topic Contrast measurement in Intel® Integrated Performance Primitives

Contrast measurement

sunderam08 — Thu, 16 Jun 2005 14:30:25 GMT

Hi people,
I am trying to measure for images. I am referring to this paper(http://diuf.unifr.ch/courses03-04/imaging/simoncelli.pdf).
The paper suggest that i find luminance first and then i find contrast.
The paper says that luminance could be found by calculating mean intensity.(image is considered as signal).
And then finally contrast could be found by reomving the mean intensity from the signal.
And using the standard deviation (the square root of variance) as an estimate of the signal contrast. An unbiased estimate in discrete
form is given by formula.

My question are
1. Can i find log average luminance value to calculate luminance
2. How do represent the image in terms of signal to do the calculation.
Any suggestions?
thanks
Jay

Re: Contrast measurement

Vladimir_Dudnik — Wed, 27 Jul 2005 22:35:27 GMT

Hi,

There is no need to do (2) all necessary functions present in ippIP domain.

1) mean removal:

ippiMean_32f_C1R( pSrc, srcStep, RoiSize, &Mean64f, ippAlgHintAccurate );

Mean32f = (Ipp32f)Mean64f;

ippiSubC_32f_C1IR( Mean32f, pSrc, srcStep, RoiSize );

variance:

ippiNorm_L2_32f_C1R( pSrc, srcStep, RoiSize, &NormL2, ippAlgHintAccurate );

Regards,
Vladimir