How to resize a PNG file from the command line

Save a python script like this:

#!/usr/bin/python
from PIL import Image, ImageFont, ImageDraw
import sys

im = Image.new('CMYK', (1000,1000), (0, 0, 0, 255))

f = ImageFont.load_default()
d = ImageDraw.Draw(im)
d.text((500, 500), sys.argv[1], font = f, fill = (0, 0, 0, 0))
del d

im.save(sys.argv[2])

Dependencies are python and the python imaging library. Then you can create your images with this command:

python cmyktext.py "Josh test" Jtest.pdf

Don't forget that cmyk is subtractive, so (0,0,0,0) is actually white. It is of course also possible to use any font you like, as documented here.

I found an inelegant way to do that using orion's proposal. Assuming $svg_file_name is a variable containing file path to an SVG image.

First we need image width and height

width=$(exiftool -ImageWidth $svg_file_name | sed "s/.*: //;s/pt//g")
height=$(exiftool -ImageHeight $svg_file_name | sed "s/.*: //;s/pt//g")

PlantUML produces the diagram as a single group (tag <g>), let's place rectangle of canvas size over that group

sed -i "s|</g>|</g><polygon fill=\"#FFFFFF\" points=\"0,0,0,$height,$width,$height,$width,0\" style=\"stroke: #000000; stroke-width: 1.0;\"/>|" $svg_file_name

Now open image with inkscape, select all and clip the group with the rectangle

inkscape --verb=EditSelectAll --verb=ObjectSetClipPath --verb=FileSave --verb=FileClose $svg_file_name

With the latest Inkscape one needs to quit Inkscape instead of closing the file

inkscape --verb=EditSelectAll --verb=ObjectSetClipPath --verb=FileSave --verb=FileQuit $svg_file_name