

If I were then to print the GIF image I view on the screen then I
reckon it would probably print just as badly if not even worse than
what can be seen.

So I figure that I should print the GIF at its "normal" size in order
to avoid any noticeable reduction in quality. As my original post
here mentions, I have tried to do this by (1) changing Twain settings
as well as by (2) using resizing utilities. But I have had poor
results. Maybe I am not using these applications correctly?

As an alternative approach, perhaps there are image file formats
which are better suited to resizing operations than GIF is?
Anonymous
February 9, 2005 1:28:47 PM

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

Franklin wrote:


> Jim, thank you for a detailed reply. My need is also to **print**
> the GIF (which is of a text document) at normal size as well as to
> view it at normal size on the PC screen.
>
> Let me explain some more .... My experience is that if I shrink or
> enlarge a GIF then even if the change in size is relatively small
> then the new GIF can be seen on the screen to be of noticeably lower
> quality.
>
> In your reply you have explained more about this and told me how to
> predict dimensions and to accommodate dpi settings. But what about
> PRINTING?

As CSM1 indicated in another reply.. For printing, just print
at the same DPI you scanned the image at.

Scan a one inch wide document at 300 DPI, you get an image
that's 300 pixels across. Print the 300 pixels at 300 DPI
and you get a one inch wide image on paper. Print at
150 DPI and you get a 2 inch image. 600 DPI will give
you a 1/2 inch image.

The problem is if you view this 300 pixel image on your monitor
(that uses 85 pixels to make each inch) it will be 3.5 inches
wide. (300 pixels / 85 DPI = 3.5 inches).

Here's where the DPI setting of an image comes into play.
The DPI of an image has nothing to do with how big it looks
on a monitor and everything to do with how big it prints
on paper.

If you take your 300 pixel image and sample it down to
85 pixels, then it will appear one inch wide on a monitor
that uses 85 pixels to make an inch.

If you set the DPI of this image to 85, then it will print
at one inch. (Setting the image to 85 DPI is telling the
printer to spread 85 pixels across each inch of paper.
Since the image is 85 pixels across, then it will be one inch
wide. It has to be :) 

So.. Scan at a high resolution. Sample the resulting
image so the pixels match your monitor's resolution.
Then, change the DPI of the image file so the image prints
at the correct width/height.

Example:

By measuring the width of a monitor and dividing the
inches by the monitor's resolution, you get the
pixels per inch the monitor displays. Let's
say it calculates to 80 PPI.

You have a 6 inch wide document and you want it to be
6 inches wide on your monitor and you want it to be
6 inches wide when you print it.

Scan the document at 300 DPI. This will result in
a file that's 6 x 300 = 1800 pixels wide.

Sample the image to fit the screen. Since in this
example 80 pixels make up an inch of the screen,
you have to make the image 80 x 6 = 480 pixels
wide.

If you want this 480 pixel image to print on paper
at 6 inches, it has to be set to 80 DPI. Setting
it to 80 DPI tells the printer to spread 80 pixels
across each inch of paper. Since there are 480
pixels, the resulting print will be 6 inches wide.

The only downside to doing this is that you will
have a low resolution print. At 80 DPI, you lose
a lot of detail.

Unfortunatley, this is the only way you can have an
image appear the same size on your monitor AND on
your printer. If you want to print at high resolution,
then you'll have to scale the image on your monitor.

Here are a couple of web sites that explain the
same thing.. Perhaps a bit better :-)

http://www.scantips.com/

http://www.larry-bolch.com/dpi-revealed/

> So I figure that I should print the GIF at its "normal" size in order
> to avoid any noticeable reduction in quality. As my original post
> here mentions, I have tried to do this by (1) changing Twain settings
> as well as by (2) using resizing utilities. But I have had poor
> results. Maybe I am not using these applications correctly?
>
> As an alternative approach, perhaps there are image file formats
> which are better suited to resizing operations than GIF is?

Twain settings should have nothing to do with how the image looks.
What software are you using to size the images ?

Also.. If you don't need transparent backgrounds, there's no real
advantage to using GIF.. I'd use JPEG. The files use up less
disk space, and you have a lot more colors (This makes it better for
displaying photo images).

