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text-rendering

text shaping and font rendering

HarfBuzz, FreeType

SystemTechniques · 5Primitives · 16 text-rendering Font fallback itemizationgraphics · medium: Split text into runs by script, direction and font coverage; pick fallback fonts per runKnuth plass line breakinggraphics · medium: Optimal paragraph line breaking minimizing total badness with boxes, glue and penaltiesPath rasterization coveragegraphics · medium: Scanline or sparse-strip coverage accumulation with nonzero and even-odd fill and analytic antialiasingText shapinggraphics · medium: Map Unicode to positioned glyphs via OpenType GSUB/GPOS lookups, clusters and complex scriptsUnicode bidi algorithmgraphics · medium: UAX 9: resolve embedding levels and reorder mixed left-to-right and right-to-left textOpentype font parsinggraphics · low: Sfnt tables (cmap, glyf, CFF, hmtx, GSUB, GPOS), variable font axes, safe parsingUnicode text tokenization for searchsearch-sort · low: Turn multilingual text into index terms: segment words (UAX 29 style, CJK bigrams), normalize, case-fold and accent-fold, identically at index and query time.›Unicode line breakinggraphics · low: UAX 14 line break opportunities plus hyphenation hooksBézier curvesgraphics · low: Smooth curves defined by 3-4 control points, evaluated and split with repeated linear interpolation (de Casteljau) and flattened to lines with a closed-form segment count.›Color space conversiongraphics · low: Convert pixels between transfer curves (sRGB, linear light), primaries (sRGB, Display P3, XYZ) and Y'CbCr, using tables for the curve and 3x3 matrices for the rest.›Font hintinggraphics · low: Grid fitting of glyph outlines: TrueType bytecode VM, autohinting, stem darkeningGlyph atlas cachinggraphics · low: Rasterize glyphs on demand into GPU texture atlases keyed by glyph, size and subpixel offsetSigned distance field renderinggraphics · low: Render glyphs and shapes from SDF or MSDF textures for crisp scalingRectangle bin packingoptimization · low: Skyline, guillotine and MaxRects packing for texture and glyph atlasesLRU and CLOCKsystems · low: LRU evicts the least recently used entry via hash map plus linked list; CLOCK approximates it with a reference bit, so hits take no lock.›Dijkstra's algorithmgraphs · low: Single-source shortest paths with non-negative edge weights by settling vertices in order of distance with a priority queue.›Parallel prefix sumsearch-sort · low: Work-efficient scan (Blelloch, decoupled look-back) on CPU SIMD and GPUs; stream compactionText position encodingcompilers · low: Store byte offsets, convert to (line, column) on demand with a line-start table and binary search, and count columns in the unit the peer negotiated.›d-ary heapdata-structures · low: Array heap with d children per node (d = 4 typical): half the binary heap's depth, siblings in one cache line, faster priority queues.›Text normalizationmachine-learning · low: Rewrite messy text into one canonical form for matchers and models, or into spoken words for speech output (and back), keeping a map to the original offsets.›Chroma subsamplingmedia · low: 4:2:0/4:2:2 colour plane downsampling and siting

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