|
Hi,
I've recently started experimenting with the
littlecms package for possible use in an image-editing program I've been
writing. This package is much appreciated, and would appear to be just what I
need. However, I've noticed three "features" so far, in the day and a half I've
been using it. These problems have to do with tags, and the opening and saving
of profiles for embedded use:
(1) It seems the _cmsSaveProfile() and
_cmsSaveProfileToMem() functions have some issues. If you call these functions,
the profile is corrupted, because the tag directory gets damaged. More
specifically, the TagSizes[] array internal to the lcms profile structure gets
modified during the save operations, (specifically in the SaveTags() function),
rendering the tags unusable.
It seems to me that saving a profile should not
render it unusable for further operations.
(2) Also, another problem I've encountered when
using embedded profiles: A profile created with _cmsOpenProfileFromMem() cannot
be saved properly with _cmsSaveProfile() or _cmsSaveProfileToMem(). Basically,
the tags created with _cmsOpenProfileFromMem() are not in the right form for
saving, so they get dropped, resulting in a corrupt profile. So, for example, if
I want to "copy" a profile from a tiff file I've opened, back to the tiff file
after editing, I have to copy the raw buffer I obtained from
_cmsOpenProfileFromMem(), rather than try to save the profile using the handle
created from _cmsOpenProfileFromMem().
(3) There appears to be no way to copy a profile in
memory, at least with a convenient function call. So if you wish to save a
profile to a memory buffer (for embedding in tiff and jpeg files) or to a file,
but still continue to use that profile for internal color conversions, you
can't, because the profile gets corrupted, and you can't even make a copy of it
beforehand.
One workaround I've come up with is to follow
any call to _cmsSaveProfileToMem() with a call to _cmsOpenProfileFromMem(),
using the same buffer. Then the profile is usable --- to a point. You can use it
alright, you just can't ever save it again! (Due to issues #1 and
#2.)
Am I doing something wrong, or are these legitimate
bugs?
Otherwise, the package seems to be working
smoothly, and is very much appreciated. It's some of the cleanest open source
code I've encountered, as far as readability is concerned. And it compiles with
no errors or warnings, which is always a good sign.
Thanks,
Bryan Flamig
|
