Working in CIE Lab color space

You can convert image to the CIE Lab color space, then split the planes, work with the planes independently (as grey images) and recompose the image merging all planes.

cout << "Split and merge in CIE Lab color space:" << endl;

const char * filenameIn = "../../datas/planet.jpg";
cout << ".Loading RGBub image file: " << filenameIn << endl;
ImageVariant image(filenameIn);
bool bSuccess = image.IsValid();

cout << ".Change image color space and resolution to CIE Lab floating point" << endl;
bSuccess = image.ChangePixelFormat(PF_Labf);

cout << ".Split planes: L, a and b" << endl;
ImageVariant L, a, b;
bSuccess = image.Split(L, a, b);

cout << ".Blur L plane applying Gaussian filter of 1.5 radius" << endl;
bSuccess = L.ApplyGaussian(1.5);

cout << ".Sharpen L plane" << endl;
bSuccess = L.ApplySharpenMore();

cout << ".Mul a plane by 1.7" << endl;
bSuccess = a.Mul(1.7);

cout << ".Mul b plane by 0.8" << endl;
bSuccess = b.Mul(0.8);

cout << ".Recompose Lab image merging L,a and b planes" << endl;
image = ImageVariant(L, a, b, CS_CIE_Lab);

cout << ".Change image color space and resolution to RGBub before saving" << endl;
bSuccess = image.ChangePixelFormat(PF_RGBub);

const char * filenameOut = "output/planet-Lab.jpg";
cout << ".Save image as " << filenameOut << " ";
bSuccess = image.Save(filenameOut);
cout << (bSuccess? "successfull" : "failed") << endl;

Output:

Split and merge in CIE Lab color space:
.Loading RGBub image file: ../../datas/planet.jpg
.Change image color space and resolution to CIE Lab floating point
.Split planes: L, a and b
.Blur L plane applying Gaussian filter of 1.5 radius
.Sharpen L plane
.Mul a plane by 1.7
.Mul b plane by 0.8
.Recompose Lab image merging L,a and b planes
.Change image color space and resolution to RGBub before saving
.Save image as output/planet-Lab.jpg successfull

planet.jpg

planet-Lab.jpg

You can also convert image to the CIE Lab color space, and directly process the planes independently.

  cout << "Working in CIE Lab color space:" << endl;

  const char * filenameIn = "../../datas/planet.jpg";
  cout << ".Loading RGBub image file: " << filenameIn << endl;
  ImageVariant image(filenameIn);
  bool bSuccess = image.IsValid();
  
  cout << ".Change image color space and resolution to CIE Lab floating point" << endl;
  bSuccess = image.ChangePixelFormat(PF_Labf);
  
  cout << ".Blur L plane applying Gaussian filter of 1.5 radius" << endl;
  bSuccess = image.ApplyGaussian(1.5, 1., BF_Nearest, 1, CM_Channel0);
  
  cout << ".Sharpen L plane" << endl;
  bSuccess = image.ApplySharpenMore(1., 0.0, 1.0, 1.0, BF_Nearest, 1, CM_Channel0);
  
  cout << ".Mul a plane by 1.7" << endl;
  bSuccess = image.Mul(1.7, CM_Channel1);
  
  cout << ".Mul b plane by 0.8" << endl;
  bSuccess = image.Mul(0.8, CM_Channel2);
  
  cout << ".Change image color space and resolution to RGBub before saving" << endl;
  bSuccess = image.ChangePixelFormat(PF_RGBub);

  const char * filenameOut = "output/plane-Lab.jpg";
  cout << ".Save image as " << filenameOut << " ";
  bSuccess = image.Save(filenameOut);
  cout << (bSuccess? "successfull" : "failed") << endl;

Output:

Working in CIE Lab color space:
.Loading RGBub image file: ../../datas/planet.jpg
.Change image color space and resolution to CIE Lab floating point
.Blur L plane applying Gaussian filter of 1.5 radius
.Sharpen L plane
.Mul a plane by 1.7
.Mul b plane by 0.8
.Change image color space and resolution to RGBub before saving
.Save image as output/plane-Lab.jpg ok