增加人脸识别

data/1.OpenCV初阶/5.图像识别/1.人脸识别/face_detect.md

+# 被挤压的地铁人脸检测
+
+![](./fake_face.jpeg)
+
+即使是地铁挤压的人脸，也是有尊严的，值得被检测，经过 OpenCV 的努力，成功检测：
+
+![](./rust_face_detect.jpeg)
+
+
+* 左图是正常被识别的人脸
+* 中图由于挤地铁人脸已不可识别
+* 右图OpenCV单应性变换后，拯救了被miss的人脸
+
+框架代码如下：
+
+```python
+import cv2
+import numpy as np
+
+
+def correct_rust_face():
+    img_src = cv2.imread('rust_face_src.jpeg')
+    pts_src = np.array([[0, 0], [0, 1078], [570, 0], [570, 1078]])
+
+    img_dst = cv2.imread('rust_face_dest.jpeg')
+    pts_dst = np.array([[63, 285], [84, 820], [378, 224], [427, 689]])
+
+    dw, dh = img_src.shape[1], img_src.shape[0]
+
+    h, status = cv2.findHomography(pts_dst, pts_src)
+    img_out = cv2.warpPerspective(img_dst, h, (dw, dh))
+    return img_out
+
+
+def face_detect(input_image):
+    [x, y, w, h] = [0, 0, 0, 0]
+
+    # TODO(You): 实现人脸识别
+
+    if len(face_rects) > 0:
+        for face_rect in face_rects:
+            x, y, w, h = face_rect
+            cv2.rectangle(input_image, (x, y),
+                          (x + w, y + h), [255, 255, 0], 2)
+
+
+if __name__ == '__main__':
+    [x, y, w, h] = [0, 0, 0, 0]
+
+    rust_face_src = cv2.imread('rust_face_src.jpeg')
+    face_detect(rust_face_src)
+
+    rust_face_dest = cv2.imread('rust_face_dest.jpeg')
+    face_detect(rust_face_dest)
+
+    rust_face_dest_correct = correct_rust_face()
+    face_detect(rust_face_dest_correct)
+
+    images = np.concatenate(
+        (rust_face_src[0: 1070, 0:542, 0:3], rust_face_dest, rust_face_dest_correct[0: 1070, 0:542, 0:3]), axis=1)
+    cv2.imshow('rust_face_detect', images)
+
+    cv2.waitKey(0)
+    cv2.destroyAllWindows()
+```
+
+已知 OpenCV 官方仓库里有人脸分类器模型文件""data_haarcascades_haarcascade_frontalface_alt.xml""
+
+请找出正确实现的代码。
+
+## 答案
+
+```python
+h, w = input_image.shape[:2]
+gray = cv2.cvtColor(input_image, cv2.COLOR_BGR2GRAY)
+gray = cv2.equalizeHist(gray)
+min_size = (w // 10, h // 10)
+
+face_cascade = cv2.CascadeClassifier(
+    "data_haarcascades_haarcascade_frontalface_alt.xml")
+
+face_rects = face_cascade.detectMultiScale(
+    gray, 1.05, 2, cv2.CASCADE_SCALE_IMAGE, min_size)
+```
+
+## 选项
+
+### 没有使用灰度图
+
+```python
+h, w = input_image.shape[:2]
+gray = cv2.cvtColor(input_image, cv2.COLOR_BGR2GRAY)
+gray = cv2.equalizeHist(gray)
+min_size = (w // 10, h // 10)
+
+face_cascade = cv2.CascadeClassifier(
+    "data_haarcascades_haarcascade_frontalface_alt.xml")
+
+face_rects = face_cascade.detectMultiScale(
+    input_image, 1.05, 2, cv2.CASCADE_SCALE_IMAGE, min_size)
+```
+
+### 没有使用模型
+
+```python
+h, w = input_image.shape[:2]
+gray = cv2.cvtColor(input_image, cv2.COLOR_BGR2GRAY)
+gray = cv2.equalizeHist(gray)
+min_size = (w // 10, h // 10)
+
+face_rects = cv2.detectMultiScale(
+    gray, 1.05, 2, cv2.CASCADE_SCALE_IMAGE, min_size)
+```
+
+### 参数错误
+
+```python
+h, w = input_image.shape[:2]
+gray = cv2.cvtColor(input_image, cv2.COLOR_BGR2GRAY)
+gray = cv2.equalizeHist(gray)
+
+face_cascade = cv2.CascadeClassifier(
+    "data_haarcascades_haarcascade_frontalface_alt.xml")
+
+face_rects = face_cascade.detectMultiScale(
+    gray, 1.05, 2, cv2.CASCADE_SCALE_IMAGE, w // 10, h // 10)
+```

data/1.OpenCV初阶/5.图像识别/1.人脸识别/face_detect.py

+import cv2
+import numpy as np
+
+
+def correct_rust_face():
+    img_src = cv2.imread('rust_face_src.jpeg')
+    pts_src = np.array([[0, 0], [0, 1078], [570, 0], [570, 1078]])
+
+    img_dst = cv2.imread('rust_face_dest.jpeg')
+    pts_dst = np.array([[63, 285], [84, 820], [378, 224], [427, 689]])
+
+    dw, dh = img_src.shape[1], img_src.shape[0]
+
+    h, status = cv2.findHomography(pts_dst, pts_src)
+    img_out = cv2.warpPerspective(img_dst, h, (dw, dh))
+    return img_out
+
+
+def face_detect(input_image):
+    [x, y, w, h] = [0, 0, 0, 0]
+
+    h, w = input_image.shape[:2]
+    gray = cv2.cvtColor(input_image, cv2.COLOR_BGR2GRAY)
+    gray = cv2.equalizeHist(gray)
+    min_size = (w // 10, h // 10)
+
+    face_cascade = cv2.CascadeClassifier(
+        "data_haarcascades_haarcascade_frontalface_alt.xml")
+
+    face_rects = face_cascade.detectMultiScale(
+        gray, 1.05, 2, cv2.CASCADE_SCALE_IMAGE, min_size)
+
+    if len(face_rects) > 0:
+        for face_rect in face_rects:
+            x, y, w, h = face_rect
+            cv2.rectangle(input_image, (x, y),
+                          (x + w, y + h), [255, 255, 0], 2)
+
+
+if __name__ == '__main__':
+    [x, y, w, h] = [0, 0, 0, 0]
+
+    rust_face_src = cv2.imread('rust_face_src.jpeg')
+    face_detect(rust_face_src)
+
+    rust_face_dest = cv2.imread('rust_face_dest.jpeg')
+    face_detect(rust_face_dest)
+
+    rust_face_dest_correct = correct_rust_face()
+    face_detect(rust_face_dest_correct)
+
+    images = np.concatenate(
+        (rust_face_src[0: 1070, 0:542, 0:3], rust_face_dest, rust_face_dest_correct[0: 1070, 0:542, 0:3]), axis=1)
+    # cv2.imwrite('rust_face_detect.jpeg', images)
+    cv2.imshow('rust_face_detect', images)
+
+    cv2.waitKey(0)
+    cv2.destroyAllWindows()