AI Coloring Books

An AI coloring book is a set of machine-generated outline pages, ordered, bound, and printed as one thing. Making one takes four steps: pick 12 to 24 photos with one clear subject each, convert them, put them in order, and export a single PDF. The part that decides whether the result feels like a book has nothing to do with the AI — it is page count, paper, and binding, and almost nobody explains those. Measured on our own export code: a 24-page book comes out at 251 KB and takes 0.26 seconds to assemble, at a flat 10.4 KB per page. Every number below is measured or read from our source, not estimated.

The short answer

Open the Coloring Book Maker, drop in the photos, rearrange, export. The rest of this page is about the decisions that come after that click.

Making one: four steps

1. Gather the photos. One clear subject per photo — a pet, a toy, a flower, a car. Busy group shots and low-contrast indoor pictures produce a thicket of small lines.
2. Convert and check each one. Every page can be tuned on its own: Edge Detail, Smoothness, Line Width, and a Dark background toggle for photos shot against a dark scene. Which settings suit which photo type, with measured ink coverage, is on Turn Photo Into Line Drawing.
3. Put them in order. Drag a page by its handle, or use the arrows. If you are printing double-sided, remember that page 2 lands on the back of page 1 — the order you set is the order that prints.
4. Add a cover and export. The optional cover is rasterized at 1200 × 1553 pixels with your title, which lands at about 162 DPI on the page. Then build the PDF.

First time converting a photo? The walkthrough is on Convert a Picture Into a Drawing.

Measured: what the PDF actually weighs

We ran our real PDF writer — the same code the browser runs — over 32 distinct pages generated from our test photo at the 1400 × 1050 pixel cap, and built books of 1, 4, 8, 12, 16, 24 and 32 pages. Sizes are of the finished file; build time is the median of three runs on a Windows machine with an AMD EPYC 9754 running Node 22 (your device will differ, the shape of the curve will not).

Three things fall out of that table.

• The cost per page is flat, about 10.4 KB. There is no fixed overhead that shrinks as the book grows, so a 32-page book really is 32 times a one-page book. Each page is written as its own compressed grayscale image, and pages are compressed independently — one busy picture does not make the others cheaper or more expensive.
• Compression is doing enormous work: about 144×. A full 1400 × 1050 page is 1,470,000 bytes of grayscale samples — one byte per pixel, no colour channels — and deflate brings a mostly-white line drawing down to roughly 10 KB. Without it, that same 32-page book would be 44.9 MB, which is over most email attachment limits and past the upload cap of a good many online print services.
• Assembly is not the bottleneck; conversion is. Writing a 24-page PDF takes 263 ms. Converting the 24 photos beforehand took 4.30 s for 32 of them, which is about 134 ms per photo at the pixel cap — so the book is essentially as fast as the sum of its pictures.

One honest caveat on the file size: the writer only uses compression if the compressed version is actually smaller, and falls back to raw samples if the browser does not implement CompressionStream at all — older Safari in particular. On that fallback path the numbers in the last column are what you get, and a 24-page book is 33.7 MB. It still prints, it is just awkward to move around.

Page count is a binding decision, not an AI decision

This is the step people skip, and it is the one that decides whether you end up with a book or a loose stack. Pick the binding first, then let it set the page count:

So the practical rule: if you want a stapled booklet, land on 16 or 24 pages. If you are punching and binding with a comb, any number you like. Adding the optional cover page makes the count one higher, so if you are chasing a multiple of 4, turn the cover on and export 15 pictures, or leave it off and export 16.

Printing double-sided halves the sheet count — 24 pages is 12 sheets — which is what you want for a stapled booklet. It also means a drawing sits directly behind another drawing, so thin paper shows ghosting through the sheet. For a double-sided book use 90–120 gsm at least; for single-sided, ordinary 20 lb / 75 gsm copier paper is fine with crayons and coloured pencils.

