RGB2YCBCR image convertion

8 visualizaciones (últimos 30 días)
eng m
eng m el 9 de Mayo de 2021
Comentada: Walter Roberson el 9 de Mayo de 2021
i have this code i need to center Y,CB,CR around the center please show me what can i do.is truo?
I = imread('lena.tiff');
J2 = rgb2ycbcr((I));;
J2 =double(J2);
Y =((J2(:,:,1)));
cb=((J2(:,:,2)));
cr=((J2(:,:,3)));
Y=Y-128;
cb=cb-128;
cr=cr-128
T=dctmatx(8);
  2 comentarios
DGM
DGM el 9 de Mayo de 2021
What do you mean "center" it? Cb and Cr should be centered about 128, since they're uint8. Also since they're uint8, subtracting 128 will truncate half the data.
eng m
eng m el 9 de Mayo de 2021
mean around to zero ,thanks

Iniciar sesión para comentar.

Respuesta aceptada

Walter Roberson
Walter Roberson el 9 de Mayo de 2021
Y=Y-128;
cb=cb-128;
cr=cr-128
If you read the documentation for rgb2ycbcr
Converted YCbCr color values, returned as a numeric array of the same size as the input.
  • If the input is double or single, then Y is in the range [16/255, 235/255] and Cb and Cr are in the range [16/255, 240/255].
  • If the input is uint8, then Y is in the range [16, 235] and Cb and Cr are in the range [16, 240].
  • If the input is uint16, then Y is in the range [4112, 60395] and Cb and Cr are in the range [4112, 61680].
So if you wanted to center Y around 0 you would subtract (235-16)/2 + 16 = 125.5 and for Cb and Cr you would subtract (240-16)/2 + 16 = 128
  3 comentarios
eng m
eng m el 9 de Mayo de 2021
thanks mr walter ,
and then can add again in the last code to repeat it ?
like this
Y = Y+125.5;
cb = cb+128;
cr = cr+128;
Walter Roberson
Walter Roberson el 9 de Mayo de 2021
yes

Iniciar sesión para comentar.

Más respuestas (1)

Image Analyst
Image Analyst el 9 de Mayo de 2021
Do you mean like
cb = cb - mean(cb(:));
cr = cr - mean(cr(:));
or possibly rescale so the max is at 127 and the min is at -127?
cb = rescale(cb, -127, 127);
cr = rescale(cr, -127, 127);
Those are two different things of course. They shift and scale the gamut by different amounts. I don't really know what your intent is, or why it's even necessary.
  4 comentarios
eng m
eng m el 9 de Mayo de 2021
please @Image Analyst i need to center y cb, cr around to zero
to do best compession and reduse storge .to do jpeg color image
Image Analyst
Image Analyst el 9 de Mayo de 2021
Editada: Image Analyst el 9 de Mayo de 2021
@eng m, as Walter discussed "centered" is not a clear cut definition. You need to describe what centered means. We can think of at least 3 definitions based on range, mean, or median. But it looks like you are all set now (whatever the definition you used was) because you've accepted an answer.

Iniciar sesión para comentar.

Categorías

Más información sobre Convert Image Type en Help Center y File Exchange.

Etiquetas

Productos


Versión

R2018a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by