View Source Pdf.Reader.Images.PNGLike (ExPDF v1.0.1)

PNG-like image decoding for Pdf.Reader.

Handles PDF Image XObjects with /Filter /FlateDecode and optional /DecodeParms predictor. After Flate inflation (via :zlib) and predictor un-filtering, the result is raw pixel data.

API 

decode(stream_bytes, params) :: {:ok, raw_pixels} | {:error, reason}

stream_bytes is the raw (still compressed) XObject stream body. params is the XObject dictionary (or its /DecodeParms sub-dict) and should contain:

  • "Width" (integer)
  • "Height" (integer)
  • "BitsPerComponent" (integer, default 8)
  • "ColorSpace" (name or nil — used to infer number of color components)
  • "Colors" (integer, default inferred from ColorSpace or 1)
  • "Predictor" (integer, default 1 = no predictor)
  • "Columns" (integer, default = Width)

Spec reference

PDF 1.7 § 7.4.4.4 (FlateDecode filter), § 7.4.4.3 (PNG predictor). Delegates to Pdf.Reader.Filter.Flate.decode/2 for the combined inflate + predictor step — the Flate filter implementation already handles PNG predictors 10–15 per batch 2.

Summary

Functions

decode(stream_bytes, params)

Decodes a FlateDecode-encoded image stream to raw pixel data.

Functions

Link to this function

decode(stream_bytes, params)

View Source 
@spec decode(binary(), map()) :: {:ok, binary()} | {:error, term()}

Decodes a FlateDecode-encoded image stream to raw pixel data.

Builds a DecodeParms map from the XObject dict and delegates to Pdf.Reader.Filter.Flate.decode/2, which handles both inflation and PNG predictor un-filtering.

Returns {:ok, raw_pixel_bytes} or {:error, reason}.