Are .gif files limited to 72 dpi?
Peter Kronenberg
Everytime I save a file in .gif format, when I reload it and look at
the Image Information, it says that the resolution is 72 pixels per
inch, even though I never changed the resolution.
Peter
Beth Winter
IIRC GIF doesn't store the resolution information, so the default is
used. You can set this default under File > Preferences > General >
Rulers & Units
--
Beth Winter, PSP terrorist - New Millenium Division
The Discworld Compendium <http://www.extenuation.net/disc/>
"To absent friends, lost loves, old gods and the season of mists."
-- Neil Gaiman
Kris Zaklika
I don't think the GIF format saves a resolution setting.
This setting is only any use for determining the size of
the image when it is printed. The resolution of a GIF
image you open is determined by the default resolution
found in File > Preferences > General Program Preferences
under the Rulers and Units tab. You can set the resolution
of any individual image by doing Image > Resize and clicking
the Actual/print size section. Type the new resolution
value in the Resolution box but do _not_ type anywhere
else or change _any_ other setting. Then press OK.
--
----------------------------------------------------------------------
Kris Zaklika Jasc Software, Inc. The
Product Ideas: id...@jasc.com Power
Customer Service: customer...@jasc.com To
Technical Support: tec...@jasc.com Create
----------------------------------------------------------------------
Peter Kronenberg
>Peter Kronenberg wrote:
>>
>> Are .gif files limited to a resolution of 72 pixels per inch?
>> Everytime I save a file in .gif format, when I reload it and look at
>> the Image Information, it says that the resolution is 72 pixels per
>> inch, even though I never changed the resolution.
>
>IIRC GIF doesn't store the resolution information, so the default is
>used. You can set this default under File > Preferences > General >
>Rulers & Units
>
>--
>Beth Winter, PSP terrorist - New Millenium Division
I thought the default resolution was for new images. Can't PSP
figure out the resolution of an existing file? If I have a file at
300 dpi and save it as a .gif, when I open it up again and it displays
as 72 dpi, have I lost resolution?
Peter
Peter Kronenberg
>Peter Kronenberg wrote:
>>
>> Are .gif files limited to a resolution of 72 pixels per inch?
>> Everytime I save a file in .gif format, when I reload it and look at
>> the Image Information, it says that the resolution is 72 pixels per
>> inch, even though I never changed the resolution.
>> Peter
>
>I don't think the GIF format saves a resolution setting.
>This setting is only any use for determining the size of
>the image when it is printed. The resolution of a GIF
>image you open is determined by the default resolution
>found in File > Preferences > General Program Preferences
>under the Rulers and Units tab. You can set the resolution
>of any individual image by doing Image > Resize and clicking
>the Actual/print size section. Type the new resolution
>value in the Resolution box but do _not_ type anywhere
>else or change _any_ other setting. Then press OK.
>
Thanks. I'm familiar with how to change the resolution; I'm just
confused about how it applies to gif files.
Does changing the resolution of a gif file actually make any changes
to the file?
Peter
Kris Zaklika
>
> Beth Winter <ren...@astercity.net> wrotd:
>
> >Peter Kronenberg wrote:
> >>
> >> Are .gif files limited to a resolution of 72 pixels per inch?
> >> Everytime I save a file in .gif format, when I reload it and look at
> >> the Image Information, it says that the resolution is 72 pixels per
> >> inch, even though I never changed the resolution.
> >
> >IIRC GIF doesn't store the resolution information, so the default is
> >used. You can set this default under File > Preferences > General >
> >Rulers & Units
> >
> >--
> >Beth Winter, PSP terrorist - New Millenium Division
>
> I thought the default resolution was for new images.
The resolution setting I mentioned is the resolution for
new images and for image formats that do not store a
resolution value in the image file. GIF represents the
latter case.
> Can't PSP
> figure out the resolution of an existing file?
Let me give you an analogy. I write my address down on a
piece of paper. Before I hand it to you I tear off the
house number, leaving just the street. Can you figure out
the number of my house looking only at the piece of paper
in your hand? This is what happens when you save a GIF
file - the current resolution value is thrown away.
