OUTLINE FONT HOW TO

If the paper design is digitized directly as quadratic splines the major work of describing outlines in the TrueType format is done. This method may not work, however, as the two curves will most likely have different velocities making it necessary to reparameterize the two curves in terms of arc length.Ī better method for determining the error would be to measure the distance for the original curve to the new curve along a perpendicular line as shown in FIGURE 1 below.įIGURE 1 Measuring the error in a curve approximation

In looking at the original curve and the curve intended to approximate it, it might be tempting to measure the error of approximation by looking at the curve value for each of the two parametric equations specifying the two curves at the same value for t. This book can only suggest some approaches that might be taken and warn against some of the pitfalls. All of the available methods have associated pitfalls.

OUTLINE FONT HOW TO

How to measure error?There is more than one way to measure the error involved in curve approximation. The quality obtained with the letter 's' is often a good indicator of the acceptability of that tolerance, asthere are many curves and transition points. In attempting to decide whether the chosen error tolerance is acceptable, it is necessaryto look at the output produced. As a rule of thumb, an error that is less than 1/1000 of the em square will generally meet this guideline. If the possible error in an outline description is less than the error inherent in the most sensitive rendering device expected to be used, none of the attainable accuracy in the typeface design is lost. The tricky parts in this process are determining the degree of accuracy needed and then deciding how to establish whether a given font meets the accuracy guidelines. While a given curve may not be exactly representable in the quadratic spline format, that curve can always be represented as accurately as required.

Once this number is established, conversion becomes merely a matter of finding a set of quadratic curves that describe the original design within the stated tolerance. Here the problem is one of determining an acceptable error or tolerance value. A more complex problem arises when converting from some other format or when digitizing a paper design. For designs developed directly in the TrueType format the curves used define the design exactly.

This section considers some of the issues involved in converting outlines from other outline formats to the quadratic splines supported by the TrueType format.Ī key issue in any outline font design is how closely must the curves used to represent a glyph shape resemble the intended glyph design. Converting Outlines to the TrueType Format

Outline font