Dumpling Sandwich

Martin Dong, Founder

Vancouver, Canada

“Dad made that.” Martin Dong and his daughters hold up Pencil Sketch creations of their own.

The Pencil Sketch effect: turning a photo into an artistic pencil drawing with color on Android.

2026

Dumpling Sandwich helps people turn photos into full-color sketches for free

In 2012, Martin Dong launched Pencil Sketch, a mobile app that helps people transform photos into pencil sketches, including full-color sketches. Built mainly to reach as many people as possible, and supported with advertising, Pencil Sketch has racked up tens of millions of downloads over its lifetime, with Martin’s entire app portfolio accruing 100 million downloads over time. Today, Martin continues maintaining his apps under the name Dumpling Sandwich (a nod to his Chinese-Canadian story) while working full-time again and exploring what AI might bring.

Coloring outside the lines

By 2012, Martin Dong, who studied image processing and computer vision, had already ticked off the usual boxes:

Master’s degree. Check.

Startup jobs. Check.

But around the same time, a massive technology shift was also unfolding before his very eyes, something he couldn’t ignore. Mobile was taking off, and with it a young mobile operating system by the name of Android was set to make its mark.

“The Google Play Store didn’t exist yet,” Martin elaborated, referring to today’s digital marketplace where Android users can get their apps and digital content from. “It was called Android Market back then.”

Either way, Martin was enthralled. New devices. Bigger screens. New capabilities. What more could he ask for? “I really loved Android back then,” he said.

So, naturally, with his background and training, building for Android was the obvious next box to check.

“Probably more than 10 apps,” he said, counting all the different directions he ended up taking at the time, publishing a new app, learning from his mistakes, then doing it all over again.

But his persistence would eventually pay off when he noticed something in particular on the other side of the proverbial fence: iPhone users, with their App Store, could pick from a bunch of apps that would transform people’s photos into pencil sketches.

And this idea of an image processing app, of course, resonated with a bona fide image processing expert. It was right in his wheelhouse.

All this prompted Martin to go look inside Android Market and see what that side actually had. And while he did in fact stumble upon a few sketch apps, they were limited to only generating black-and-white sketches.

“That’s when I knew how to stand out from the pack,” he said, talking about the missing component: sketches in color.

It was serendipitous. Martin, with his master’s work on how computers interpret images, applied that knowledge to making an app of his own for Android.

So, in June 2012, Pencil Sketch made its debut. It was an app built to help anyone with an Android device turn their photos into sketches, and not just in black-and-white, but also beautiful, full-color sketches.

And it made all the difference. Almost immediately, the app found its audience. “It started to gain traction,” Martin said, reaching “a couple million downloads” early on.

Color sketches, taking something familiar and pushing it further, was what made Pencil Sketch stand out. Martin stands out in his own way as well. He was born and raised in China, later making his home in Canada. So when it came time to name his developer studio, he chose something that felt distinctly him — a Dumpling Sandwich.

Not a real dish, mind you, but something worth having nonetheless. “I come from two different places. I prefer two different kinds of food,” he said, proudly. “I myself am a combination of two cultures.” It was Martin, unfiltered.

A full color sketch effect made with Pencil Sketch

Drawing a line to “free”

Martin’s goal for Pencil Sketch was always about reach first, getting as many people possible to try his app. “I wanted to get as many installs as I could,” he remembered.

That also meant that Pencil Sketch had to be priced with that goal in mind; in other words, free.

And Martin didn’t need to present another master’s thesis to make the case that paid downloads would limit his reach. Even pricing his app at $0.99 (the lowest price available) “rules out probably 90% of mobile users already,” he realized.

But this is exactly the kind of conundrum that the ad-supported business model was made to solve, and why Martin adopted it for Pencil Sketch in the first place. With this model, users get to access his app for free, while advertising funds all his work behind the scenes.

That’s why he baked ads into his app plans all along. “The very first version of the app… it had AdMob in there,” he said, point blank.

He even remembers the “good old days” when “banner ads were the only format around.” But as the ecosystem evolved, rolling out new formats like interstitials, then native ads, and then rewarded ads, AdMob rolled right along with them. “I started to basically only use AdMob,” he said.

Eventually, AdMob brought out additional features like mediation and real-time bidding — where multiple ad sources can compete for an impression, and the ad with the highest yield wins.

“I started to use AdMob mediation… to boost the eCPM,” he said, referring to the effective revenue a developer can earn per thousand impressions.

“98% to 99% of Dumpling Sandwich’s revenue comes from ads.”

A black and white Pencil Sketch portrait created on Android

A blend that keeps working

Ads had given Martin a model that he could stick with for the long haul. So, in 2015, two years after treating Dumpling Sandwich like a side hustle, Martin finally quit his day job to work on his apps full-time.

And Pencil Sketch’s users definitely benefited from his renewed focus. They got more filters, more editing tools, stickers, even drawing features.

Martin benefited too. His audience kept growing, up to tens of millions of downloads for Pencil Sketch, and over 100 million cumulative downloads across his entire app portfolio. Financially, ads were still the backbone of it all: “98% to 99% of Dumpling Sandwich’s revenue comes from ads.”

“It’s definitely life-changing,” he reflected. He talked about meeting other developers, comparing notes, and learning faster. “Every time there was a conference, I was super excited to meet my peers,” he said. “We share some stories, challenges, how we solve them.”

And he also talked about a sense of pride, deservedly so. “I can show [my daughters] what I built and then they feel proud of this, they feel proud of me,” he said. “I even took them to Google’s headquarters once. They loved it.”

Nowadays, Martin’s app business can be found in a kind of maintenance mode, still serving a large audience every day, with Martin making the occasional update, all while he’s gone back into full-time work as an engineer.

When asked about what the future might hold for Dumpling Sandwich, Martin said the approach would still be the same: tap into a large audience, monetize with ads.

And sure enough, Martin is seeing yet another technology shift take place these days, and while he says he doesn’t have a specific app idea yet, he’s paying close attention to how AI is changing what’s possible.

Meanwhile, back at home, he already has a couple of power users (and tough critics) to look after: two daughters who can tap his app’s icon on a phone and say, "Dad made that".

About the Publisher

Martin Dong is the founder of Dumpling Sandwich Software Inc., a mobile app studio best known for a popular app that turns photos into color pencil sketches, appropriately named Pencil Sketch. Martin, who was born and raised in China and is now based out of Canada, dubbed his studio an equally appropriate name, equal parts eastern and western — Dumpling Sandwich.

Martin Dong, founder of Dumpling Sandwich Software Inc., and creator of the Pencil Sketch app