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• How to make FuncAnimation animations faster ?

  12 juin 2021, par Zenitsu

  The code I have written is for a Lorrenz Attractor in Python. It shows how a number of random points evolves according to lorrenz equtions and falls into the lorrenz attractor. I did get satisfactory results when I ran the code, but ran into problems while saving the animation as a gif or mp4 file. Python and my text editor started crashing when I tried saving them. I want to know if the code could be simplified or maybe made more effective in some way. Thankyou for helping !!

  


  # Importing all the necessary modules

import matplotlib.pyplot as pl
from mpl_toolkits.mplot3d import Axes3D
from matplotlib.animation import FuncAnimation
import matplotlib.animation as animation
import matplotlib.cm as cm
import numpy as np

#Writer = animation.writers['ffmpeg']
#writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)

fig = pl.figure(figsize=(35,35))
ax = pl.axes(projection="3d") 
fig.set_facecolor('black')
ax.set_facecolor('black') 
ax.w_xaxis.pane.fill = False
ax.w_yaxis.pane.fill = False
ax.w_zaxis.pane.fill = False
ax.get_proj = lambda: np.dot(Axes3D.get_proj(ax), np.diag([2, 2, 2, 1.3]))
ax.grid(False)
ax.set_axis_off()

# B has the values of sigma, rho and beta used in the lorrenz equations
B =[10,28,8/3]
# t is the dt time element
t = 0.001
# The number of points 
num_points = 20

# These three list will store all the x, y and z position of all the points
X_data = []
Y_data = []
Z_data = []

for i in range(0,num_points,1):
        x_data = []
        y_data = []
        z_data = []
        x , y , z = np.random.uniform(-25,25),np.random.uniform(-25,30),np.random.uniform(0,60)
        for i in np.arange(0,10,t):

                dx = B[0]*(y-x)*t
                dy = (x*(B[1] - z)-y)*t
                dz = (x*y-B[2]*z)*t

                x+=dx
                y+=dy
                z+=dz

                x_data.append(x)
                y_data.append(y)
                z_data.append(z)
        X_data.append(x_data)
        Y_data.append(y_data)
        Z_data.append(z_data)

color = cm.rainbow(np.linspace(0,1,num_points))

def animate(i):
        pl.cla()

        for j in range(0,num_points,1):
                ax.set_axis_off()
                ax.plot3D(X_data[j][2*i:10*i],Y_data[j][2*i:10*i],Z_data[j][2*i:10*i],linewidth=0.5,color=color[j])
                ax.plot3D(X_data[j][10*i],Y_data[j][10*i],Z_data[j][10*i],marker=".",color=color[j],markersize=3)
                ax.set_xlim([-30,30])
                ax.set_ylim([-30,30])
                ax.set_zlim([0,60])

        ax.view_init(0,i/2) 

ani = FuncAnimation(fig,animate,repeat=False,interval=100,frames=600)

# Commented out the bottom part so that i can see it before saving

#ani.save('Lorrenz_Attractor.mp4', writer=writer)

#writer = animation.PillowWriter(fps=10)  
#ani.save("Lorrenz_Attractor.gif", writer=writer)

pl.show()


  


• how to change ffmpeg xstack background color

  17 août 2021, par Abdelsalam ElTamawy

  I creating a 2x2 grid of videos but only had 3 videos. So I created an xstack of these 3 videos. The bottom right corner does not get a video. This causes it to be left to FFmpeg default colour.

  


  Here is the command I use to create the video mosaic :

  


  ffmpeg -i TEST.mkv -i TEST.mkv -i TEST.mkv -filter_complex "
[0:v] scale=960x540 [a0];
[1:v] scale=960x540 [a1];
[2:v] scale=960x540 [a2];
[a0][a1][a2] xstack=inputs=3:layout=0_0|0_h0|w0_0[out]"
 -map "[out]" -f matroska - | ffplay -


  


  

  


  How can I make the green corner black or any other colour ?

  


  I'm using FFmpeg version 4.4

  


• ImageMagick to crop image based on based on rectangular border color

  3 septembre 2021, par Alvie Mahmud

  I have some images that I would like to crop but hopefully via command line rather than doing each one manually.

  


  I would like to crop the image (I've cropped top half, desaturated other colours and split frames with ffmpeg) based on where there is a border of a certain color (#31393C in this case). For example, I would like this image :

to be cropped like this :
  


  


  I have tried some commands but they aren't working for me unfortunately.

  


  convert image.jpg -bordercolor "#31393C" -border 2x2 -fuzz 10% -trim output.jpg


  


  I have also tried to make the parts that aren't #31393C to be filled with white and then cropping which may potentially work as a solution as I want to improve the ability to use OCR :

  


  convert image.jpg -fill white -fuzz 11% +opaque "#31393c" result.jpg
convert result.jpg -bordercolor white -border 10x10 -fuzz 10% -trim output.jpg


  


  which works somewhat but not perfectly :