feat(core): 阶梯色阶 colorAt+颜色解析(alpha 量纲按来源)

src/core/CMakeLists.txt

@@ -2,6 +2,7 @@ find_package(Eigen3 CONFIG REQUIRED)
 
 add_library(geopro_core STATIC
   geo/LocalFrame.cpp
+  model/ColorScale.cpp
 )
 
 target_include_directories(geopro_core PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})

src/core/model/ColorScale.cpp

@@ -0,0 +1,46 @@
+#define _CRT_SECURE_NO_WARNINGS  // MSVC: std::sscanf 解析颜色字符串，长度受限输入安全
+#include "model/ColorScale.hpp"
+#include <algorithm>
+#include <cmath>
+#include <cstdio>
+namespace geopro::core {
+
+static unsigned char clampByte(double v) {
+    if (v < 0) v = 0;
+    if (v > 255) v = 255;
+    return static_cast<unsigned char>(v + 0.5);
+}
+
+Rgba parseColor(const std::string& s, AlphaScale alpha) {
+    if (!s.empty() && s[0] == '#') {
+        auto hex = [&](int i) {
+            return static_cast<unsigned char>(std::stoi(s.substr(static_cast<size_t>(i), 2), nullptr, 16));
+        };
+        return Rgba{hex(1), hex(3), hex(5), 255};
+    }
+    double r = 0, g = 0, b = 0, a = 1;
+    auto p = s.find('(');
+    if (p != std::string::npos) {
+        std::sscanf(s.c_str() + p, "(%lf,%lf,%lf,%lf", &r, &g, &b, &a);
+    }
+    unsigned char av = (alpha == AlphaScale::Unit) ? clampByte(a * 255.0) : clampByte(a);
+    return Rgba{clampByte(r), clampByte(g), clampByte(b), av};
+}
+
+void ColorScale::addStop(double value, Rgba color) {
+    stops_.push_back({value, color});
+    std::sort(stops_.begin(), stops_.end(),
+              [](const Stop& x, const Stop& y) { return x.value < y.value; });
+}
+
+Rgba ColorScale::colorAt(double value) const {
+    if (std::isnan(value)) return nan_.value_or(Rgba{0, 0, 0, 0});
+    if (stops_.empty()) return Rgba{0, 0, 0, 0};
+    if (value < stops_.front().value) return under_.value_or(stops_.front().color);
+    if (value >= stops_.back().value) return over_.value_or(stops_.back().color);
+    auto it = std::upper_bound(stops_.begin(), stops_.end(), value,
+                               [](double v, const Stop& s) { return v < s.value; });
+    return (it == stops_.begin() ? stops_.front() : *(it - 1)).color;
+}
+
+}  // namespace geopro::core

src/core/model/ColorScale.hpp

@@ -0,0 +1,27 @@
+#pragma once
+#include <string>
+#include <vector>
+#include <optional>
+namespace geopro::core {
+
+struct Rgba { unsigned char r, g, b, a; };
+enum class AlphaScale { Unit, Bit255 };  // rgba alpha 量纲：0-1 或 0-255
+
+Rgba parseColor(const std::string& s, AlphaScale alpha = AlphaScale::Bit255);
+
+// 阶梯色阶：值落 [stop_i, stop_{i+1}) 取 stop_i 的颜色（与平台一致）。
+class ColorScale {
+public:
+    void addStop(double value, Rgba color);  // 内部保持按 value 升序
+    Rgba colorAt(double value) const;        // 含 under/over/NaN 处理
+    void setUnder(Rgba c) { under_ = c; }
+    void setOver(Rgba c)  { over_ = c; }
+    void setNan(Rgba c)   { nan_ = c; }
+    bool empty() const { return stops_.empty(); }
+private:
+    struct Stop { double value; Rgba color; };
+    std::vector<Stop> stops_;
+    std::optional<Rgba> under_, over_, nan_;
+};
+
+}  // namespace geopro::core

tests/CMakeLists.txt

@@ -11,6 +11,7 @@ gtest_discover_tests(geopro_tests)
 
 target_sources(geopro_tests PRIVATE core/test_local_frame.cpp)
 target_sources(geopro_tests PRIVATE core/test_model.cpp)
+target_sources(geopro_tests PRIVATE core/test_color_scale.cpp)
 target_link_libraries(geopro_tests PRIVATE geopro_core)
 
 add_subdirectory(spike)   # spike S3: banded contour 渲染验证

tests/core/test_color_scale.cpp

@@ -0,0 +1,29 @@
+#include <gtest/gtest.h>
+#include "model/ColorScale.hpp"
+using namespace geopro::core;
+
+TEST(ColorScale, SteppedLookupTakesLowerStop) {
+    ColorScale cs;
+    cs.addStop(0.0,  Rgba{0,0,255,255});
+    cs.addStop(10.0, Rgba{0,255,0,255});
+    cs.addStop(20.0, Rgba{255,0,0,255});
+    EXPECT_EQ(cs.colorAt(5.0).g, 0);     // [0,10) -> 蓝
+    EXPECT_EQ(cs.colorAt(5.0).b, 255);
+    EXPECT_EQ(cs.colorAt(15.0).r, 0);    // [10,20) -> 绿
+    EXPECT_EQ(cs.colorAt(15.0).g, 255);
+}
+
+TEST(ColorScale, UnderOverHandling) {
+    ColorScale cs; cs.addStop(0.0, Rgba{0,0,0,255}); cs.addStop(10.0, Rgba{255,255,255,255});
+    cs.setUnder(Rgba{1,2,3,255}); cs.setOver(Rgba{4,5,6,255});
+    EXPECT_EQ(cs.colorAt(-1.0).r, 1);    // under
+    EXPECT_EQ(cs.colorAt(99.0).r, 4);    // over
+}
+
+TEST(ColorScale, ParseHexAndRgba) {
+    EXPECT_EQ(parseColor("#0000B3").b, 0xB3);
+    auto c255 = parseColor("rgba(0,0,170,255)", AlphaScale::Bit255);
+    EXPECT_EQ(c255.b, 170); EXPECT_EQ(c255.a, 255);
+    auto c1 = parseColor("rgba(0,0,170,1)", AlphaScale::Unit);
+    EXPECT_EQ(c1.b, 170); EXPECT_EQ(c1.a, 255);  // 0-1 的 1.0 -> 255
+}