luminance component of an image

Hi, I have a frame of a vedio sequence I which is a 288*532 double. How can I extract only the luminance component? Thanks.

Answer 1

[Mark Sherstan]

Run the following:

I = imread('test.png');
J = rgb2gray(I);

rgb2gray uses the same formual which is used to calculate luminance (to 3 decimal places the formula is):

0.299 * R + 0.587 * G + 0.114 * B

[az]

I1 = vcif2('b_cif.yuv',1);

Thank you Mark,

this is my Image which is a frame of a yuv vedio file. now how can I comvert it to png first?

[Mark Sherstan]

The example I posted is just for one image. If you have a video it would look something like this:

v = VideoReader('someVideo.mp4');

while hasFrame(v)
    video = readFrame(v);
    J = rgb2gray(video);
end

I am not familiar with that vcif2 (is it a custom function?) but if you have read in an image already you could directly apply:

J = rgb2gray(I2);

It looks like you might be in a different colorspace so try applying this first:

I2 = ycbcr2rgb(I2)

[az]

Thank you this is what I got. Please see the attachment.

[Mark Sherstan]

please provide the original image, video, and any given functions.

Answer 2

[az]

Hello Mark I trief to sent you the tennis_cif.yuv but the file is more than 30 K even in zipped condition. is there any way I can attach that big file? Thank you for your efforts.

[Image Analyst]

Just attach the one frame, not the entire video. One frame will certainly be small enough to attach!

And explain why using rgb2gray() on the RGB image did not work.

Answer 3

[az]

All I can say you need to have this file to the vedio file path to open that in mathlab. Thanks.

Answer 4

[az]

Hello Mark, this the 'I_1' the one frame of the vedio. Thank you.