Average value of H in HSV of a picture

I was asked to divide a jpg picture to several parts with equal area. And I need to get average value of H in HSV of the picture. I want to know how to get the average value of H.

Answer 1

[Jan]

Calculate the mean over 4x4 blocks:

RGB = rand(100, 200, 3);
HSV = rgb2hsv(RGB);
H   = HSV(:, :, 1);
meanH = mean(H(:));
BlockH = reshape(H, 4, 25, 4, 50);
meanBlockH = reshape(sum(sum(H, 1), 3), 25, 50) / 16;

Care about the overflow, when you use UINT8 images.

[Xiaochao]

Thank you. It helps me a lot.

[Xiaochao]

I have a picture of 640*480 pixels. I want to divide it to 16*16 blocks and get average value H of every block. The result shoud be a 40*30 array. But I tried mean function, the result always is a 1*16 array.

[Jan]

Exactly as shown in my example:

BlockH = reshape(H, 16, 40, 16, 30);
meanBlockH = reshape(sum(sum(H, 1), 3), 40, 30) / 256;

Answer 2

[Sean de Wolski]

doc blockproc

[Xiaochao]

Thank you very much, I will try this functio