jon.recoil.org
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tessera-viz: scaffold with percentile utilities
Add the tessera-viz library skeleton with dune-project, .mli interface,
and a working percentile function with linear interpolation. Other API
functions are stubbed with failwith for TDD iteration.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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tessera-viz/dune-project
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tessera-viz/dune-project
···
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(lang dune 3.17)
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(name tessera-viz)
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(generate_opam_files true)
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(license ISC)
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(package
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(name tessera-viz)
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(synopsis "Visualization utilities for GeoTessera embeddings")
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(description "Convert PCA components and classification results to RGBA pixel arrays. Portable — no platform-specific encoding.")
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(depends
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(ocaml (>= 5.2))
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(tessera-linalg (>= 0.1))
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(alcotest (and :with-test (>= 0.8)))))
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tessera-viz/lib/dune
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tessera-viz/lib/dune
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tessera-viz/lib/viz.ml
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tessera-viz/lib/viz.ml
···
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type rgba_image = {
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data : (int, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t;
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width : int;
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height : int;
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}
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let percentile arr p =
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let sorted = Array.copy arr in
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Array.sort Float.compare sorted;
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let n = Array.length sorted in
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let idx = p /. 100.0 *. Float.of_int (n - 1) in
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let lo = int_of_float (Float.floor idx) in
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let hi = int_of_float (Float.ceil idx) in
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let frac = idx -. Float.of_int lo in
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if lo = hi then sorted.(lo)
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else sorted.(lo) *. (1.0 -. frac) +. sorted.(hi) *. frac
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type color = { r : int; g : int; b : int }
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let pca_to_rgba _mat ~width:_ ~height:_ ?low_pct:_ ?high_pct:_ =
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failwith "TODO: pca_to_rgba"
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let color_of_hex _s =
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failwith "TODO: color_of_hex"
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let classification_to_rgba ~predictions:_ ~colors:_ ~width:_ ~height:_ ?alpha:_ =
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failwith "TODO: classification_to_rgba"
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tessera-viz/lib/viz.mli
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tessera-viz/lib/viz.mli
···
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(** Visualization utilities for GeoTessera embeddings.
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Converts PCA components and classification results to raw RGBA pixel
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arrays. Does no encoding — callers handle PNG/base64 conversion. *)
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type rgba_image = {
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data : (int, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t;
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width : int;
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height : int;
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}
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(** An RGBA image. [data] has length [width * height * 4], with pixels in
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row-major order: R, G, B, A for each pixel. *)
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(** {1 Percentile utilities} *)
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val percentile : float array -> float -> float
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(** [percentile arr p] returns the [p]-th percentile (0-100) of [arr].
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[arr] is not modified. *)
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(** {1 PCA visualization} *)
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val pca_to_rgba : Linalg.mat -> width:int -> height:int -> ?low_pct:float -> ?high_pct:float -> rgba_image
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(** Convert a 3-component PCA result to a false-color RGBA image.
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Input: mat with shape [(height*width, 3)] from [Linalg.pca_transform].
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Each component is independently clipped to [\[low_pct, high_pct\]] percentiles
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(default: 2.0, 98.0) and scaled to [0-255].
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Alpha is always 255.
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Output: RGBA image of size [width * height]. *)
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(** {1 Classification visualization} *)
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type color = { r : int; g : int; b : int }
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(** An RGB color. *)
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val color_of_hex : string -> color
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(** Parse a hex color string like ["#ff0000"] or ["ff0000"]. *)
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val classification_to_rgba :
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predictions:int array ->
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colors:(int * color) list ->
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width:int ->
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height:int ->
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?alpha:int ->
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rgba_image
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(** Convert class predictions to a colored RGBA image.
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[predictions] has length [height * width].
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[colors] maps class IDs to colors. Unknown classes are black.
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[alpha] defaults to 200. *)
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tessera-viz/test/dune
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tessera-viz/test/dune
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tessera-viz/test/test_viz.ml
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tessera-viz/test/test_viz.ml
···
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let check_float msg expected actual =
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Alcotest.(check (float 1e-6)) msg expected actual
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let test_percentile_min () =
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check_float "p0" 1.0 (Viz.percentile [|1.0; 2.0; 3.0; 4.0; 5.0|] 0.0)
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let test_percentile_max () =
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check_float "p100" 5.0 (Viz.percentile [|1.0; 2.0; 3.0; 4.0; 5.0|] 100.0)
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let test_percentile_median () =
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check_float "p50" 3.0 (Viz.percentile [|1.0; 2.0; 3.0; 4.0; 5.0|] 50.0)
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let test_percentile_unsorted () =
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check_float "p50 unsorted" 3.0 (Viz.percentile [|5.0; 1.0; 3.0; 2.0; 4.0|] 50.0)
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let percentile_tests =
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[ Alcotest.test_case "min (p0)" `Quick test_percentile_min
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; Alcotest.test_case "max (p100)" `Quick test_percentile_max
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; Alcotest.test_case "median (p50)" `Quick test_percentile_median
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; Alcotest.test_case "unsorted input" `Quick test_percentile_unsorted
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]
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let () =
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Alcotest.run "tessera-viz"
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[ ("percentile", percentile_tests)
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]