在Matlab中手动将RGB转换为HSV时出现怪异现象 [英] Weird phenomenon when converting RGB to HSV manually in Matlab

问题描述

我编写了一个小的Matlab函数，该函数使用RGB图像，并根据找到的转换公式将其转换为HSV 此处.

I have written a small Matlab funcion which takes an image in RGB and converts it to HSV according to the conversion formulas found here.

问题是，当我将其应用于色谱时，色谱中有一个割线，并且某些值是错误的，请参见图像(为了使比较容易，我已使用内部的hsv2rgb()函数将其转换回RGB Matlabs自己的函数rgb2hsv()不会发生这种情况，但是我找不到我做错了什么.

The problem is that when I apply this to a color spectrum there is a cut in the spectrum and some values are wrong, see images (to make the comparison easier I have used the internal hsv2rgb() function to convert back to RGB. This does not happen with Matlabs own function rgb2hsv() but I can not find what I have done wrong.

这是我的职责

function [ I_HSV ] = RGB2HSV( I_RGB )
%UNTITLED3 Summary of this function goes here
%   Detailed explanation goes here

[MAX, ind] = max(I_RGB,[],3);
if max(max(MAX)) > 1
    I_r = I_RGB(:,:,1)/255;
    I_g = I_RGB(:,:,2)/255;
    I_b = I_RGB(:,:,3)/255;
    MAX = max(cat(3,I_r, I_g, I_b),[],3);
else
    I_r = I_RGB(:,:,1);
    I_g = I_RGB(:,:,2);
    I_b = I_RGB(:,:,3);
end
MIN = min(cat(3,I_r, I_g, I_b),[],3);
d = MAX - MIN;

I_V = MAX;
I_S = (MAX - MIN) ./ MAX;
I_H = zeros(size(I_V));

a = 1/6*mod(((I_g - I_b) ./ d),1);
b = 1/6*(I_b - I_r) ./ d + 1/3;
c = 1/6*(I_r - I_g) ./ d + 2/3;
H = cat(3, a, b, c);

for m=1:size(H,1);
    for n=1:size(H,2);
        if d(m,n) == 0
            I_H(m,n) = 0;
        else
            I_H(m,n) = H(m,n,ind(m,n));
        end
    end
end

I_HSV = cat(3,I_H,I_S,I_V);


end

原始光谱 转换后的光谱

Original spectrum Converted spectrum

推荐答案

错误在于我简化了a，b和c的计算.将其更改为以下内容可以解决该问题.

The error was in my simplification of the calculations of a, b, and c. Changing it to the following solved the problem.

function [ I_HSV ] = RGB2HSV( I_RGB )
%UNTITLED3 Summary of this function goes here
%   Detailed explanation goes here

[MAX, ind] = max(I_RGB,[],3);
if max(max(MAX)) > 1
    I_r = I_RGB(:,:,1)/255;
    I_g = I_RGB(:,:,2)/255;
    I_b = I_RGB(:,:,3)/255;
    MAX = max(cat(3,I_r, I_g, I_b),[],3);
else
    I_r = I_RGB(:,:,1);
    I_g = I_RGB(:,:,2);
    I_b = I_RGB(:,:,3);
end
MIN = min(cat(3,I_r, I_g, I_b),[],3);
D = MAX - MIN;

I_V = MAX;
I_S = D ./ MAX;
I_H = zeros(size(I_V));

a = 1/6*mod(((I_g - I_b) ./ D),6);
b = 1/6*((I_b - I_r) ./ D + 2);
c = 1/6*((I_r - I_g) ./ D + 4);
H = cat(3, a, b, c);

for m=1:size(H,1);
    for n=1:size(H,2);
        if D(m,n) == 0
            I_H(m,n) = 0;
        else
            I_H(m,n) = H(m,n,ind(m,n));
        end

        if MAX(m,n) == 0
            S(m,n) = 0;
        end
    end
end

I_HSV = cat(3,I_H,I_S,I_V);

end

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