> If I have a file at
> 300 dpi and save it as a .gif, when I open it up again and it displays
> as 72 dpi, have I lost resolution?
What do you mean by "lost resolution"? You have not, repeat
not, lost any image information. Image information is carried
by pixels. As long as you have the same number of pixels
before and after saving (which you do) no damage to the
image occurs and there is no loss of information. All that
the resolution number means is how many image pixels will
correspond to one inch of width or eight on paper when the
image is printed. You have lost this number by saving as
GIF - that's all. You can change the resolution at will
from 0.01 to 2540 pixels per inch (and keep doing it) with
absolutely no effect on the information in the image. The
only time resolution is of any importance is when you
print an image. Then, a value of 200 pixels per inch will
get you about all of the quality of which your printer is
capable. Anything above 300 pixels per inch is a waste of
time. If I were you I'd be more worried about working with
images that have no more than 256 colors (all that GIF
allows) instead of the normal 16.7 million colors.
> Peter
Kris Zaklika
See my other post. Since the resolution number is not stored
in the GIF file format, whatever you have currently set just
gets thrown away. It is never stored in the file so it does
not change the file. If you mean, does throwing away the
resolution change the image, then it does not in any way at
all.
> Peter
Ronald Vick
Kronenberg) wrote:
No. You seem to think that the printer resolution has something to do
with the image you see. It doesn't. All the DPI setting does is to
tell the printer how many dots per inch to print. It's not used
anywhere else.
Your image always stays the same, no matter how large or small you
print it on the printer by changing the DPI setting. (and even then,
there are many ways to over-ride the DPI setting, such as printing to
the full paper size or using the manual adjust to vary the image size
on paper.
Since GIF wasn't originally designed to store this setting by it's
creators (Compuserve), PSP just defaults to the 72 DPI printer
setting.
Ron
Peter Kronenberg
another application, for example, Microsoft Word, and it will
ultimately be printed.
I scan my picture at 300 dpi, save it as a PSP file and do any editing
I need to do. Now, when I save it as a GIF (let's say that's the only
format supported by the application), I open it later and it says 72
DPI. So I'll still get the full resolution when I print it from
another application?
I thought that when you use PSP to increase the resolution of an
image, it actually adds pixels by averaging adjacent pixels or
something like that.
Ronald Vick <Ron...@cfl.rr.corn> wrotd:
Peter
Kris Zaklika
>
> So let's say that I'm saving a GIF file that will be imported by
> another application, for example, Microsoft Word, and it will
> ultimately be printed.
> I scan my picture at 300 dpi, save it as a PSP file and do any editing
> I need to do. Now, when I save it as a GIF (let's say that's the only
> format supported by the application), I open it later and it says 72
> DPI. So I'll still get the full resolution when I print it from
> another application?
I'm afraid that is up to the other application. It decides
how it scales an image for printing, not PSP. However, every
pixel in the image is given to the application for its use.
It can use it properly or not - that's not up to PSP. I'm
not sure why you use GIF for this task. Many applications
support the PCX format - even ancient ones - because it is
what was used by old versions of MS Paint (the ones made by
ZSoft). A PCX image may be more convenient for you. This is
because it can support 24-bit color images (with lossless
compression) or palettized images like those in GIF. For
both type of images it saves the resolution setting.
--
Ilya Razmanov
"Peter Kronenberg" <pak@nospam_carouselpuppets.com> wrote in message
news:3cac5528....@news.nova.org...
> So let's say that I'm saving a GIF file that will be imported by
> another application, for example, Microsoft Word, and it will
> ultimately be printed.
> I scan my picture at 300 dpi, save it as a PSP file and do any editing
> I need to do. Now, when I save it as a GIF (let's say that's the only
> format supported by the application), I open it later and it says 72
> DPI. So I'll still get the full resolution when I print it from
> another application?
You get all pixels saved from PSP (that is, all pixels present at the image
right before you save it. PSP do not cut pixels on saving) and resolution
assigned by the application you import to. That is, you get all pixels but
"meters" or "inches" depends only on that other application.
> I thought that when you use PSP to increase the resolution of an
> image, it actually adds pixels by averaging adjacent pixels or
> something like that.
