How can I draw mirrored text onto an image using ImageMagick? - ruby

Question

I'm using ImageMagick (through the MiniMagick Ruby Gem) to crop an image, I also add an annotation to the top of it, but I want it to be mirrored.
I know ImageMagick has a 'flop' command which mirrors an image, but I'm not sure how to generate the text, flop it and compose it onto my image.
Here is how I currently draw the text (non mirrored). This code uses MiniMagick, but it translates pretty directly to actual ImageMagick commands.
image.combine_options do |c|
c.resize "1000"
c.font Rails.root.join('app/assets/fonts/Menlo.ttc').to_s
c.fill '#888888'
c.pointsize '16'
c.draw "text 0,0 '#{annotation}'"
end
How can I modify or replace this to draw mirrored text?

Answer 1

First, you should, for your Minimagick code, do yourself the 'translate pretty directly to actual ImageMagick commands', if you really are interested to get the biggest possible input. Not everyone here wants to learn Minimagick first, before he can chime in with his suggestions.
Second, you didn't tell which way you want your text mirrored: Left-right? Upside-down? Combined?
Third, try to replace these 2 lines
c.pointsize '16'
c.draw "text 0,0 '#{annotation}'"
by these 3 lines
c.pointsize '16'
c.draw "text 0,0 '#{annotation}'"
c.flop
or by these 3 lines
c.pointsize '16'
c.draw "text 0,0 '#{annotation}'"
c.flip
or by these 4 lines
c.pointsize '16'
c.draw "text 0,0 '#{annotation}'"
c.flip
c.flop

Answer 2

Now that Nathan admits he's 'familiar' with -flip and -flop for images only, let's show him how one can use that to nevertheless get flipped and flopped text annotations onto unchanged images.
See these two examples:
Left with with normal text, right with mirrored text (left-right mirrored - Nathan didn't respond to the question if he wanted this, or if he wanted top-bottom mirroring).
How was it done?
The left image's annotation was done with the following command:
convert \
logo: \
-fill white \
-undercolor '#00000080' \
\( \
-gravity west \
-pointsize 32 \
-annotate +0+40 \
" Dude! Listen, don't argue... " \
\) \
-scale 310x \
normal.png
So this result is the basis for the next step. In the next step we will modify this command to create a mirrored text annotation. But, since we cannot write mirrored text directly, we use one of the many tricks up in our sleeves:
Mirror the image first (first -flop).
Write normal text on mirrored image.
Mirror the resulting image one more time (second -flop). This way...
...main image is back to normal,
...annotation text is mirrored now.
And this leads to the left image's annotation command:
convert \
logo: \
-flop \
-fill white \
-undercolor '#00000080' \
\( \
-gravity east \
-pointsize 32 \
-annotate +0+40 \
" Dude! Listen, don't argue... " \
\) \
-flop \
-scale 310x \
mirrored.png
Easy, eh?
(Just notice how we also had to change the gravity from west to east so that the text appears on the same spot...)
It's Nathan's own job now to translate this algorithm into Minimagick's language.