On Saturday 23 April 2011 07:53:49 Carusoswi wrote:

So, I have used Gimp to downsize large architectural drawing

images from

Tiff's to jpgs. Well, I always thought I was downsizing them. In

the

past, the process always seemed to make the files more usable

in the

application where I need to use the architectural drawings

without a

significant loss in quality.

This morning, I have had trouble following 'my process'.

Typically, I will

open a tiff in Gimp, save as jpg, export if prompted, then select

quality

of 40 or 50 percent, and the result is a usable file that is

significantly

smaller than the source tiff file.

Today, the source tiff which is 900 mb in size is being converted

to jpg

which is 6 or 7 mb in size, totally unusable.

Additionally, if I simply open the source in Gimp, save it to

another

directory from Gimp without making any changes, the file also

grows to 6

or 7 mb.

What am I doing wrong this morning that I have not been doing

wrong for the

last 6 months?

I am stumped (and frustrated because I have work to do).

Using version 2.6.11 in Ubuntu 10.10 if that matters.

I have a version of 2.7 on my Windows XP OS, and it will lock up

trying to

open these drawings.

It's curious, because, at 900 MB, I typically can use the drawings

without

even altering or downsizing them. Today, it's a problem.

What I really cannot understand is why Gimp is causing

unaltered files to

grow in size when saving them. Is that normal?

Advice will be most appreciated.

Caruso

Are the architectural drawings available in a vector format such as svg or pdf? These are normally much smaller for drawings etc. than their bitmapped equivalents.

If not you might have better luck importing them as bitmaps into Inkscape and then converting them to svg or pdf using either trace mode or outline mode.

Carusoswi gimpusers.com> writes:

So, I have used Gimp to downsize large architectural drawing images from

Tiff's to jpgs.

Let's be precise. You are not "downsizing" the images. "Downsize" means making a picture physically smaller, as in, having less pixels. According to your own description, you are not doing this. What you are doing is saving the file in another format which has better compression.

Today, the source tiff which is 900 mb in size is being converted to jpg which is 6 or 7 mb in size, totally unusable. Additionally, if I simply open the source in Gimp, save it to another directory from Gimp without making any changes, the file also grows to 6 or 7 mb.

Now I'm completely confused. You say the original is 900MB. then you say it "grows" to 6-7MB. But 900 is much larger than 6 or 7! Please explain. Did you by any chance mean 900KB and not MB? that would explain it.

What I really cannot understand is why Gimp is causing unaltered files to grow in size when saving them. Is that normal?

The TIFF format has many options, including several compression modes, and also an uncompressed mode. So, assuming you meant 900KB: You probably opened a compressed TIFF, and then when you saved the file, GIMP saved it as an uncompressed one. If the file has a lot of empty space - as in, a large empty area of white (or other) color - it will compress dramatically. When you re-save the TIFF, a dialog should open after you set the file name and folder. Choose "LZW" instead of "none" and see if that solves the TIFF re-saving issue.

Also, because of the differences in compression types, some images that compress very well in TIFF's type of compression, compress very badly in JPG-type compression. The type of images that do this are images which have lots of very thin lines, in other words: blueprints. I don't have a good solution for saving this type of file in JPG. It really depends on why you want to re-save the file to JPG in the first place.

So, I have used Gimp to downsize large architectural drawing images from Tiff's to jpgs. Well, I always thought I was downsizing them. In the past, the process always seemed to make the files more usable in the application where I need to use the architectural drawings without a significant loss in quality.

This morning, I have had trouble following 'my process'. Typically, I will open a tiff in Gimp, save as jpg, export if prompted, then select quality of 40 or 50 percent, and the result is a usable file that is significantly smaller than the source tiff file.

Today, the source tiff which is 900 mb in size is being converted to jpg which is 6 or 7 mb in size, totally unusable.

Additionally, if I simply open the source in Gimp, save it to another directory from Gimp without making any changes, the file also grows to 6 or 7 mb.

What am I doing wrong this morning that I have not been doing wrong for the last 6 months?

I am stumped (and frustrated because I have work to do).

Using version 2.6.11 in Ubuntu 10.10 if that matters.

I have a version of 2.7 on my Windows XP OS, and it will lock up trying to open these drawings.

It's curious, because, at 900 MB, I typically can use the drawings without even altering or downsizing them. Today, it's a problem.

What I really cannot understand is why Gimp is causing unaltered files to grow in size when saving them. Is that normal?

Hi,

There are tiffs and tiffs, see http://en.wikipedia.org/wiki/Tagged_Image_File_Format, however what happens if you save to png first, rather than as a tiff as defined by gimp (where some compression may have been removed).

If you save to png, I would be interested in the resulting size, and then if you convert to jpg from that, what size is the jpg.

Owen

> Also, because of the differences in compression types, some images that > compress very well in TIFF's type of compression, compress very badly in > JPG-type compression. The type of images that do this are images which have
> lots of very thin lines, in other words: blueprints. I don't have a good > solution for saving this type of file in JPG. It really depends on why you
> want to re-save the file to JPG in the first place.

I would like to add that JPG is supposed to be used with photographs. It's one of the least suitable formats you could use for drawings. Unnecessary big file size with unnecessary low quality. I really wonder how you could work with a quality of 40-50. You should have suffered from very bad artefacts...

The best format would be a vector graphic as suggested. But from my experience it's hard to get a good one from pixel files. It might look good at one spot but on another some stuff is missing which you won't recognize from the beginning.
My suggestion is to either use TIFF with compression (was already suggested) or to use PNG (or even GIF). The latter ones where designed to fit drawings. PNG is even lossless. GIF is somewhat obsolete but you might try it anyway.

Typical compression rates in the files I use: uncompressed TIFF with 2-3 MB, PNG with 200-300 KB.

Regards, Mathias

Mathias Lindner wrote:

The best format would be a vector graphic as suggested. But from my experience it's hard to get a good one from pixel files.

There are programs you can use that can convert (or try to convert) a bitmap image to a vector graphic one. One such option is Autotrace which you can get from SourceForge at http://autotrace.sourceforge.net/.

On Sunday, April 24, 2011 02:23:41 pm Carusoswi wrote:

Mathias Lindner wrote:

The best format would be a vector graphic as suggested.

But from my

experience it's hard to get a good one from pixel files.

There are programs you can use that can convert (or try to

convert) a

bitmap image to a vector graphic one. One such option is

Autotrace which

you can get from SourceForge at

http://autotrace.sourceforge.net/.

Thanks for all the replies. It might make my situation clearer if

I

explain that I do not need to maintain much quality when

converting these

drawings, except that I need to preserve s certain level of detail

so that

I can read them after I import them into the application for

which I am

trying to downsize.

Of course, the problem that I have run into this morning was

that my

application was choking on the tiff files, and most of the

solutions I

tried either did not result in smaller files, or the smaller result

was so

fuzzy that I could not make out certain details I need in order to

work

with the drawings.

I did manage to crop away unnecessary areas of the original

tiffs, so was

finally able to import them at their full resolution into my

application

so that I could complete my project.

Will try all the mentioned solutions to see which yields the

optimum

results. I'm not certain my application can work with gif's,

however.

Thanks again.

Caruso

Gifs are only suitable for web pages. So that should not be an issue one would hope.

With respect to your original tiff files, if you have a suitable viewer you can view them as is. On Slackware Linux I have several, including XV and Gwenview. Ubuntu typically doesn't come with a complete set of tools but you could try downloading either of the two I mention above. Then once set at a suitable enlargement you can use Ksnapshot to save the drawing as a png file at 72dpi.