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stixoffire
Beginner
26 Views

IPP usage for Jpeg Imaging

I would like to know several things about the functionality of the IPP and Jpeg encoding.

1: I would like to know if IPP will allow for transforming the colorspace of the Jpeg from YCbCr to Lab values?

2: Can it do this conversion (referred toin Question 1 without a loss of color data - i.e. when I recode the image Y parameter as an L parameter..and the a and b components as wellwill I end up with a Jpeg that was opened and then recompressed - losing more of the original image data?

3: Can I check for the whitepoint of the Jpeg?

4: Can I modify this whitepoint - and perform Question 1, with no ill affects as referred to in Question 2?

If these are all possible - could I see a quick and dirty brief sample ... does not need to be completely detailed just a guide line for using the code..

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2 Replies
Vladimir_Dudnik
Employee
26 Views

Hello,

Usually, JPEG encoders do convertion from RGB to YCbCr color space because this improve compression ratio. In your particular case, when you have image in LAB color space on input you may set input color JC_UNKNOWN, so encoder will not do any color convertion on that. Then at decoding stage you also need to set output color as JC_UNKNOWN to disable color convertion step. We do not have sample code for that. What do you mean under check for whitepoint?

Regards,
Vladimir

stixoffire
Beginner
26 Views

My problem is that image on input is not in Lab space - I want to convert to that space using IPL. Normally Jpeg is in YCbCr - at Illuminant D65 - I want mine to be in Lab D50. The normal process of conversion would be RGB to XYZ - White reference change (D65 to D50 ) then from XYZ to Lab function. How would this be accomplished in IPL 6.0

Hello,

Usually, JPEG encoders do convertion from RGB to YCbCr color space because this improve compression ratio. In your particular case, when you have image in LAB color space on input you may set input color JC_UNKNOWN, so encoder will not do any color convertion on that. Then at decoding stage you also need to set output color as JC_UNKNOWN to disable color convertion step. We do not have sample code for that. What do you mean under check for whitepoint?

Regards,
Vladimir