Zhang Weiwu on wrote...
| Anthony Thyssen дµÀ:
| > Zhang Weiwu on wrote...
| > | Dear list:
| > |
| > | This is my first time try convert(1). I did this:
| > | $ convert 1329.jpg 1330.jpg -adjoin identity.tiff
| > |
| > | The two images are here:
| > | gopher://sdf.lonestar.org/I/users/weiwu/1329.jpg
| > | gopher://sdf.lonestar.org/I/users/weiwu/1330.jpg
| > |
| > | Both images are less then 300KB in size, however the converted tiff
| > | image is as big as 1331KB. This is strange as tiff file is twice as big
| > | as it should be. As compression method shouldn't been changed (still
| > | JPEG inside the TIFF) I wonder how this comes to be and, is there a way
| > | to generate tiff image less then 600KB? Thanks in advance!
| > |
| > | I also tested the generated tiff image to make sure it's still in JPEG
| > | compression:
| > |
| Well, my understanding is, that since re-saving is a lossy operation,
| convert(1) should try to avoid such operation, then the default value
| should be when doing converting, do not try to re-compress, e.g. only
| encapsulate the jpeg with TIFF format but not to touch the raw image
| data. I am not sure if this is possible but if it's possible, there
| should be an option letting convert(1) acting this way or this should be
| default behavior of convert(1). How do you think?
This is what the 'delegate' conversion system is about. But it does this
by avoiding reading in images.
However IM is by its nature a Image Manipulation Package. That means
for most situations it just decodes from a large number of formats,
modifies the image, then writes it to one of a large number of formats.
It would be imposible for it to know how to convert from one format
directly to another, for ALL those formats. With more than 100 formats
known, that means 10,000 different methods must be needed.
It is thus NOT POSIBLE for a general image converter to handle what you
ask without decoding the lossy JPEG format.
Someone would have needed to write something specific for TIFF to do
this.
I suggest you just don't save as JPEG compression in the TIFF format,
or try to find a program that can do it without loss. It is not likely.
If you do find such a program. Great, let me know too, so I can add a
note about it in IM Examples, for the TIFF format...
http://www.imagemagick.org/Usage/formats/#tiff
Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]>
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