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ColorBook Colouring App for iOS

Tap-to-fill colouring on detailed line art, powered by a hand-written scanline flood fill.

iOSSwiftObjective-CCore Graphics
ColorBook Colouring App for iOS

The Problem

Detailed line art has thousands of small regions. A simple recursive fill is slow on full-screen images and can crash on large areas.

What We Built

Scanline flood fill. Rows are filled in one pass and neighbours go onto a linked-list stack, so big areas never overflow.

Tolerance. Anti-aliased line edges fill cleanly.

Tap mapping. The tap is mapped from the zoomable view to the bitmap pixel.

Palette. Preset colours plus a picker for custom colours.

A Note on the Image

Screens use the app's own line-art pictures and palette; the fill shown is illustrative.

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