Send a Morse code message as an image people can decode

Anyone with a Morse chart can decode a message from an image, as long as three things are plain to see: which marks are dits and which are dahs, where each letter ends, and where each word ends. A picture holds that spacing exactly, which is its great advantage over Morse typed into a message, where fonts, line breaks and automatic punctuation can blur it. Make the dahs clearly longer than the dits, leave a visible gap between letters and a wider gap or a slash between words, and the image will read.

Why a picture of the tape can be decoded

Morse started out on paper. The first telegraph receivers, called registers, marked the dots and dashes on a moving paper tape, and the message was read from the marks. Operators soon learned to read the clicks by ear instead, and the sounder replaced the register on most lines, but a tape works the same way it always did. Morse code on paper tape: how telegraph registers printed it tells that story.

A tape lays the timing of a message out in space. A short mark is a dit and a long mark is a dah. A short space separates the parts of a letter, a larger one separates letters, and a larger one still separates words. Drawn to the timing, the picture keeps the same proportions as the sound: a dah three times as long as a dit, a letter gap three units, a word gap seven. The eye catches those breaks without counting, which is why a neat tape is often easier to read than a line of typed symbols.

Typed Morse has none of that protection. A messaging app may wrap a line in the middle of a letter, a font may make a period almost invisible, and some apps turn two hyphens into one long dash as you type. A picture cannot be reflowed or corrected on the way.

Make the marks and the gaps unmistakable

Whatever you use to make the image, the same rules make it decodable:

• Short dits, long dahs. Draw a dah at least three times the length of a dit. A short dah is easily read as a dit, and the letter changes.
• A clear gap between letters. This is the gap that matters most. AN is .- -.; close the gap and it reads as .--., which is P.
• A wider gap, or a slash, between words. When Morse is written as text, the convention is one space between letters and a slash between words. HI THERE is .... .. / - .... . .-. ..
• Break lines only between words. A line break inside a letter splits it in two, and one inside a word looks like a word gap.
• Big and high contrast. Dark marks on a light background, large enough that a dit survives when the image is shrunk to a preview. Some messaging apps compress pictures, and fine dots are the first thing to go.
• No decoration among the marks. Hearts, stars and dividers between letters can be taken for dits and dahs. Keep them outside the code, or leave them out.

For the full notation, with what to do about figures and punctuation, see How to write Morse code in text: dots, dashes, spaces and slashes.

Three ways to make the image

With a pen and paper. Write the message with a felt-tip pen, dits as firm round dots and dahs as bars three dits long, leaving a finger’s width between letters and at least twice that between words. Photograph it straight on, in daylight, with no shadow across the page. A handwritten message has a warmth a typed one lacks, and it is the easiest to check: you can see every gap.

Typed, then a screenshot. Type the Morse in a notes app in a monospaced font, so every dot and hyphen takes the same width and the spaces line up. Make the text large. If the app turns two hyphens into a long dash, undo it and switch off that substitution before you go on. Then press Shift-Command-4 and drag across the text: by default macOS saves the screenshot to your desktop as a PNG file. The screenshot freezes the spacing exactly as you see it, so check the text before you capture it.

From a Morse tape. Dot & Dash prints every message its machine sends on a paper tape, and you can share that tape as a PNG image. Type a message in Write, or key one on the machine yourself, then share the tape as an image. Each letter is printed under its marks, so the image carries its own answer: good for a keepsake or a lesson, not for a puzzle. The image is made on your Mac, carries the name Dot & Dash and its web address, and goes only where you send it. After the 24-hour trial Write needs a license, but the machine and sharing its tape as an image stay free.

Help the person decoding it

A clear image is half the job. The other half is making sure the reader knows how to start.

1. Say it is Morse code. A strip of dots and dashes can pass for a pattern, a barcode or a doodle.
2. Say which way to read it. Left to right, line by line, with gaps or slashes between words.
3. Point them to a chart, or teach one trick. Someone with a chart beside them can decode any message slowly; someone who knows the Morse tree can do it faster. How to decode Morse code by hand, step by step is a good link to send along.
4. For a puzzle, give a hint of the size. “Two words, nine letters” turns a wall of marks into a problem with edges.
5. Send it at full quality. If your messaging app offers to send a photo as a file or at full resolution, use it, so the dits stay sharp.

Then add a description for people who use a screen reader, which cannot read marks in a picture. “An image of a message in Morse code” lets everyone know what is there. If the message is not a secret, add the Morse as text, in dots and dashes, or the words it spells.

Questions

Can anyone decode Morse code from a picture?

Yes, with a chart and some patience, as long as the dits and dahs differ clearly in length and the gaps between letters and words are easy to see.

Is an image better than typed Morse?

For keeping the spacing, yes: a picture cannot be reflowed, autocorrected or merged into long dashes. Typed Morse is better when the reader wants to copy it and paste it somewhere to translate it.

How do I show the gap between words?

Leave a gap clearly wider than the one between letters, or use a slash, which is the usual mark when Morse is written as text.

How do I turn a Morse image into a puzzle?

Leave the letters off, give a hint of the size, such as “two words, nine letters”, and keep the answer out of the file name and the message you send with it.