GIF can only display a maximum of 256 colors. For photos, this
results in a 'posterized' effect because color transitions aren't
smooth. JPEG images give you 16 million colors that result in
'photo quality' images.
Anonymous
February 9, 2005 5:33:17 PM

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

"Wayne Fulton" <nospam@invalid.com> wrote in message
news:4208126c$0$23561$8b463f8a@news.nationwide.net...
> In article <95F6E6B89D09271F3M4@130.133.1.4>, no_thanks@mail.com
> says...
> >
> >
> >How do I scan a map to a GIF so that when I view the GIF file at its
> >"normal" size it is a maginification of the original.
> >
> >In other words, what took one inch in the original document now takes
> >1.5 inches in the GIF at its normal size.
> >
> >----
> >
> >OTHER INFO ... I have tried to do this with my Epson Twain settings
> >but I seem to end up with a lower resolution (even though the
> >resoultion setting is kwpt the same).
> >
> >When I have a resizing utilities (like Pic2Pic) on a GIF file I seem
> >to get a quite noticeable drop in quality. Is this inherent in
> >resizing a GIF? Is it better to use a different image format such as
> >TIFF, PNG, JPG in order to enlarge the image after scanning?
>
>
>
> You said View, so I am assuming you want to view it on the video
> screen, instead of printing it. The best way (highest quality) to
> enlarge it on the video screen is to scan it again at 50% greater
> resolution. That will create 50% more pixels in each dimension, and so
> it will view on the screen at 50% larger size.
>
> Or you could resample an existing image to be 50% larger, but yes, that
> will loose quality. If you can scan it, then scan it.
>
> For the video screen, GIF is NOT the problem, GIF is desiged for the
> video screen. Certainly GIF is not the SIZE problem on the screen.
> GIF is limited to 256 colors, a problem for photographs, but this is
> surely no problem for a map. Probably you could even reduce it to 16
> colors for a smaller file without losing anything (but there are always
> some ifs and buts, I dont know what you have). Or you could use TIF or
> PNG, also very fine if you can use them. I would try hard NOT to use
> JPG for a map, quality suffers.
>
> The size problem might be because there are no inches in the video
> system, meaning that you cannot work in inches for the video screen.
> Your video screen is instead dimensioned in pixels, for example perhaps
> 1024x768 pixels is a common size.
>
> I dont know the size of your map, so I am making up numbers, but if for
> example, you scan a 6 inch paper map dimension at say 100 dpi, you will
> create 6x100 = 600 pixels of image dimension. This will fill 600
> pixels of your 1024 inch screen dimension. Regardless, more resolution
> is a larger image, less is smaller (on the video screen - printing
> works rather differently).
>
> Or per your question, if you instead scan this example at 150 dpi (50%
> more) it will create 900 pixels which will fill 900 pixels of your
> screen dimension, and it will appear 50% larger on the screen than the
> 100 dpi image.
>
> --
> Wayne
> http://www.scantips.com "A few scanning tips"
>
To add to Wayne's explanation, to print a document at the same size as the
original size, Print at the same DPI that you scanned it. To retain the DPI
in the saved image, you need to use TIFF, because GIF does not include the
DPI that the image was scanned at. JPEG saves the dpi, but does bad things
to map images.

If you scan at 300 DPI, Print the image at 300 DPI.
If you must use GIF, write a text file that tells what DPI you scanned at,
so that you know what DPI to print.

Or always scan at a fixed dpi and always print at that same dpi.

--
CSM1
http://www.carlmcmillan.com
--
February 9, 2005 7:00:12 PM

Archived from groups: comp.periphs.scanners,rec.photo.digital (More info?)

Franklin,

What you should be aware of and others have sort of mentioned but not
gone into, is that JPEG and GIF are popular compressed formats designed
to reduce file size. JPEG compresses pictures by eliminating detail
that is less important to your eye's impression of a complex continuous
tone image. It does a wonderful job of reducing file size of photos
while minimizing visual loss. But it is lossy in that information is
discarded. GIF is an older format designed for line art and logos. It
has a limited color pallet but once converted to 256 colors, compression
is lossless- all image detail is saved. GIF gives best results with
cartoons, maps, logos, text and the like, (large areas of single color
compress very efficiently) but does not give much compression where lots
of fine detail is present (pictures). It also can create posterization
artifacts in fine shadings due to the limited color depth. JPEG does
not do as well with line art as loss of fine detail and introduction of
edge artifacts become apparent as compression increases.

