Split a Bash script with ImageMagick instructions into smaller pieces? - bash

Question

I have this bash script, feeding drawing information into ImageMagick, which starts like this:
#!/bin/bash
convert -size 2200x2200 xc:white \
-fill '#FFFEFF' -draw 'point 1112,1111' \
-fill '#FFFEFE' -draw 'point 1112,1112' \
-fill '#FFFEFE' -draw 'point 1111,1112' \
-fill '#FFFEFE' -draw 'point 1110,1112' \
-fill '#FFFEFE' -draw 'point 1110,1111' \
******ON & ON 4.2 MILLION LINES MORE*******
spectrumspiral.png;
My problem is I keep getting warnings about argument list too long, terminal says 'Killed', warning about 'fork: cannot allocate memory etc.
I've tried adjusting ulimit -s to a much higher value to no avail. Really want to make this image. Any idea how I can feed the terminal chunks of this script at a time? Or something to that end.
I've heard xargs can be used for things like this, but I haven't been able to find a specific implementation that fits the nature of this problem.

Answer 1

If you create an image with 4 pixels in it (1 red, 1 white, 1 blue and 1 black), you can tell ImageMagick to output the resulting image as text file as follows:
convert -size 1x1 xc:red xc:white xc:blue xc:black +append -depth 8 -colorspace RGB image.txt
# ImageMagick pixel enumeration: 4,1,255,rgb
0,0: (255,0,0) #FF0000 rgb(255,0,0)
1,0: (255,255,255) #FFFFFF rgb(255,255,255)
2,0: (0,0,255) #0000FF rgb(0,0,255)
3,0: (0,0,0) #000000 rgb(0,0,0)
By the same token, if you feed that text file into ImageMagick, it can recreate the image:
cat image.txt | convert txt:- output.img
So, all we need to do is convert your -fill commands into a text file of the format that ImageMagick likes. So we can do this to yourFile
sed -E 's/.*(#[0-9A-F]+).* ([0-9]+)\,([0-9]+).*/\2,\3:\1/g' yourFile
and we will get something like this:
0,0:#3C4AD8
0,1:#269531
0,2:#CF2C7C
...
...
which we can then pipe into awk to rearrange how ImageMagick likes it:
awk -F: '
BEGIN{print "# ImageMagick pixel enumeration: 2200,2200,255,rgb"}
{
coords=$1;colour=$2
rh="0x" substr(colour,2,2);
gh="0x" substr(colour,4,2);
bh="0x" substr(colour,6,2);
r=strtonum(rh);
g=strtonum(gh);
b=strtonum(bh);
printf "%s: (%d,%d,%d) %s\n",coords,r,g,b,colour;
}'
So, if we put all that together, the following script should be able to create your beloved image into the file spectrumspiral.png:
#!/bin/bash
sed -E 's/.*(#[0-9A-F]+).* ([0-9]+)\,([0-9]+).*/\2,\3:\1/g' yourFile | awk -F: '
BEGIN{print "# ImageMagick pixel enumeration: 2200,2200,255,rgb"}
{
coords=$1;colour=$2
rh="0x" substr(colour,2,2);
gh="0x" substr(colour,4,2);
bh="0x" substr(colour,6,2);
r=strtonum(rh);
g=strtonum(gh);
b=strtonum(bh);
printf "%s: (%d,%d,%d) %s\n",coords,r,g,b,colour;
}' | convert txt:- spectrumspiral.png

Answer 2

Try using the shell's here-document
#!/bin/bash
convert - <<EOS spectrumspiral.png
-size 2200x2200 xc:white
-fill '#FFFEFF' -draw point '1112,1111'
-fill '#FFFEFE' -draw 'point 1112,1112'
-fill '#FFFEFE' -draw 'point 1111,1112'
-fill '#FFFEFE' -draw 'point 1110,1112'
-fill '#FFFEFE' -draw 'point 1110,1111'
# ******ON & ON 4.2 MILLION LINES MORE*****
EOS
My system doesn't have convert so I can test that this works.
Most linux programs (including convert) can accept input from StdIn, which in the cmd-line above is represented by the - char. The - tells the command to expect input, not from file, but as if it was being typed at the keyboard, ie StdIn. The <<EOS .... EOS is the here-doc, and it represents bash 'typing' in all of that text into the commands stdIn input.
You may or may not need all of the quoting, if you already have there, I don't think it will hurt. If this doesn't work as is, use a small sample file of input (like above) and test various scenarios until it creates a file for you.
IHTH