Converting an OpenCV BGR 8-bit Image to CIE L*a*b*
bgr, c++, colors, opencv, rgb
Solution
That's because L value is in range [0..255] in OpenCV. You can simply scale this value to needed interval ([0..100] in your case).
Problem
I am trying to convert a given `Mat` representing an RGB image with 8-bit depth to Lab using the function provided in the documentation: ``` cvtColor(source, destination, <conversion code>); ``` I have tried the following conversion codes: ``` CV_RGB2Lab CV_BGR2Lab CV_LBGR2Lab ``` I have received bizarre results each time around, with an "L" value of greater than 100 for some samples, literally <107, 125, 130>. I am also using Photoshop to check the results - but given that 107 is beyond the accepted range of 0 ≤ L ≤ 100, I can not comprehend what my error is. Update: I'll post my overall results here: Given an image (Mat) represented by 8-bit BGR, the image can be converted by the following: ``` cvtColor(source, destination, CV_BGR2Lab); ``` The pixel values can then be accessed in the following manner: ``` int step = destination.step; int channels = destination.channels(); for (int i = 0; i < destination.rows(); i++) { for (int j = 0; j < destination.cols(); j++) { Point3_<uchar> pixelData; //L*: 0-255 (elsewhere is represented by 0 to 100) pixelData.x = destination.data[step*i + channels*j + 0]; //a*: 0-255 (elsewhere is represented by -127 to 127) pixelData.y = destination.data[step*i + channels*j + 1]; //b*: 0-255 (elsewhere is represented by -127 to 127) pixelData.z = destination.data[step*i + channels*j + 2]; } } ```