Do the lines in a dot-to-dot ever cross?

No. The dots follow the outline in order, and the built-in pictures are checked so that the closed line through all the dots does not cross itself.

Can I make a dot-to-dot with skip counting?

Yes. Choose "Count by 2", "Count by 5" or "Count by 10" under "Numbers"; the dots are then labelled 2, 4, 6…, 5, 10, 15… or 10, 20, 30…

Where does the child start?

At the dot marked with a star, which is the highest point of the outline. The last dot is joined back to the star to close the picture.

Is there an answer sheet?

Yes. With "Add an answer page" switched on, the second page shows the finished outline with the numbers in light grey.

Dot-to-Dot Puzzle Maker

Turn a picture or a built-in shape into a numbered connect-the-dots puzzle to print, with the finished outline as the answer

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Makes a numbered connect-the-dots sheet from one of 20 built-in pictures or from the outline of a photo or drawing, with an answer page showing the finished outline. It is for parents and teachers who want a counting activity ready to print in a minute.

How to use

Under "Picture", keep "Built-in picture" and pick one, or choose "My photo or drawing" and add a picture; the red line shows the outline that was found.
Set "Number of dots" between 10 and 150, and choose "Numbers": 1, 2, 3… or count by 2, 5 or 10.
Choose "Number size" and "Dot size"; for young children, switch on "Show a faint guide line".
Press "Save as PDF", "Print" or "Save page 1 as PNG". With "Add an answer page", page 2 shows the finished outline.

How it works

The outline of the main object is traced pixel by pixel around its edge (Moore-neighbour tracing), simplified with the Ramer–Douglas–Peucker method so corners become dots, and then evened out to exactly the number of dots chosen.
The dots are numbered clockwise along the outline from the top, so the lines a child draws never cross. Each number is placed outside the shape where it does not touch another number, a dot or a line.
For a photo, the picture is reduced to 480 pixels on its long side, split into object and background by brightness (Otsu's method), and only the largest object with its holes filled is used. Inner details of a photo are not turned into dots.
The chosen settings are saved in this browser; photos are not stored.

How many dots for a dot-to-dot by age

As a rough guide, 10 to 20 dots suit children who are learning to count to 20, 30 to 50 dots suit children who count confidently, and 60 to 150 dots make a longer puzzle for older children. Counting by 2, 5 or 10 turns the same picture into practice for skip counting: with 30 dots and "Count by 5" the numbers run from 5 to 150.

Fewer dots make a simpler shape. If the picture is hard to recognise, add dots; if the numbers crowd together, use fewer dots or smaller numbers.

Making a dot-to-dot from a photo

A photo works best when one object stands on a plain, contrasting background and does not touch the edges of the picture, such as a toy on a white table or a drawing on paper. If the red outline takes in part of the background, move "Brightness cut-off" or set "The object is" to darker or lighter than the background.

Questions and answers

Do the lines in a dot-to-dot ever cross?: No. The dots follow the outline in order, and the built-in pictures are checked so that the closed line through all the dots does not cross itself.
Can I make a dot-to-dot with skip counting?: Yes. Choose "Count by 2", "Count by 5" or "Count by 10" under "Numbers"; the dots are then labelled 2, 4, 6…, 5, 10, 15… or 10, 20, 30…
Where does the child start?: At the dot marked with a star, which is the highest point of the outline. The last dot is joined back to the star to close the picture.
Is there an answer sheet?: Yes. With "Add an answer page" switched on, the second page shows the finished outline with the numbers in light grey.