Re: [Lcms-user] Littlecms with ImageMagick - howto?

[Bob F. <bfr...@si...>]

On Thu, 18 Aug 2005, Michal Paczek wrote:
>> On Thu, 23 Jun 2005, Michal Paczek wrote:
>> 
>>> Does anybody know how to use Littlecms functions in ImageMagick?
>>> How to convert colorspace of  Image object (c code api) with defined 
>>> profile (ICC) ?
>> 
>> 
>> This is done via a ProfileImage() function.  The profile is supplied as an 
>> in-memory BLOB.  If the image does not already have a ICC profile attached 
>> to it, the call to ProfileImage() simply attaches to supplied profile to 
>> the image and no transformations are done to the pixels.  If the image 
>> already has an ICC profile, then ProfileImage() invokes the CMS transform 
>> based on the two profiles to convert the image pixels to the target space.
>> 
>> The functioning is really simple and is definitely not a "system" but it 
>> works well in the hands of a CMS expert. 
>
> I still have problem with colorspace conversion and don't know how to load 
> ICC prifile from file. Which function does that thing? What is exactly datum 
> argument in ProfileImage() funciton?
> Can you give me some example how to use this function and make ColorSpace 
> conversion...?

I do not have time to supply a complete code example, but I can 
provide some more hints.  The user of ProfileImage() needs to copy the 
entire ICC profile from disk into memory somehow.  For example, this 
may be accomplished via fopen() & fread().  The 'datum' argument is 
the address in memory where the profile has been loaded, and the 
length argument is the size of the profile in memory.

In addition to ProfileImage(), ImageMagick provides SetImageProfile() 
which can be used to attach an initial profile to the image without 
applying any CMS transforms.

You can use GetImageProfile() to gain access to an existing profile 
which is attached to the image.  This is useful in order to know if 
the image already had a profile, or perhaps if you want to use the 
same profile for other things.

Bob
======================================
Bob Friesenhahn
bfr...@si..., http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/