Reusable colormap facility (camp::map::ColorMap) for scalar-field layers

[rolker]

Summary

Introduce a small, reusable colormap facility in the shared map library
(camp::map::ColorMap) so scalar fields render through a selectable set of
named colormaps instead of per-subsystem hardcoded ramps.

Motivation

The camp2 map-system port (#59) drops camp's hardcoded grid_map "speed"
colormap (a situational green/red ramp) in favor of camp2's generic grayscale
auto-range default. Rather than reintroduce another one-off ramp, we want a
generic colormap component usable across camp's scalar-field renderers.

Today the same value→color pattern is reimplemented per subsystem:

• grid_map layers — currently grayscale auto-range (camp2 default after Port camp2 multi-layer + OSM/WMTS map system into deployed CAMP; retire obsoleted + dead ROS 1 code #59);
  see docs/parity/grids.md.
• depth raster shading — backgroundraster.cpp:48-62 hardcodes a
  green-land / red-by-depth ramp; see docs/parity/raster.md.

Both are natural consumers of one shared facility.

Scope

• camp::map::ColorMap in libcamp_map: a named lookup (grayscale,
  plus a few perceptually reasonable ramps, e.g. viridis, turbo) mapping a
  value + range → QColor, with optional fixed or auto range.
• Per-layer colormap selection in the layer tree (which colormap + range a
  grid_map / scalar layer uses).
• Wire grid_map layers to it; migrate depth-raster shading onto it.
• Leave OccupancyGrid on its standard 0–100 occupancy spec colormap
  (already parity, docs/parity/grids.md) unless a reason emerges to unify.

Notes

• Deferred out of Port camp2 multi-layer + OSM/WMTS map system into deployed CAMP; retire obsoleted + dead ROS 1 code #59 to keep the port moving (decision 2026-06-02): Port camp2 multi-layer + OSM/WMTS map system into deployed CAMP; retire obsoleted + dead ROS 1 code #59 lands
  grayscale grid_map; this issue designs the generic selectable facility
  properly across camp's uses.
• Part of Port camp2 multi-layer + OSM/WMTS map system into deployed CAMP; retire obsoleted + dead ROS 1 code #59 (follow-up).

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Authored-By: Claude Code Agent
Model: Claude Opus 4.8 (1M context)

[rolker]

Implemented on the #59 branch (PR #60) — camp::map::ColorMap lives in libcamp_map, which is created on that branch (PR2) and not yet on jazzy, so a standalone PR off jazzy couldn't build. Commits: 649943a (facility + 7 unit tests + grid_map wired), 7e14ad0 (grid_map per-layer selection + persistence), ccbfd2d (RasterLayer shades single-band Float32/depth rasters), c9b9744 (per-raster colormap selection).

Done:

• camp::map::ColorMap: grayscale / viridis / turbo, value+range or normalised → QColor, NaN/degenerate-range → transparent. Unit-tested (test_color_map, 7 cases).
• grid_map renders through it (default grayscale = byte-identical to the post-Port camp2 multi-layer + OSM/WMTS map system into deployed CAMP; retire obsoleted + dead ROS 1 code #59 output); per-layer colormap context menu + QSettings persistence.
• Depth-raster shading migrated onto it: a single-band Float32 raster now renders depth-shaded (default viridis, NoData transparent) instead of near-black; per-raster colormap selection + persistence.
• OccupancyGrid left on its 0–100 spec colormap, as scoped.

Closing notes carried into #59: depth-raster shading composes with the eventual depth layer there.

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Authored-By: Claude Code Agent
Model: Claude Opus 4.8 (1M context)

[rolker]

Cross-link: this is the CAMP consumer of the shared colormap effort
rolker/unh_marine_autonomy#137.

Rather than build a camp-local camp::map::ColorMap, the plan is to adopt the
shared framework-agnostic marine_colormap core (palettes incl. the
grayscale + viridis/turbo this issue wants, plus the transfer function and
per-layer range) and wrap its Rgba output to QColor in CAMP. That keeps CAMP's
scalar-field colors identical to rviz/rqt and avoids a third copy of the same
ramp logic.

This issue stays open as the CAMP-side adoption task; the shared core lands first
under rolker/unh_marine_autonomy#137.

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Authored-By: Claude Code Agent
Model: Claude Opus 4.8 (1M context)

[rolker]

Update: the umbrella moved to rolker/unh_marine_autonomy#137, and the shared lib is now a standalone repo, rolker/marine_colormap. CAMP adoption (this issue) consumes that lib's core; design in rolker/unh_marine_autonomy ADR-0001.

[rolker]

Note for the eventual GPU path of this facility (the CAMP Tier-2 colormap consumer):

The shared shader is now available — marine_colormap::colormap_glsl() (merged in marine_colormap#6) returns version-agnostic GLSL (marine_colormap_normalize / marine_colormap_response) that mirrors the CPU transfer, plus bake_lut() for a 1-D palette LUT. So when CAMP renders scalar-field layers through its GL viewport, it can colormap full-precision data on the GPU (range/gain/contrast as uniforms, palette as a LUT) rather than recoloring on the CPU.

Reference implementation: the rqt waterfall GPU consumer (rolker/rqt_operator_tools#48), including the offscreen-GL CPU/GPU parity test pattern and the "don't double-apply the transfer" contract (identity LUT + shader response, or baked LUT + no shader response, never both — see the marine_colormap README).

Not filing a separate GPU issue: that work belongs to this facility once the CPU side here lands. Flagging it so the GPU option is on record. Part of rolker/unh_marine_autonomy#137.

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Authored-By: Claude Code Agent
Model: Claude Opus 4.8 (1M context)