logarithmic plot function failure

Hello,

After reading a certain article connected to pseudocoloring a grey image with HSI map color I wanted to try it on my own but the result didnt meet my expectations, the problem is logarithmic function. Article states that impying these formulas:

I should get plot:

my code:

map = zeros(256,3);

x = 1:256;

map(:,1) = 1/2 - 1/2*sqrt(1 - (x/256).*(x/256));

map(:,2) = 0.8;

map(:,3) = log(((x+1)/(256+1)));

figure;plot(x,map);

Answer 1

[Jan]

Where do you see a failure? If the argument of the logarithm is smaller then e (which is exp(1)), the output must be negative. In the posted diagram I (the blue line) starts at 0, while this is not possible for:

log((x+1) / (256 + 1))

So the actuial problem is, that your expectations do not match the posted formula.

[iMatten]

yes, I agree with that. I was wondering if there is any trouble with formula or I was doing something wrong.

I hadn't thought that might be a mistake in this article. Then what formula for "I: component that would be?