I think the second one is better. I also use this function. For the difference, this might be helpful:

rgb2lab: Convert RGB to CIE 1976 L*a*b* https://www.mathworks.com/help/images/ref/rgb2lab.html

makecform: Create color transformation structure. https://www.mathworks.com/help/images/ref/makecform.html

applycform: Apply device-independent color space transformation https://www.mathworks.com/help/images/ref/applycform.html?searchHighlight=makecform&s_tid=doc_srchtitle

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1st example:

rgb = imread('peppers.png'); cform = makecform('srgb2lab'); lab = applycform(rgb,cform);

=> Convert RGB image to L*a*b*, assuming input image is sRGB (not RGB).

2nd example:

lab = rgb2lab(rgb)

lab = rgb2lab(rgb,Name,Value)

In MATLAB guide, they also recommend to use rgb2lab:

In makecform(arg), the argument 'srgb2lab': Use rgb2lab instead.

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See Steve's blog for lots and lots of info: http://www.mathworks.com/search/site_search.html?q=color+space&c[]=blogs

I use rgb2lab() to convert to CIE LAB color space whenever I need relative, quick and dirty, kind of color space conversion. Never use JPG images for image analysis. It's no wonder the values are different. JPG will destroy the image to various degrees. Use PNG instead.

All of those are "book" formulas. They will not give you the "true" LAB like you'd get from a spectrophotometer.Most of the time I use calibrated digital color imaging because I need the "true" LAB values out, not some arbitrary ones. But that's a much higher level of sophistication that you probably want to do.

there is no Matlab code in that case. so you must program the problem

For converting RGB to Lab, kindly see the link:

https://in.mathworks.com/matlabcentral/answers/47601-how-to-convert-rgb-to-cie-lab-color-space

Sarah,

I usually use:

colorTransform = makecform('srgb2lab'); lab = applycform(rgbImage, colorTransform);

but u can also use the second one ( rgb2lab() ) I can see u already used the imshow(). u can also just check its values in the variable editor in the workspace. Otherwise all you get is a new variable.

I think the second one is better. I also use this function. For the difference, this might be helpful:

rgb2lab: Convert RGB to CIE 1976 L*a*b* https://www.mathworks.com/help/images/ref/rgb2lab.html

makecform: Create color transformation structure. https://www.mathworks.com/help/images/ref/makecform.html

applycform: Apply device-independent color space transformation https://www.mathworks.com/help/images/ref/applycform.html?searchHighlight=makecform&s_tid=doc_srchtitle

---

1st example:

rgb = imread('peppers.png'); cform = makecform('srgb2lab'); lab = applycform(rgb,cform);

=> Convert RGB image to L*a*b*, assuming input image is sRGB (not RGB).

2nd example:

lab = rgb2lab(rgb)

lab = rgb2lab(rgb,Name,Value)

In MATLAB guide, they also recommend to use rgb2lab:

In makecform(arg), the argument 'srgb2lab': Use rgb2lab instead.

---

See Steve's blog for lots and lots of info: http://www.mathworks.com/search/site_search.html?q=color+space&c[]=blogs

I use rgb2lab() to convert to CIE LAB color space whenever I need relative, quick and dirty, kind of color space conversion. Never use JPG images for image analysis. It's no wonder the values are different. JPG will destroy the image to various degrees. Use PNG instead.

All of those are "book" formulas. They will not give you the "true" LAB like you'd get from a spectrophotometer.Most of the time I use calibrated digital color imaging because I need the "true" LAB values out, not some arbitrary ones. But that's a much higher level of sophistication that you probably want to do.