>1) First, I want to deal with RGB-24-bit, RGB-48-bit and RGB float (also known as HDR) images >2) To process such images, I need to convert them to Yxy or CIE Lab color space
¿Why do you think you need do that? >3) Then, I need to apply my greyscale algorithms to the Y (Yxy) or to the L (CIE Lab) component >4) I then have to convert back the transformed image to a RGB color space (RGB 24-/48-bit or RGB float) >5) for HDR images, once I have a transformed RGB float image, I can apply a tone mapping algorithm and convert to 48-bit (or 24-bit) The problems I have are the following : --------------------------------------- >A) If I need to write a RGB2XYZ matrix to convert my images, what matrix should I use ? It up of the RGB space you assume you want to use. sRGB use a matrix, AdobeRGB other, the space of the camera you use, other. >My images are taken from unknown files (LDR, HDR float) or from unknown camera (JPEG 24-bit or RAW converted to 48-bit, no profile attached), so I am afraid, if the data are not raw and it is RGB it has a gamma correction applied. So it is not lineal >do I have to assume they have linear RGB color values or do I have to >assume that they use a sRGB color model or do I need to apply a gamma >correction before the transformation ? Probably what comes in RGB from a camera arrives in... RGB. The sRGB of the camera file is only a label, the data are not converted from the "inknown" color space of the camera to the sRGB. Only labeled. So you can asume there is no sRGB data actually. I think. >In the second case (sRGB) or >third case (gamma correction), the transformation matrix is far more >complex to calculate (from a computationnal standpoint). Is this >computation really needed ? Of course, that is the aim of LittleCMS (I supose) ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid0944&bid$1720&dat1642 _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
