About plot(..., linewidth=...), granularity and alpha

Hello all,

I’m playing with FFT currently.

Here is the display under scilab (from wich
I’m proting the code to matplotlib)

image001.png

And the display under matplotlib :

image002.png

Display under matplotlib is done via: plot(freq,
abs(FreqI[0:len(FreqI)/2+1]), ‘b’, linewidth=.25)

To match let say “granularity”
of scilab I had to add linewidth=.25.

What is the best linewidth value there, I
mean to use 1 pixel for each frequency?

.25 is not so bad but still blurry.

.1 gives excellent result but seems like if
I have applied an alpha value:

image003.png

Is it possible to get .1 result but with
more stronger colors (without alpha effect?)?

Cheers,

Laurent

Laurent Dufrechou wrote:

Hello all,

I’m playing with FFT currently.

Here is the display under scilab (from wich I’m proting the code to matplotlib)

And the display under matplotlib :

Display under matplotlib is done via: plot(freq, abs(FreqI[0:len(FreqI)/2+1]), 'b', linewidth=.25)

To match let say “granularity” of scilab I had to add linewidth=.25.

What is the best linewidth value there, I mean to use 1 pixel for each frequency?

.25 is not so bad but still blurry.

.1 gives excellent result but seems like if I have applied an alpha value:

Is it possible to get .1 result but with more stronger colors (without alpha effect?)?

I suspect that what you are calling the alpha effect (or the blurry effect with 0.25) is really antialiasing, which scilab likely does not have. You can turn it off by adding the aa=False kwarg setting to your plot command.

Eric

···

Cheers,

Laurent

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