Thus your map may likely give a sharper, crisper, better image with good
compression as a GIF, while for a portrait on the web, JPEG would be far
superior. TIFF is totally lossless (good for archiving), not as
convenient in browsers, and may or may not be compressed. But
compression only relates to file size and does not directly have
anything to do with DPI.

This is all to explain that GIF vs JPG, TIFF or PNG is an issue of file
size, compression artifacts and software compatibility, but not the
answer to your image DPI resizing question.

I would suggest that you scan the map at 200-300 PPI for normal use and
maybe up to 600 PPI for enlargements. Then try the options in a good
(free) utility like IrfanView to resize, print and save as TIF or GIF.
Resample the image to different pixel dimensions and you will quickly
see the effect on default screen and print sizes.


CSM1 wrote:

> "Wayne Fulton" <nospam@invalid.com> wrote in message
> news:4208126c$0$23561$8b463f8a@news.nationwide.net...
>
>>In article <95F6E6B89D09271F3M4@130.133.1.4>, no_thanks@mail.com
>>says...
>>
>>>
>>>How do I scan a map to a GIF so that when I view the GIF file at its
>>>"normal" size it is a maginification of the original.
>>>
>>>In other words, what took one inch in the original document now takes
>>>1.5 inches in the GIF at its normal size.
>>>
>>>----
>>>
>>>OTHER INFO ... I have tried to do this with my Epson Twain settings
>>>but I seem to end up with a lower resolution (even though the
>>>resoultion setting is kwpt the same).
>>>
>>>When I have a resizing utilities (like Pic2Pic) on a GIF file I seem
>>>to get a quite noticeable drop in quality. Is this inherent in
>>>resizing a GIF? Is it better to use a different image format such as
>>>TIFF, PNG, JPG in order to enlarge the image after scanning?
>>
>>
>>
>>You said View, so I am assuming you want to view it on the video
>>screen, instead of printing it. The best way (highest quality) to
>>enlarge it on the video screen is to scan it again at 50% greater
>>resolution. That will create 50% more pixels in each dimension, and so
>>it will view on the screen at 50% larger size.
>>
>>Or you could resample an existing image to be 50% larger, but yes, that
>>will loose quality. If you can scan it, then scan it.
>>
>>For the video screen, GIF is NOT the problem, GIF is desiged for the
>>video screen. Certainly GIF is not the SIZE problem on the screen.
>>GIF is limited to 256 colors, a problem for photographs, but this is
>>surely no problem for a map. Probably you could even reduce it to 16
>>colors for a smaller file without losing anything (but there are always
>>some ifs and buts, I dont know what you have). Or you could use TIF or
>>PNG, also very fine if you can use them. I would try hard NOT to use
>>JPG for a map, quality suffers.
>>
>>The size problem might be because there are no inches in the video
>>system, meaning that you cannot work in inches for the video screen.
>>Your video screen is instead dimensioned in pixels, for example perhaps
>>1024x768 pixels is a common size.
>>
>>I dont know the size of your map, so I am making up numbers, but if for
>>example, you scan a 6 inch paper map dimension at say 100 dpi, you will
>>create 6x100 = 600 pixels of image dimension. This will fill 600
>>pixels of your 1024 inch screen dimension. Regardless, more resolution
>>is a larger image, less is smaller (on the video screen - printing
>>works rather differently).
>>
>>Or per your question, if you instead scan this example at 150 dpi (50%
>>more) it will create 900 pixels which will fill 900 pixels of your
>>screen dimension, and it will appear 50% larger on the screen than the
>>100 dpi image.
>>
>>--
>>Wayne
>>http://www.scantips.com "A few scanning tips"
>>
>
> To add to Wayne's explanation, to print a document at the same size as the
> original size, Print at the same DPI that you scanned it. To retain the DPI
> in the saved image, you need to use TIFF, because GIF does not include the
> DPI that the image was scanned at. JPEG saves the dpi, but does bad things
> to map images.
>
> If you scan at 300 DPI, Print the image at 300 DPI.
> If you must use GIF, write a text file that tells what DPI you scanned at,
> so that you know what DPI to print.
>
> Or always scan at a fixed dpi and always print at that same dpi.
>
!