Yes (however there's more than one option to add pixels) but it has
absolutely nothing to do with "how large that unknown application will print
your image". Every pixel present at your image right before save will be
transferred to that other application. How will it deal with them - depends
solely on that application.
Be warned, however, that GIFs cannot have more than 256 colors so it's not
the good file format choice.
Ilyich.
--------------------------------------------------------------------------
Ilya Razmanov (a.k.a. Ilyich the Toad)
http://photoshop.msk.ru/ - Photoshop plug-in filters
"Stop him, Sam, he's gonna tell us a story!" - Max,
Sam and Max hit the road
--------------------------------------------------------------------------
Peter Kronenberg
The anwer to that is easy --- ignorance on my part :-)
There are so many formats, I can't keep up. I basically use JPG for
photographs and GIFs for simple pictures like logos and line art.
That way, I don't have too many rules to keep track of. But I'm
willing to learn.
> Many applications
>support the PCX format - even ancient ones - because it is
>what was used by old versions of MS Paint (the ones made by
>ZSoft). A PCX image may be more convenient for you. This is
>because it can support 24-bit color images (with lossless
>compression) or palettized images like those in GIF. For
>both type of images it saves the resolution setting.
Peter
Kris Zaklika
>
> .> I'm not sure why you use GIF for this task.
>
> The anwer to that is easy --- ignorance on my part :-)
> There are so many formats, I can't keep up. I basically use JPG for
> photographs and GIFs for simple pictures like logos and line art.
> That way, I don't have too many rules to keep track of. But I'm
> willing to learn.
That's why we're here - to help out with things like this.
And it's always good to encounter a person willing to learn.
None of us was born with all the knowledge we have now. Be
cautious about using JPEG for photos if you are going to
manipulate or adjust your images and save repeatedly. The
repeated lossy compression will lead to quality degradation
of your image. Better to work in something like the PSP
format until you know you have the final image you need.
> > Many applications
> >support the PCX format - even ancient ones - because it is
> >what was used by old versions of MS Paint (the ones made by
> >ZSoft). A PCX image may be more convenient for you. This is
> >because it can support 24-bit color images (with lossless
> >compression) or palettized images like those in GIF. For
> >both type of images it saves the resolution setting.
>
> Peter
--
Ilya Razmanov
"Kris Zaklika" <kzak...@jasc.com> wrote in message
news:3CAC5F98...@jasc.com...
> Peter Kronenberg wrote:
> >
> > .> I'm not sure why you use GIF for this task.
> >
> > The anwer to that is easy --- ignorance on my part :-)
> > There are so many formats, I can't keep up. I basically use JPG for
> > photographs and GIFs for simple pictures like logos and line art.
> > That way, I don't have too many rules to keep track of. But I'm
> > willing to learn.
>
> That's why we're here - to help out with things like this.
> And it's always good to encounter a person willing to learn.
How true...
> None of us was born with all the knowledge we have now. Be
> cautious about using JPEG for photos if you are going to
> manipulate or adjust your images and save repeatedly. The
> repeated lossy compression will lead to quality degradation
> of your image. Better to work in something like the PSP
> format until you know you have the final image you need.
Dropping in my two cents, I'd also not recommend JPEGs for printing. The
thing which is white in original may have slight (invisible on screen) color
shift after JPEG compression and, as a result, produce silly sparse halftone
dots in print right there you don't want them. IMHO JPEG always gives most
noticeable losses right in the areas that are difficult to print (very light
and light, yet saturated) and the areas where print gives more shades than
screen (very dark and saturated).
Ilyich.
--------------------------------------------------------------------------
Ilya Razmanov (a.k.a. Ilyich the Toad)
http://photoshop.msk.ru/ - Photoshop plug-in filters
"Sam: Brutal.
Max: But very true to life" - Sam and Max hit the road
--------------------------------------------------------------------------
Ronald Vick
wrote:
>So let's say that I'm saving a GIF file that will be imported by
>another application, for example, Microsoft Word, and it will
>ultimately be printed.
>I scan my picture at 300 dpi, save it as a PSP file and do any editing
>I need to do. Now, when I save it as a GIF (let's say that's the only
>format supported by the application), I open it later and it says 72
>DPI. So I'll still get the full resolution when I print it from
>another application?
