Update the internal thumbnail of a jpg file ?

[spok]

I have a jpeg file which I access and modify through a PixelPacket * pointer.
When I save the file after modification, the thumbnail contained inside the file is not updated.
Is there any method which allows to update the internal thumbnail of a jpg file ?

The same program with a tif file, works great and update the thumbnail contained inside the tif file automatically...

[magick]

The thumbnail is part of the EXIF profile. ImageMagick only updates the resolution of the EXIF profile. For the thumbnail you'll need another utility.

[spok]

The thumbnail is part of the EXIF profile. ImageMagick only updates the resolution of the EXIF profile. For the thumbnail you'll need another utility.

Thanks for the answer. Do you know any library I can use for this ?