Hints attempt to correct this by equalizing the weights of stems, preventing parts of glyphs disappearing, and generally maintaining aesthetic appearance and legibility down to as low a resolution as is possible. Introduction Hinting is at the heart of TrueType. Instead, they linked a relatively simple rasterizer to a new interpreted programming language. Each glyph in the font contains its own little hint program, with which the control points of the outlines can be manipulated just prior to rasterization in any way the hint programmer desires . In practice, this means that the outline is carefully distorted by each glyph's hinting instructions to surround only those pixels that produce the desired bitmap image.
Instructions take the form of single-byte codes.
Also unlike PostScript, there are no actual drawing instructions - only instructions that move existing control points. Note that TrueType hint editors, such as TypeMan , hide the stack-based nature of the language from the hint programmer, letting one edit each instruction alongside its arguments. Glyph Scaling Before any hints are applied, the glyph is scaled with respect to the current ppem . All the glyph's coordinates are now measured in fractional pixels, rather than integral font design units. TrueType's power stems partly from the independence of these vectors, and the ability to set them diagonally.