how lab vector differe from lab values

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Hi guysss..

I am working with segmentation now...i need to convert l a b space color values to l a b vector...how its possible..??what is the difference bwn lab values and lab vector??how tp represent lab space vector??

Posted 15-Sep-15 6:26am

silvsten john

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CHill60 15-Sep-15 12:37pm

What have you tried? Where are you stuck?
Use the full words not your own made up words ("bwn", "tp", "guysss")

silvsten john 16-Sep-15 0:40am

Sorry for that...i can give more detail about pblm...nw i am working with slic super pixel segmentation

As this algorithm says..convert whole image pixel RGB values to CIE LAB..i converted RGB to LAB....nw i have set of LAB values for all the pixels in my image ..

The next step is i should find Gradient of lab vector.this is the equation to to find image gradient in lab color space...

G(x,y)=I(x+1,y)-I(x-1,y)+I(x,y+1)
-I(x,y-1).

here I(x,y) denotes lab vector at x,y position..

then my doubt is as i said i have set of l a b values(in double format)..how will i apply these values in this gradient equation as lab vector.

..expecting u understand it..

2 solutions

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User 11060979 · Accepted Answer · 2015-09-15T07:13:00

Solution 2

First try to understand what CIELAB means. Than you will find that your "so called" Lab* Values are the components of a Lab* Vector in the Lab* Colorspace

In very short:
Lab* is a (three dimensinal) colour space. The "*" Comes from history to make a clear difference between the CIE-LAB space and others like Hunter Lab.

See wiki:
CIEAB>[^]

Here you can find all the formulas (including explanation) to convert from e.g. sRGB to XYZ etc.
http://www.brucelindbloom.com/[^]

[EDIT]
Sorry for bad layout, I don't know how to do it better ;)

That is simple vector addition/substratction.You do this component whise.
E.g. (and sorry for the bad representation)

       3    // L*
lab_1= 4    // a*
       2    // b*

       7
lab_2= -1
       1
                     3+7       10
than lab_1 + lab_2=  4+(-1)  =  3
                     2+1        3


And in your case you have simply 4 lab vectors from the source picture you need to calculate:
according to G(x,y)= lab_1 - lab_2 + lab_3 - lab_4 to get the Lab* value in your target gradient.

[/EDIT]

Posted 15-Sep-15 7:13am

User 11060979

Updated 15-Sep-15 23:01pm

v4

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silvsten john 16-Sep-15 0:50am

First ...thanks for ur reply..

Sir actually i converted rgb to l a b values.
i have l a b values corresponding each pixel in the image..

.i can give more detail about pblm...nw i am working with slic super pixel segmentation

As this algorithm says..convert whole image pixel RGB values to CIE LAB..i converted RGB to LAB....nw i have set of LAB values for all the pixels in my image ..

The next step is i should find Gradient of lab vector.this is the equation to to find image gradient in lab color space...

G(x,y)=I(x+1,y)-I(x-1,y)+I(x,y+1)
-I(x,y-1).

here I(x,y) denotes lab vector at x,y position..

then my doubt is as i said i have set of l a b values(in double format)..how will i apply these values in this gradient equation as lab vector...???

[no name] 16-Sep-15 4:28am

I tried to explain it, see modified answer. Sorry for bad layout there.

CPallini 16-Sep-15 5:14am

My 5.

[no name] 16-Sep-15 5:23am

Thank you very much.

silvsten john 16-Sep-15 6:02am

Thank you very much sir

Then How we can view/output cie lab color mode in image..??

[no name] 16-Sep-15 6:09am

You are welcome.
Look at http://www.brucelindbloom.com/[^] how to calculate Lab back to sRGB, that is the easiest way.

silvsten john 16-Sep-15 7:15am

Ok noted....sir then as i said i working on an copy move forge detection scheme project...in that project the preliminary step is to segment the image by super pixel segmentation....that is what i am doing nw..bt i am taking too much tym to do even the first step this slic based superpixel segmentation...

My doubt is should we write our own code for this modules (eg.superpixel segmentation..).or will i get any open source tools to find
Super pixel segmentation in c# .net ..(bec i downloaded slic implementation in vc++ from a site..bt vc++ does not creating dll files thatswhy i couldnot add as reference to my c# project)

[no name] 16-Sep-15 7:41am

You downloaded the c++ source? Complete? If yes maybe simply code it in c# or migrate it to Visual C++ .NET. For the later you can find some Information on MSDN.

Sergey Alexandrovich Kryukov · Accepted Answer · 2015-09-15T06:41:00

Solution 1

This is a plain wrong question, "how differ"? Just learn how this color space works: https://en.wikipedia.org/wiki/Lab_color_space[^].

Most questions about "difference" are inherently invalid. If you didn't get it yet, try to tell use the "difference" between apple and Apple. :-)

—SA

Posted 15-Sep-15 6:41am

Sergey Alexandrovich Kryukov

Comments

[no name] 15-Sep-15 13:40pm

Wiki is ok for start a 5. I added also bruce lindbloom in Answer 2. He gives a lot of explanations also.

silvsten john 16-Sep-15 0:39am

First ...thanks for ur reply sir..i can give more detail about pblm...nw i am working with slic super pixel segmentation

As this algorithm says..convert whole image pixel RGB values to CIE LAB..i converted RGB to LAB....nw i have set of LAB values for all the pixels in my image ..

The next step is i should find Gradient of lab vector.this is the equation to to find image gradient in lab color space...

G(x,y)=I(x+1,y)-I(x-1,y)+I(x,y+1)
-I(x,y-1).

here I(x,y) denotes lab vector at x,y position..

then my doubt is as i said i have set of l a b values(in double format)..how will i apply these values in this gradient equation as lab vector.

..hope u understand my doubt sir...thank u