How sharp the lines land, and why it matters more in a book

Every page is US Letter, 612 × 792 points, with a 40 point (14 mm) margin all round and the drawing centred inside it, scaled to fit and never cropped. Source pixels are capped at 1400 on the long side, so the effective resolution is about 190 DPI for square and landscape photos and 142 DPI for portrait ones, and a single source pixel prints at 0.13–0.18 mm. The full derivation, and what to do if you print on A4, is on Coloring Page Generator; the cover page is rasterized a little lower, at about 162 DPI.

Why this bites harder in a book than on a single sheet: a lone page gets judged on its own, while twenty-four pages get compared with each other. If three of your photos were shot in dim light and produce fine broken outlines while the rest are clean, the book reads as inconsistent — and the fix is per page, not per book. Raise Line Width to 2 or 3 on the weak pages before you export; it costs nothing in file size and it is the difference between an outline a crayon can follow and one it cannot.

What makes a good book, and what makes a bad one

• Good: one subject, plain background, even light. A pet on a lawn, a toy on a table, a single flower. These trace cleanly at default settings.
• Good: a theme. "Our street", "the zoo trip", "things in the garden". A book with a theme is the one that gets finished rather than abandoned on page four.
• Bad: twenty photos of the same thing. Variety is the whole point of a book; four near-identical pages of one dog reads as filler.
• Bad: busy backgrounds and heavy fabric patterns. They convert into dense small lines that are tiring to colour and look muddy at 142 DPI. Crop in before you add them.
• Bad: leaving the order as it happened to import. Put an easy, appealing page first and a strong one last. Children quit at the hardest page.

Printing it: four settings worth checking

• Scale. Choose actual size or 100% on Letter paper. On A4 choose fit to page, which shrinks it about 3%.
• Colour. Set the driver to black and white or grayscale. The pages contain no colour at all, and this stops the printer burning ink on a colour profile.
• Double-sided. On for a stapled booklet, off if you are using thin paper or want the drawings cut out and hung up afterwards.
• Draft or eco mode. Print one page first. On some printers it lightens thin outlines enough that the line disappears.

Why making books locally matters more than making pages locally

A single uploaded photo is one image. A coloring book made from a class trip is thirty photographs of other people's children, and that is the kind of collection that triggers consent letters, vendor reviews, and a conversation with the school office. Here every conversion and the PDF itself happen in your own browser tab; nothing is transmitted, and there is no copy anywhere else to delete afterwards. There is a structural reason behind that promise rather than just a policy: the whole site is served by one Worker that maps a URL to a page and returns it, with no database, no object storage, and no code path that accepts an upload. The detail is in the Privacy Policy, and the reasoning is spelled out on AI Coloring Pages.

Three other things you can make from the same photos

Outlines are only one output. Picture to Color by Number reduces a photo to a small numbered palette, which suits children who would rather be told which colour goes where. The Name Coloring Page Generator puts a child's name in big outlined letters — useful as the cover sheet for a book made for one child. And if you only need a single sheet, the generator does it without building a PDF at all.

Questions

How many pages can one book have? There is no cap in the tool. The practical ceiling is your patience and your binding — 24 pages is a substantial book for a child, and 32 is a lot of colouring.

Can I reorder pages after exporting? Not inside the PDF. Reorder the list and build again; at 10.4 KB per page and a quarter of a second of assembly, rebuilding is cheaper than fixing it.

Does the file size grow if my photos are huge? No. Every photo is rescaled so its long side is at most 1400 pixels before tracing, so a 12 MP camera file and a 2 MP one produce the same page size.

Will the PDF open anywhere? Yes. Every page is written as an image rather than as text and layout, so there are no fonts to substitute and nothing to reflow. It looks identical on your machine, on the school computer, and at the print shop.

Can I send it to a print shop? Yes — at 251 KB for 24 pages it is well inside any upload limit. Ask for the pages to be printed at actual size, not scaled to fit a house template.

Is "AI" doing the drawing? The outlines are produced by a deterministic edge-detection pipeline, not a generative model, which is why it can run on your device instead of a server. There is nothing to sign up for and no queue to wait in.

Do I own what I make? You own the photos you started from, and we keep no copy of them or of the book. Nothing is watermarked.