can lossless jpeg2000 format picture size be LESS than lossy jpeg2000 format of same picture

I have tiff image which i converted to jp2lossless and jp2lossy by using imwrite, but i found out that lossless version is having less size than lossy . Does this mean its correct conversion.

[Omer Moussaffi]

If Matlab is using the Jpeg2000 format specification, then it is possible. The lossy compression uses CDF9/7 filter, while the lossless compression uses the CDF5/3 filter. If the data in the image is mostly small scale linear gradients, it might be that the highpass part of the image is smaller with 'lossless' filter. Check out http://en.wikipedia.org/wiki/Wavelet_transform

Answer 1

[Ashish Uthama]

You could read both back and compare against the one your wrote out to verify the lossy/lossless nature for yourself.

The compression ratio of these methods are highly dependent on the particular image considered, it seems odd, but not impossible that a formats lossless version is smaller than its lossy version for a particular image. JPEG2000 has quite a few parameters other than just lossy/lossless (have a look at the imfinfo output), maybe difference in other properties of the format result in the size difference.

Though, I would be very surprised if its a large difference.

[nayana]

Thanks Ashish Uthama, i was wondering if my result is correct or not.