>I thought that when you use PSP to increase the resolution of an
>image, it actually adds pixels by averaging adjacent pixels or
>something like that.
Let's take that in reverse order...
>I thought that when you use PSP to increase the resolution of an
>image, it actually adds pixels by averaging adjacent pixels or
>something like that.
No! No! A thousand times No! You're confusing size of an image with
the printer resolution. No matter what you change the DPI setting
to, the actual image never changes.
Maybe it would help to walk you though the actual process.
You scan an image at 300 DPI. Now, how big is the image? The rate
setting of the scanner doesn't tell us. We need to know how big the
scanned area was. Let's say that we scanned a 3 x 3 inch image,
giving us an image of 900 x 900 pixels.
Now, if we have a monitor with a display set to 1024 x 768 pixels,
it's obvious that the image will be larger in height than the display
and slightly smaller in width than the monitor.
Now, we plug in a DPI setting of 150. Since this is just a value
saved for use by the printer, nothing happens to the monitor display.
In fact, we can change the DPI setting to any value that can be loaded
into the setting and the monitor display (and size of the image) will
not change.
Why should it? The image isn't changed by the printer settings. The
image size remains 900 x 900 pixels.
However, if we print the image, the printer driver software looks at
the DPI setting to determine the width and height of the printed
image. The printer driver takes the total pixels, divides by the DPI
setting and for the values above, prints a 6 x 6 inch image. (900
pixels divided by 150 dpi = 6 inches)
If we change the DPI setting to 450 DPI, the printed image becomes a 2
x 2 inch picture. (900 pixels divided by 450 dpi = 2 inches)
In the two previous examples, the image size of 900 x 900 pixels
stayed the same in the computer and on screen, and only the printed
image changed.
Note that if the printer cannot print at this resolution, It ignores
whatever pixels it cannot print. (you cannot trust printer
specifications as to DPI values, since they only list the maximum
number of dots that can be printed. In order to print different
colors at different lightness levels, the actual maximum Value is
usually about one tenth the sales rating.) People bragging about a
1600 dpi printer might be surprised to find out that they can only
print out a 160 line per inch image in color. This is the real
resolution of the printer, and has little to do with the image we're
working with.
Now, you save the image in GIF format. It's saved as a 900 x 900
pixel image, and the printer DPI setting is ignored.
When you load it into another program, that program will load it as a
900 x 900 pixel image. Whatever printer resolution that program uses
is set by the program, all we know for certain at this point is that
the actual size of the image is 900 x 900 pixels.
Word for Windows, for example, tries to load images at the maximum
size allowed by the paper width settings, and allows you to resize on
the fly with a crude selection resize. DPI settings that are
available in formats other than GIF are ignored.
Ron
Ilya Razmanov
"Ronald Vick" <Ron...@cfl.rr.corn> wrote in message
news:3qnpaug9pq8gegfm5...@4ax.com...
> On 04 Apr 2002 13:33:07 GMT, in comp.graphics.apps.paint-shop-pro you
> wrote:
>
>
> >I thought that when you use PSP to increase the resolution of an
> >image, it actually adds pixels by averaging adjacent pixels or
> >something like that.
>
>
> No! No! A thousand times No! You're confusing size of an image with
> the printer resolution. No matter what you change the DPI setting
> to, the actual image never changes.
>
Hm. A second time during these days we are talking about one thing from two
different points ;-) Guess I'd better be more clear about "just changing a
DPI" and "changing a pixel size" next time. I always forget that there are
dozens ways to misunderstand it ;-))) It may only be compared to the number
of ways people confuse "greyscale" vs "black and white" and "ppi" vs "dpi"
;-)
Ok, let's read that "Resampling vs Resizing" thread closely...
Ilyich.
--------------------------------------------------------------------------
Ilya Razmanov (a.k.a. Ilyich the Toad)
http://photoshop.msk.ru/ - Photoshop plug-in filters
"Never pay more then 20 bucks for a computer game" - Guybrush Threepwood,
Monkey Island
--------------------------------------------------------------------------
Ronald Vick
<ily...@cacr.ioc.ac.ru> wrote:
>
>"Ronald Vick" <Ron...@cfl.rr.corn> wrote in message
>news:3qnpaug9pq8gegfm5...@4ax.com...
