How to draw perfect circle?

[BParkoff]

Hi,

I was in glyph panel. I clicked the "Add Ellipse" icon. I drew the perfect circle on the grid from (top, left): 500, 100 to (bottom, right): 100, 500. The diameter is 400 units.

I clicked "Test Desktop Font (TTF/OTF)" from Font menu.

I changed the font size from 10 points through 48 points to test the perfect circle.

All the sides (top, top-right, right, bottom-right, bottom, bottom-left, left, and top-left) of circle should have identical perfect curve.

The edge of left shows two pixels and other edge of right shows four pixels. Both edges of top and bottom have identical two pixels.

How can I make identical perfect sides of circle when the font sizze is changed from 10 points through 48 points?

Kindly,
Bryan Parkoff

[Bhikkhu Pesala]

This sounds like a rounding error. Circles are never going to be perfect on a pixelated grid.

See Perfect Circle Made Out Of Quadratic Bezier Curves.

[BParkoff]

Hi,

You may be right that FontCreator has a rounding error. I will like to share my findings how the circles are going to be perfect on a pixelated grid.

I downloaded the font with TTF format file from the internet. I opened the font with TTF format file into FontCreator.

I was in glyph panel. I saw the perfect circle.

I clicked "Test Desktop Font (TTF/OTF)" from Font menu.

I changed the font size from 10 points through 48 points to test the perfect circle.

All the sides (top, top-right, right, bottom-right, bottom, bottom-left, left, and top-left) of circle now have identical perfect curve.

I closed "Test Desktop Font (TTF/OTF)" dialog. I was on the glyph panel. I clicked on the circle. I was on transform panel. I clicked Size tab. I changed from 180 to 190 on both width and height. I clicked Apply button.

I clicked "Test Desktop Font (TTF/OTF)" from Font menu.

I changed the font size from 10 points through 48 points to test the perfect circle.

All the sides (top, top-right, right, bottom-right, bottom, bottom-left, left, and top-left) of circle should have identical perfect curve. It is still imperfect circle.

I closed "Test Desktop Font (TTF/OTF)" dialog. I was on the glyph panel. I clicked on the circle. I was on transform panel. I restored the original values of width and height from 190 to 180. I clicked Apply button.

I clicked "Test Desktop Font (TTF/OTF)" from Font menu.

I changed the font size from 10 points through 48 points to test the perfect circle.

The result is still the same. It is still imperfect circle.

I closed "Test Desktop Font (TTF/OTF)" dialog. I was on the glyph panel. I clicked "Undo" from Edit menu two times. The original value on both width and height were restored back to the factory default from opened font with TTF format file.

I clicked "Test Desktop Font (TTF/OTF)" from Font menu.

I changed the font size from 10 points through 48 points to test the perfect circle.

All the sides (top, top-right, right, bottom-right, bottom, bottom-left, left, and top-left) of circle now have identical perfect curve. It is still perfect circle!

You clearly stated that FontCreator is never going to make perfect circle due to the rounding error because it uses integer format instead of floating format. Is this correct?

Is there special Font Designer professional software available? The professional software can make perfect circle like I downloaded the font with TTF format file earlier and I mentioned my finding above.

Kindly,
Bryan Parkoff