diff --git a/src/numpy_pandas/signal_processing.py b/src/numpy_pandas/signal_processing.py
index 0fe8e2c..52223e0 100644
--- a/src/numpy_pandas/signal_processing.py
+++ b/src/numpy_pandas/signal_processing.py
@@ -90,15 +90,10 @@ def histogram_equalization(image: np.ndarray) -> np.ndarray:
     height, width = image.shape
     total_pixels = height * width
     histogram = np.zeros(256, dtype=int)
-    for y in range(height):
-        for x in range(width):
-            histogram[image[y, x]] += 1
+    np.add.at(histogram, image.ravel(), 1)
     cdf = np.zeros(256, dtype=float)
     cdf[0] = histogram[0] / total_pixels
     for i in range(1, 256):
         cdf[i] = cdf[i - 1] + histogram[i] / total_pixels
-    equalized = np.zeros_like(image)
-    for y in range(height):
-        for x in range(width):
-            equalized[y, x] = np.round(cdf[image[y, x]] * 255)
-    return equalized
+    equalized = np.round(cdf[image] * 255)
+    return equalized.astype(image.dtype)