Need help with making a polygon look totally flat

Jonathan Lynch jonathandlynch at
Fri Apr 18 14:44:45 EDT 2014

Hello everyone,

I am creating a coloring book application for work, to be marketed to kids.
Of course, this means having to create my own basic painting tools because
the standard painting tools are not available for IOS.

Creating a freehand line polygon (9 pixels thick) and having it draw new
segments in sync with mouse movements is a pretty easy way to simulate a
brush. It is also easy to merge this polygon down onto the underlying image
upon releasing the mouse button.

However, this polygon does not have a single color. Instead, there is a
very slight light edge and dark edge. I assume this is a standard part of
polygons in order to make them more visually appealing. Unfortunately,
these edges also merge down into the underlying image.

This doesn’t look horrible, but it messes up subsequent flood fill (paint
bucket) operations.

Is it possible to alter the settings of a polygon so that it is purely
flat, with not even a slight light or dark edge? I have experimented with
coloroverlay, antialiasing, and all ink settings, but to no avail. I could
have the polygon merge with a pure white image off-screen, work with the
imagedata and alphadata to remove all pixels that are not of the correct
color, then merge this new image with the main image – but that sounds like
a really slow and difficult kludge. Surely there is a way to just totally
flatten the look of a polygon?

And speaking of flood full – ugh, scripting that was a nightmare. I really
wish we could use the built-in flood fill operations in IOS.

Thank you greatly for any suggestions,

Do all things with love

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