>> On 04 Apr 2002 13:33:07 GMT, in comp.graphics.apps.paint-shop-pro you
>> wrote:
>>
>>
>> >I thought that when you use PSP to increase the resolution of an
>> >image, it actually adds pixels by averaging adjacent pixels or
>> >something like that.
>>
>>
>> No! No! A thousand times No! You're confusing size of an image with
>> the printer resolution. No matter what you change the DPI setting
>> to, the actual image never changes.
>>
>
>Hm. A second time during these days we are talking about one thing from two
>different points ;-) Guess I'd better be more clear about "just changing a
>DPI" and "changing a pixel size" next time. I always forget that there are
>dozens ways to misunderstand it ;-))) It may only be compared to the number
>of ways people confuse "greyscale" vs "black and white" and "ppi" vs "dpi"
>;-)
>
>Ok, let's read that "Resampling vs Resizing" thread closely...
>
>Ilyich.
Peter was confusing image size with printer resolution. I was trying
to get him on track.
It actually appears that we said the same thing to him, but from
different viewpoints, both of which are correct.
I've never understood why people want to mistake a rate for a size.
It's almost as if they want to describe the distance between two
cities by the speed limit. ie: "How far is it from city A to city B?"
Ans: "65 miles per hour!" which may be good to know, but it doesn't
answer the question.
I had a girlfriend once that just could not grasp the idea of speed.
She tried to tell a traffic policeman that she couldn't have been
traveling at 60 mph in a 35 mph speed zone because she hadn't driven
the car over a mile when she was caught.
She never did understand why she was ticketed and fined for speeding.
According to her logic, the car had to have moved over a mile before
you could have a speed. "That's why there's a 'Miles' in MPH!"
I really must re-establish contact with her, just to see if she
managed to keep her driver's license.
True story!
Ron
Ilya Razmanov
"Ronald Vick" <Ron...@cfl.rr.corn> wrote in message
Yes, precisely. But, since I tend to think of size "in pixels" (maybe
because of that I know how easy it is to reset the resolution and how
difficult is to calculate pixels. Or maybe just because I've spent much time
on plugins where everything is in pixels), I always tend to understand
"resizing" as "resampling" and reply that way. I'm afraid this thread is not
the only one I've made this mistake. I should remember this point of
confusion better, otherwise, for example, our answers, being both correct,
may sound as "contradictory" and raise even more confusion ;-)
> I've never understood why people want to mistake a rate for a size.
> It's almost as if they want to describe the distance between two
> cities by the speed limit. ie: "How far is it from city A to city B?"
> Ans: "65 miles per hour!" which may be good to know, but it doesn't
> answer the question.
You know, it seems that this sort of question is quite popular in Fireworks
and Photoshop groups as well. In the former, it is known as "why do my
prints look blurry?", in the latter as "what resolution to be set for Web?"
The funniest one I ever answered in PS NG was "how do I make my Web images
to be shown in print size?" The funniest thing was that, after I explained
why it can't be done, original poster called my answer OT because he was not
interested to know "why", he wished to know "how" ;-)))
> I had a girlfriend once that just could not grasp the idea of speed.
> She tried to tell a traffic policeman that she couldn't have been
> traveling at 60 mph in a 35 mph speed zone because she hadn't driven
> the car over a mile when she was caught.
Interesting. If I were her, I'd answer that I hadn't driven the car over an
hour when I was caught. However, if I were her, I'd be good lookin' ;-)
Ilyich.
--------------------------------------------------------------------------
Ilya Razmanov (a.k.a. Ilyich the Toad)
http://photoshop.msk.ru/ - Photoshop plug-in filters
"What did these humans design this for, anyway?"
- Bender, Futurama
--------------------------------------------------------------------------
kirki...@gmail.com
This applies to the OP's question. I can open the new file at 150 but the only way to save it is Save for Web and which applies a ppi of 72. People keep saying it doesnt matter but they're asking for 150.