ImageMagick drawing a series of images with growing glow effect

Question

I'm learning ImageMagick. I want to create (with ImageMagick) a series of images that after using the command

convert -delay 0 -loop 0 frame*.gif final.gif

gives the result like the attached animated gif.

I want to program the series of commands myself, but I need a hint for which effects and drawing instructions will give me the most similar result, so I'm looking for something like:

• draw a circle
• blur it
• save the frame
• increase the radius of the circle
• repeat

but, probably the above is not enough.

Is this question very vague or can somebody give me a hint?

Answer 1

If you are in a shell environment (OSX or Linux) you could do something like this, which creates a series of blurred circles in ever-increasing radii and saves the image in appropriately named files...

for RAD in {10,20,30,40,50,60,70,80,90}; do convert -size 400x300 xc:black -fill cyan -stroke cyan -draw "translate 200,150 circle 0,0 $RAD,0" -blur 0x8 blur_circle$RAD.gif; done

To get fancier, you could add repeated blur operations, or more blur for the larger radii.

Then, as you suggest convert those to an animated gif:

convert -delay 0 -loop 0  blur_circle*.gif final.gif

EDIT

Working version closer to original "vision"

Here is a version that uses python to generate two circles, whose transparency varies on different time scales. With the current settings, transparency over time looks like this graph, but you can generate any lists of integer values to get different effects:

Here is the image produced by the program:

And here is the program itself:

#! /usr/bin/env python
""" Using imagemagick, generate a series of .gifs with fuzzy circles in them... 

When the program is done, create an animated gif with:
    convert -delay 0 -loop 0  blur_circle*.gif final.gif

(P.S. I know it is not 'convention' to capitalize variable names, but it makes
it easier to distinguish my definitions from built-ins)"""

import subprocess
import sys

CanvasW = 400
CanvasH = 400
CenterX = int(CanvasW/2)
CenterY = int(CanvasH/2)
InnerDia = 75
OuterDia = 155

BaseNameString = "blur_circles"

# play with overall blur level - 2 to 8
# this is in addition to the distance fuzzing
BlurLevel = '8'

# The following three lists must be the same length
# Transparency levels of the inner circle, ramping up and down 
InnerAlphaList = range(0,101,10)  + range(90,9,-20) + [5,0,0,0]
print "Inner:",len(InnerAlphaList),InnerAlphaList

# Transparency of the outer circle
OuterAlphaList = range(0,51,8) +  range(40,9,-12) + range(8,0,-2) + [0,0,0,0,0,0]
print "Outer:",len(OuterAlphaList), OuterAlphaList

# Add 100 so the file names get sorted properly?
NameNumberList = range(101, 101+len(InnerAlphaList))

# Changing the Euclidaan distance parameters affects how fuzzy the objects are

BaseCommand = '''convert -size {w}x{h} xc:black \
  -fill  "rgba( 0, 255,255 , {outal:0.1f} )" -stroke  none -draw "translate {cenx},{ceny} circle 0,0 {outdia},0" -morphology Distance Euclidean:4,1000\
  -fill  "rgba( 0, 255,255 , {inal:0.1f} )"  -stroke  none -draw "translate {cenx},{ceny} circle 0,0 {india},0"  -morphology Distance Euclidean:4,500 \
  -blur 0x{blur} {basename}_{namenum}.gif'''

sys.stderr.write("Starting imagegen .")
for InAlpha,OutAlpha,NameNumber in  zip(InnerAlphaList,OuterAlphaList,NameNumberList):
    FormattedCommand = BaseCommand.format(
        w = CanvasW, h = CanvasH,
        cenx = CenterX, ceny = CenterY,
        india = InnerDia, outdia = OuterDia,
        blur = BlurLevel,
        inal = InAlpha/100.0, outal = OutAlpha/100.0,
        basename = BaseNameString,
        namenum = NameNumber
    )
    sys.stderr.write(".")
    # sys.stderr.write("{}\n".format(FormattedCommand))

    ProcString = subprocess.check_output(FormattedCommand, stderr=subprocess.STDOUT,shell=True) 
    if ProcString:
        sys.stderr.write(ProcString)
sys.stderr.write(" Done.\n")




""" BASE COMMANDS:
 # inner circle:
 convert -size 400x300 xc:black -fill  "rgba( 0, 255,255 , 1 )" -stroke  none -draw "translate 200,150 circle 0,0 75,0" -blur 0x8 -morphology Distance Euclidean:4,1000  blur_circle100.gif

 #outer circle
 convert -size 400x300 xc:black -fill  "rgba( 0, 255,255 , .5 )" -stroke  none -draw "translate 200,150 circle 0,0 150,0"  -morphology Distance Euclidean:4,500  -blur 0x6 blur_circle100.gif

 #both circles
 convert -size 400x300 xc:black -fill  "rgba( 0, 255,255 , .5 )" -stroke  none -draw "translate 200,150 circle 0,0 150,0"  -morphology Distance Euclidean:4,500 \
  -fill  "rgba( 0, 255,255 , 1 )" -stroke  none -draw "translate 200,150 circle 0,0 75,0" -morphology Distance Euclidean:4,1000\
  -blur 0x8 blur_circle100.gif
"""