feat(core): 扩展 API、完善日志与代码文档规范

- 公开颜色过滤与字符集限制扩展 API，修复宏路径
- 库内打印替换为 tracing 日志，清理遗留废弃代码
- 补充核心逻辑单元测试与 crate 元数据
- 开启 missing_docs 并统一 rustfmt/clippy 格式

ddddocr-core/src/utils/image_processor.rs

@@ -1,8 +1,8 @@
 //! 图像处理算法：OpenCV 风格的常用函数封装。
 
-use image::{imageops::FilterType, DynamicImage, GrayImage, ImageBuffer, Luma};
+use image::{DynamicImage, GrayImage, ImageBuffer, Luma, imageops::FilterType};
 
-use ndarray::{azip, Array2, Array3, ArrayView2, ArrayView3};
+use ndarray::{Array2, Array3, ArrayView2, ArrayView3, azip};
 use std::cmp::{max, min};
 
 // 模拟openCV
@@ -12,7 +12,7 @@ pub fn abs_diff(a: &ArrayView3<u8>, b: &ArrayView3<u8>) -> Array3<u8> {
     // 或者直接使用 zip_mut_with 处理以减少内存分配
     let mut diff = Array3::zeros(a.dim());
     azip!((res in &mut diff, &va in a, &vb in b) {
-        *res = (va as i16 - vb as i16).abs() as u8;
+        *res = va.abs_diff(vb);
     });
     diff
 }
@@ -190,3 +190,43 @@ pub fn resize_image(
     image.resize_exact(target_width, target_height, FilterType::Lanczos3)
 }
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn abs_diff_absolutes() {
+        let a = Array3::from_shape_vec((1, 1, 3), vec![10, 200, 5]).unwrap();
+        let b = Array3::from_shape_vec((1, 1, 3), vec![200, 100, 5]).unwrap();
+        let d = abs_diff(&a.view(), &b.view());
+        assert_eq!(d[[0, 0, 0]], 190);
+        assert_eq!(d[[0, 0, 1]], 100);
+        assert_eq!(d[[0, 0, 2]], 0);
+    }
+
+    #[test]
+    fn rgb_to_gray_white_is_255() {
+        let rgb = Array3::from_shape_vec((1, 1, 3), vec![255, 255, 255]).unwrap();
+        assert_eq!(rgb_to_gray(rgb.view())[[0, 0]], 255);
+    }
+
+    #[test]
+    fn min_max_loc_finds_max() {
+        let buf = ImageBuffer::<Luma<f32>, Vec<f32>>::from_fn(3, 2, |x, y| {
+            Luma([if x == 2 && y == 1 { 0.9 } else { 0.1 }])
+        });
+        let (val, loc) = min_max_loc(&buf);
+        assert_eq!(val, 0.9);
+        assert_eq!(loc, (2, 1));
+    }
+
+    #[test]
+    fn calculate_center_midpoint() {
+        assert_eq!(calculate_center((10, 20), 6, 4), (13, 22));
+    }
+
+    #[test]
+    fn rgb_to_opencv_hsv_red() {
+        assert_eq!(rgb_to_opencv_hsv(255, 0, 0), (0, 255, 255));
+    }
+}