internal/

Package color implements the PDF color spaces (ISO 32000-2 8.6) the engine needs: the device spaces (Gray/RGB/CMYK, matched byte for byte to the oracle's ICC-backed conversions; see convert.go), CalGray/CalRGB (approximated by their device analogs), ICCBased (mapped to the device space with the same component count), Indexed, and Separation/DeviceN with their tint transforms (internal/function).

Package content tokenizes and interprets PDF content streams (ISO 32000-2 8–9), driving a device.Device: path construction and painting, graphics-state management (q/Q/cm, the ExtGState subset below), clipping (W/W*), color operators, form XObject recursion, image XObjects and inline images (decoded by internal/imaging), text objects (fonts via internal/font), shadings and patterns (internal/shading), and transparency — groups, soft masks, and blend modes.

Package cos implements the COS layer of a PDF document: the lexer, the object model (null, boolean, integer, real, string, name, array, dictionary, stream, and indirect reference), classic and stream cross-reference parsing with /Prev chains and hybrid files, object streams, a repair scan for files whose cross-reference data is broken or inconsistent, an indirect-reference resolver with a cycle guard, and text-string decoding.

Package crypt implements the PDF standard security handler (ISO 32000-2 7.6): revisions 2-4 (RC4 and AESV2) and 5-6 (AESV3).

Package device defines the seam between the content-stream interpreter (internal/content) and its consumers: the raster device (internal/render) and the structured-text device (internal/stext).

Package doc implements document-level PDF semantics on top of the COS layer: the page tree (flattened at open into the page list PageCount and Page answer from), encryption setup, page geometry (the effective box and rotation, and the top-left/y-down space derived from them), destinations (explicit arrays and named, via the old-style /Dests dictionary and the /Names name tree), the document outline, link annotations, and page labels.

Package filter implements the non-image PDF stream filters (FlateDecode, LZWDecode, ASCIIHexDecode, ASCII85Decode, and RunLengthDecode), the PNG and TIFF predictor transforms, and bounded chain application.

Package font implements PDF font semantics (ISO 32000-2 9.5–9.10): font-dictionary and descriptor parsing, embedded font programs, encodings, width resolution, and the deterministic substitution of non-embedded fonts from the bundled data (internal/font/data).

Package function implements PDF functions (ISO 32000-2 7.10): sampled (type 0), exponential interpolation (type 2), stitching (type 3), and PostScript calculator (type 4) functions.

Package gfx holds the shared geometry types the engine's graphics pipeline is built on: points, rectangles, quads, an affine matrix, paths, and stroke parameters.

Package imaging decodes PDF image XObjects and inline images (ISO 32000-2 8.9) into the two raster forms internal/render consumes: straight-alpha RGBA pixels for ordinary images, and a one-byte-per-pixel coverage plane for stencil masks (ImageMask true), which the device tints with the current fill paint.

Package jbig2 一个高性能、零依赖的纯 Go 语言 JBIG2 解码器

Package render is the raster device: the only package that imports github.com/richardwilkes/canvas (canvas/gpu is never imported, keeping the build cgo- and purego-free).

Package shading parses PDF shading dictionaries (ISO 32000-2 8.7.4, types 1-7) into a normalized form the raster device can draw without consulting COS objects again: axial and radial shadings carry a sampled color ramp, function-based shadings carry their domain, matrix, and a color-evaluation closure, and the mesh types (4-7) are tessellated at parse time into flat triangles whose color spread is below one 8-bit step.

Package stext implements the structured-text device.

Package store implements the document-scoped, byte-budgeted resource cache (the fz-store analog): parsed fonts, decoded images, and converted glyph paths register here with byte-size estimates, and least-recently-used entries evict when a New(maxCacheSize) budget would be exceeded.

Package testrand holds the splitmix64 generator the SIMD equivalence tests and benchmarks share.

Package testsupport loads the committed golden files (testfiles/goldens/<name>/truth.json plus rendered PNGs, produced from testfiles/corpus by the oracle module's regen.sh) and provides the comparison helpers the parity tests use.

Package type1 parses Adobe Type 1 font programs (the FontFile stream of a PDF font dictionary): the PFA/PFB container, eexec decryption, the built-in /Encoding, /FontMatrix and /FontBBox from the clear-text portion, and the /Subrs and /CharStrings charstrings (decrypted with r=4330 and their lenIV bytes stripped) from the private portion.

Package vecmath holds the arithmetic helpers shared by this module's goexperiment.simd vector kernels.