For some Slow Scan TV (SSTV) experiments I want to be able to overlay text on images from the command line or within a script. The Swiss-army-knife of image manipulation is ImageMagick, so I’m using that.
Starting with a a photograph I took a few years ago, I resized it to 320×256 pixels – that’s the Martin-1 SSTV mode frame size.
I can then use the following ImageMagick command to add some text in a shaded box.
convert -fill white -background '#00000080' -gravity North -size 320x40 caption:'G7UVW SSTV' small-electronics.png +swap -gravity north -composite small-electronics-captioned.png
For now it just adds simple static text, but in production it’ll add dynamic data as well as static text, for example, computer load, camera pointing and RF subsystem data.