I have an 8-page document. Each page has one large photo and a text heading. Is there a way to export to pdf so that some of the pages compress their images while other pages do not? Three of the photos are low res (72 dpi) and do not look good with compression.
If not, I thought I might resample them up from within CorelDraw so they are comparable to the res of the photos on the other pages (~200dpi) and compress to around 85% jpg.
As far as I know Janet if you set you bitmap downsampling to a minimum number that you want, anything under that resolution will stay as it is.
In the screen cap anything over 200PPI will be reduced to 200 leaving anything under 200 untouched.
Chris said:mmm... 16bit Tifs on my system are approx half the size when you LZW compress them.
That's interesting! A lot of articles on internet said LZW compression on 16-bit TIFFs creates a LARGER file...??? Usually they gave test comparisons, and the LZW was always much bigger. Do you have any ideas why your 'technique' of LZW settings are so successful compared to others....:-)....?
Janet Berg said:A lot of articles on internet said LZW compression on 16-bit TIFFs creates a LARGER file...???
it's "larger" if you compare it with JPG file compression, but it's enough for most jobs
Ariel---I found it. The article also explains why the difference between the different photos. But what is important here is the comparison of the different compression results for a given picture. The article can be seen at http://havecamerawilltravel.com/photographer/tiff-image-compression-lzw-zip . All such comparisons (on different sites) seem to give a larger file when using LWZ.
Anxious to hear from Chris how he gets his to reduce so much....:-)....
OK. I think I need a major re-evaluation here.....
Most of my photos are slightly smaller than A4, which is the doc size. One almost-full-page picture per page. They are usually ~200 dpi, and ~1000+ x ~1000+ pixels and all are 24-bit. They are photos of jewelry: reflective surfaces with dramatic lighting. They won't look shiny and sparkly if not really sharp. I find that reduction to jpgs are often not acceptable when making up a PDF brochure to send to clients. Using either zip or LZW would still leaves files way too big. So I thought jpg was my only viable option for considerably reducing file size. So given what you say, I will now check out reducing the bit size. I always just assumed that would screw up the picture. I will see if I can find something on the net that shows the same pic in different bits, if not, I will test it out myself.....
PS All my posts were about 16-bit and higher.
Reducing bit depth sounds like a very dangerous way to get smaller files, and I assume there is some kind of misunderstanding when you mention 16-bit files. When talking about 16-bit TIFFs they mean 16 bits per channel, while a normal RGB "only" has 8 bits per channel, R, G and B (8 x 3 = 24 bits in total). Reducing a 24-bit image to 16 bits (total) the number of possible colors will be reduced drastically, from 16,777,216 to only 4,096. Is there any special reason you can not work with the original images and use LZW or ZIP compression? FWIW, a 48 bit TIFF (16 bits per channel) can have 281 trillion possible colors!
Hi Ronny!
Ronny Axelsson said: Reducing bit depth sounds like a very dangerous way to get smaller files, and I assume there is some kind of misunderstanding when you mention 16-bit files. When talking about 16-bit TIFFs they mean 16 bits per channel, while a normal RGB "only" has 8 bits per channel, R, G and B (8 x 3 = 24 bits in total). Reducing a 24-bit image to 16 bits (total) the number of possible colors will be reduced drastically, from 16,777,216 to only 4,096.
Reducing bit depth sounds like a very dangerous way to get smaller files, and I assume there is some kind of misunderstanding when you mention 16-bit files. When talking about 16-bit TIFFs they mean 16 bits per channel, while a normal RGB "only" has 8 bits per channel, R, G and B (8 x 3 = 24 bits in total). Reducing a 24-bit image to 16 bits (total) the number of possible colors will be reduced drastically, from 16,777,216 to only 4,096.
Yes, I never would have even considered it before this thread.
A tiff that has 16 bits per channel, I call "a 16-bit tiff". Since a tiff is a file, it would then be "a 16-bit file"....:-)....
Ronny Axelsson said: Is there any special reason you can not work with the original images and use LZW or ZIP compression?
Is there any special reason you can not work with the original images and use LZW or ZIP compression?
Janet Berg said:A tiff that has 16 bits per channel, I call "a 16-bit tiff". Since a tiff is a file, it would then be "a 16-bit file"
Janet Berg said:As posted earlier, file sizes too large.
Janet Berg said:The original question was if you could make a multiple page pdf file in CorelDraw that compressed image files on some of the pages but did not compress them on others in order to avoid compression of images of low resolution.
Ronny Axelsson said: Janet Berg The original question was if you could make a multiple page pdf file in CorelDraw that compressed image files on some of the pages but did not compress them on others in order to avoid compression of images of low resolution. No. If you want to export as one single PDF, all pages will be treated the same way.Use lossless compression and it doesn't make any difference whether the image is high or low resolution.
Janet Berg
No. If you want to export as one single PDF, all pages will be treated the same way.Use lossless compression and it doesn't make any difference whether the image is high or low resolution.
So we've come around full circle here.... :-).... The lossless compressions don't adequately reduce the file size......