View Source Pdf.Reader.Image (ExPDF v1.0.1)

Struct representing an image extracted from a PDF page.

Each struct corresponds to one image XObject referenced by a Do operator in the page's content stream.

Coordinate fields

  • :x, :y — bottom-left translation in user space (CTM e/f components).
  • :width, :height — PIXEL dimensions from the image XObject's /Width and /Height entries (the image's intrinsic resolution). May be nil for an image XObject without those entries (rare).
  • :render_width, :render_height — user-space rendered dimensions derived from the CTM column-vector magnitudes (sqrt(a*a + b*b), sqrt(c*c + d*d)).
  • :ctm — the full 6-float affine matrix {a, b, c, d, e, f} at Do time. Default is the identity matrix {1.0, 0.0, 0.0, 1.0, 0.0, 0.0}.
  • :rotation_radians — :math.atan2(b, a) — angle of the x-axis in page space.

For writer-built PDFs using [pixel_w 0 0 pixel_h x y cm] /Img Do, pixel and rendered dimensions agree and rotation_radians is 0.0. For real-world PDFs that scale or rotate images, the two dimension pairs diverge — use the rendered dimensions for layout and the pixel dimensions for raster operations.

:kind is:

  • :jpeg — DCTDecode filter; :bytes are the raw JPEG-encoded bytes (passthrough — suitable for writing directly to a .jpg file).
  • :png_like — FlateDecode+predictor; :bytes are decompressed pixel data (consumer must supply header information to reconstitute a PNG).

:ref is the {obj_num, gen_num} pair of the XObject in the PDF. Use it to de-duplicate images that appear on multiple pages (they share the same XObject reference).

Spec references

Summary

Types

kind()
t()

Types

Link to this type

kind()

View Source 
@type kind() :: :jpeg | :png_like
Link to this type

t()

View Source 
@type t() :: %Pdf.Reader.Image{
  bytes: binary() | nil,
  ctm: {float(), float(), float(), float(), float(), float()},
  height: float() | nil,
  kind: kind() | nil,
  page: pos_integer() | nil,
  ref: {pos_integer(), non_neg_integer()} | nil,
  render_height: float(),
  render_width: float(),
  rotation_radians: float(),
  width: float() | nil,
  x: float(),
  y: float()
}