A decoder for the canvas binary format of spec/09 §4 and §5, written against the record layouts the specification states — not against the encoder — so that decode(encode(x)) is a genuine round trip (D-36).

decode/1 returns the records of a stream in order:

• {:path, [{x, y}]}, {:path_cubic, [command]} with Visualize.IR.Path commands, and {:path32, [{x, y}]}, {:path_cubic32, [command]} for the f32 records (D-73), and {:cubic_run, {x0, y0}, [{x1, y1, x2, y2, x, y}]} for the cubic run (D-74)
• {:circles, [{cx, cy, r}]}, {:rects, [{x, y, w, h}]}
• {:style, %{fill:, stroke:, stroke_width:, opacity:}} (nil for an absent field), with fill_paint: and stroke_paint: indexes under bits 5 and 6
• {:effect, :shadow, radius, {dx, dy}, {r, g, b, a}} and {:effect, :blur, radius} (§4.3.14)
• {:motion, json} and :motion_end, a motion span and its end (§4.3.15, §4.3.16, #653)
• the version 3 record {:paint_state, %{fill_alpha:, stroke_alpha:, cap:, join:, dash:}}, nil for an absent field (§4.3.17, #675)
• the version 2 records {:version, v}, {:paint, index, %{type:, geometry: [f32], stops: [{at, {r, g, b, a}}]}} and {:box, {x, y, w, h}} (spec/09 §4.3.11–4.3.13)
• {:transform, :translate, {tx, ty}}, {:transform, :translate_scale, {tx, ty, sx, sy}}, {:transform, :matrix, {a, b, c, d, e, f}}

• the version 4 records {:clip, :inside | :outside} and {:blend, word}, the word the CSS mix-blend-mode one (§4.3.18, §4.3.19, #788)

• :save, :restore, :fill, :stroke
• {:incremental, mode, dx, dy, {x, y, w, h}, [{{x, y, w, h}, records}]} and {:full_redraw, viewport, records} for the 0x60 records of Visualize.Backend.CanvasIncremental

An unknown opcode or a truncated record raises, since either is an encoder bug.