Anthony Thyssen 写道:
> 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:
> |
> Did you try adjusting the -quality setting for the JPEG's?
>
> Does that make a difference?
>
> Also reading and re-saving JPEG files (with JPEG lossy compression)
> is NOT a good idea. Doing so degrades the image. That is the price you
> pay for using a higly compressed JPEG image.
>
> I do know know of a lossless insert of JPEG to TIFF images.
> If there was it would proably make a good IM delegate (external
> converter program).
>
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?
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