MATLAB: Contrast vs brightness vs gamma

contrastImage Processing Toolbox

Please help, somebody in here can explain about picture i sent

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Those charts are a mapping of output gray level versus input gray level. A linear 45 degree line means that the output is the same as the input. Changing brightness is like raising or lowering the line so the output is brighter or darker than the input. Changing contrast is changing the slope of the line, which controls the range of the values, so like an input range of 100-120 (very narrow low contrast image) can be mapped to 0-255 (a much wider range and more contrasty image). Changing gamma is related to how much it emphasizes different ranges. If it goes up and flattens out (gamma charts on the left) the dark input range is expanded (making it more visible) while the bright contrast range is compressed. This is good for making dark parts of the image more visible. If the curve curves the other way, it makes the bright parts more visible and compresses the range of the dark parts of the image.

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MATLAB: Scalar vs matrix vs vector vs array?

Just like in mathematics, the only difference is their size.

MATLAB does not have special classes for scalars, vectors, matrices, or arrays: they are all arrays:

https://www.mathworks.com/help/matlab/matlab_prog/fundamental-matlab-classes.html

The usual definitions are:

array has any size RxCxPx....(x1x1x1x1...), it can be numeric/logical/char class
matrix is an array with size RxC(x1x1x1x1...)
vector is a array with size 1xC(x1x1...) or Rx1(x1x1x1...).
scalar is a array with size 1x1(x1x1x1...)

That is all.

MATLAB: Secd vs sec

Because your data ranges are different.

The area underneath the curve spanning -89.5:0.001:89.5 is approximately 180/pi times larger than the area underneath the curve spanning -pi/2:0.001:pi/2.

Your answers are correct, except you are using two different ranges. Surely the comparable range in degrees is -90:0.001:90

Note also that the step size for your degrees makes that calculation much more accurate than your radians range (which is using the same step size).

[edit] Compare apples with apples...

xd = -90:0.001:90;
yd = 1./secd(xd);
xr = xd * pi / 180;
yr = 1./sec(xr); 
% Use radians for x-axis in both calculations
zd = trapz(xr, yd)
zr = trapz(xr, yr)

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MATLAB: Scalar vs matrix vs vector vs array?

MATLAB: Secd vs sec

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