[ft] FreeType Rasterizer/Renderer and Dropouts

[Mike Franklin]

Hello,

I'm experimenting with using FreeType's rasterizer and manually drawing outlines and strokes.  All is going well, but I'm encountering some rendering anomalies that I don't quite understand.  Please see the attached image.

I'm guessing the chosen word for the anomaly illustrated in the image is "dropout", but I'm not sure. 

Can anyone explain this symptom and let me know if there's anything I can do about it?

The code I used to generate the image is part of a much larger project, but here's the general procedure I'm following.

I create a stroker with a radius of 0.5:

FT_Stroker_New(stroker, 0.5 * 64, cap, join, 0);

I create 8 bezier curves to approximate a circle:

FT_Stroker_ConicTo(stroker, &v0, &v1);  // x8

I export the stroker to an outline

FT_Outline outline;

FT_Stroker_Export(stroker, &outline);

Then I render the outline using a raster callback to take advantage of some features of my hardware.

FT_Raster_Params params;
params.flags = FT_RASTER_FLAG_AA | FT_RASTER_FLAG_DIRECT | FT_RASTER_FLAG_CLIP;
params.gray_spans = RasterCallback;

FT_Outline_Render(library, &outline, &params);

I'm using FreeType v2.6.0

Thanks in advance for the help.

Mike