Question

I can’t seem to control font size, background and fill.

command 1:

convert             \
   testimage.jpg    \
   label:'Days: 0'  \
  -background Black \
  -fill White       \
  -pointsize 1      \
  -gravity center   \
  -append           \
   days_1.jpg

image:

command 2:

convert             \
   testimage.jpg    \
   label:'Days: 0'  \
  -background White \
  -fill Black       \
  -pointsize 48     \
  -gravity center   \
  -append           \
   days_2.jpg

Answer 1

You didn’t do it right 🙂

You seem to misunderstand the meaning of -label.

See what the official docu has to say about -label:

A label is not drawn on the image, but is embedded in the image datastream via Label tag or similar mechanism. If you want the label to be visible on the image itself, use the -draw option…

Try this command:

convert                               \
   https://i.stack.imgur.com/FoTPN.jpg \
  -pointsize 48                       \
  -fill green                         \
  -gravity center                     \
  -draw "text 100,-200 'Day: 0'"      \
   so-12359743-labelled.png

and you should get this result:

Remember these rules when using -draw:

You can set the primitive color, font, and font bounding box color with -fill, -font, and -box respectively. Options are processed in command line order so be sure to use these options before the -draw option.

(my emphasis)

Alternatively to -draw you can also use -annotate to put text into an image. (However, -annotate uses a slightly different syntax, which you can easily read up about.)

---

Update

Why didn’t you take my hint about the order of the options?!?

Try this command:

convert                               \
   https://i.stack.imgur.com/h2Exm.jpg \
  -background White                   \
  -fill Black                         \
  -pointsize 48                       \
  -gravity center                     \
   label:'Days: 0'                    \
  -append                             \
   days_2.jpg

and you’ll get:

Remember, your -append does concatenate 2 different images:

1. The first one is your original input image.
2. The second one is freshly created with -background ... -fill ... -pointsize ... -label ....

Concatenation with -append does not support -gravity center. This option would only make sense if you had also defined a canvas size for your second picture with -size, but you haven’t.

In the absence of a pre-defined canvas size, the -label operation will auto-create one that is just big enough to hold the text string. You can verify this behavior with this command:

convert                               \
   https://i.stack.imgur.com/h2Exm.jpg \
  -background White                   \
  -fill Black                         \
  -pointsize 48                       \
  -gravity center                     \
   label:'abcdefghijklmnopqrstuvwxyz' \
  -append                             \
   days_3.jpg

Your attempt to use -gravity center led me to believe you wanted the text to appear somewhere in the middle of the original input image. Hence my pointing to -draw and -annotate.