add doodle

data/1.OpenCV初阶/1.OpenCV基础/4.IO与GUI/doodle.json

+{
+    "type": "code_options",
+    "author": "huanhuilong",
+    "source": "doodle.md",
+    "notebook_enable": true
+}
\ No newline at end of file

data/1.OpenCV初阶/1.OpenCV基础/4.IO与GUI/doodle.md

+# 矩形涂鸦画板
+
+![](./doodle.png)
+
+编写一个矩形涂鸦画板，实现功能：
+
+* 鼠标左键按下拖动绘制矩形，鼠标左键弹起时完成绘制
+* 按`'c'`键清空画板
+* 按`'ESC'`键退出
+
+基本框架代码如下：
+
+```python
+import numpy as np
+import cv2 as cv
+from random import randint
+
+
+class Painter:
+    def __init__(self) -> None:
+        self.mouse_is_pressed = False
+        self.last_pos = (-1, -1)
+        self.width = 300
+        self.height = 512
+        self.img = np.zeros((self.width, self.height, 3), np.uint8)
+        self.window_name = 'painter'
+        self.color = None
+
+    def run(self):
+        print('画板，拖动鼠标绘制矩形框，按ESC退出，按c键清空画板')
+        cv.namedWindow(self.window_name)
+        cv.setMouseCallback(
+            self.window_name,
+            lambda event, x, y, flags, param: self.on_draw(
+                event, x, y, flags, param
+            )
+        )
+        while True:
+            cv.imshow(self.window_name, self.img)
+            k = cv.waitKey(1) & 0xFF
+            if k == ord('c'):
+                self.clean()
+            elif k == 27:
+                break
+
+        cv.destroyAllWindows()
+
+    def on_draw(self, event, x, y, flags, param):
+        # TODO(You): 请正确实现画板事件响应，完成功能
+
+    def clean(self):
+        cv.rectangle(self.img, (0, 0),
+                     (self.height, self.width), (0, 0, 0), -1)
+
+    def begin_draw_rectangle(self, pos1, pos2):
+        if self.color is None:
+            self.color = (randint(0, 256), randint(0, 256), randint(0, 256))
+        cv.rectangle(self.img, pos1, pos2, self.color, -1)
+
+    def end_draw_rectangle(self, pos1, pos2):
+        self.color = None
+
+
+if __name__ == '__main__':
+    p = Painter()
+    p.run()
+```
+
+以下正确实现鼠标事件，完成画板绘制逻辑的代码是？
+
+## 答案
+
+```python
+pos = (x, y)
+if event == cv.EVENT_LBUTTONDOWN:
+    self.mouse_is_pressed = True
+    self.last_pos = pos
+elif event == cv.EVENT_MOUSEMOVE:
+    if self.mouse_is_pressed == True:
+        self.begin_draw_rectangle(self.last_pos, pos)
+elif event == cv.EVENT_LBUTTONUP:
+    self.end_draw_rectangle(self.last_pos, pos)
+    self.mouse_is_pressed = False
+```
+
+## 选项
+
+### 鼠标移动事件里缺乏判断
+
+```python
+pos = (x, y)
+if event == cv.EVENT_LBUTTONDOWN:
+    self.mouse_is_pressed = True
+    self.last_pos = pos
+elif event == cv.EVENT_MOUSEMOVE:
+    self.begin_draw_rectangle(self.last_pos, pos)
+elif event == cv.EVENT_LBUTTONUP:
+    self.end_draw_rectangle(self.last_pos, pos)
+    self.mouse_is_pressed = False
+```
+
+### 鼠标按下事件里缺乏标记
+
+```python
+pos = (x, y)
+if event == cv.EVENT_LBUTTONDOWN:
+    self.last_pos = pos
+elif event == cv.EVENT_MOUSEMOVE:
+    if self.mouse_is_pressed == True:
+        self.begin_draw_rectangle(self.last_pos, pos)
+elif event == cv.EVENT_LBUTTONUP:
+    self.end_draw_rectangle(self.last_pos, pos)
+    self.mouse_is_pressed = False
+```
+
+### 鼠标按起时忘记清空标记
+
+```python
+pos = (x, y)
+if event == cv.EVENT_LBUTTONDOWN:
+    self.mouse_is_pressed = True
+    self.last_pos = pos
+elif event == cv.EVENT_MOUSEMOVE:
+    if self.mouse_is_pressed == True:
+        self.begin_draw_rectangle(self.last_pos, pos)
+elif event == cv.EVENT_LBUTTONUP:
+    self.end_draw_rectangle(self.last_pos, pos)
+```

data/1.OpenCV初阶/1.OpenCV基础/4.IO与GUI/doodle.py

 import numpy as np
 import cv2 as cv
+from random import randint
 
 
 class Painter:
-    def __init__(self, background, color) -> None:
+    def __init__(self) -> None:
         self.mouse_is_pressed = False
         self.last_pos = (-1, -1)
-        self.img = np.zeros((300, 512, 3), np.uint8)
-        self.background = background
-        self.color = color
-        self.title = '画板，拖动鼠标绘制矩形框，按ESC退出'
+        self.width = 300
+        self.height = 512
+        self.img = np.zeros((self.width, self.height, 3), np.uint8)
         self.window_name = 'painter'
+        self.color = None
 
     def run(self):
-        cv.namedWindow(self.window_name, title=self.title)
-        cv.setMouseCallback(self.window_name, lambda event, x, y,
-                            flags, param: self.draw_circle(event, x, y, flags, param))
-        while(1):
+        print('画板，拖动鼠标绘制矩形框，按ESC退出，按c键清空画板')
+        cv.namedWindow(self.window_name)
+        cv.setMouseCallback(
+            self.window_name,
+            lambda event, x, y, flags, param: self.on_draw(
+                event, x, y, flags, param
+            )
+        )
+        while True:
             cv.imshow(self.window_name, self.img)
             k = cv.waitKey(1) & 0xFF
-            if k == 27:
+            if k == ord('c'):
+                self.clean()
+            elif k == 27:
                 break
 
         cv.destroyAllWindows()
 
-    def draw_circle(self, event, x, y, flags, param):
-        current_pos = (x, y)
+    def on_draw(self, event, x, y, flags, param):
+        pos = (x, y)
         if event == cv.EVENT_LBUTTONDOWN:
             self.mouse_is_pressed = True
-            self.last_pos = current_pos
+            self.last_pos = pos
         elif event == cv.EVENT_MOUSEMOVE:
             if self.mouse_is_pressed == True:
-                cv.rectangle(self.img, self.last_pos,
-                             current_pos, (0, 255, 0), -1)
+                self.begin_draw_rectangle(self.last_pos, pos)
         elif event == cv.EVENT_LBUTTONUP:
+            self.end_draw_rectangle(self.last_pos, pos)
             self.mouse_is_pressed = False
-            cv.rectangle(self.img, self.last_pos, current_pos, (0, 255, 0), -1)
+
+    def clean(self):
+        cv.rectangle(self.img, (0, 0),
+                     (self.height, self.width), (0, 0, 0), -1)
+
+    def begin_draw_rectangle(self, pos1, pos2):
+        if self.color is None:
+            self.color = (randint(0, 256), randint(0, 256), randint(0, 256))
+        cv.rectangle(self.img, pos1, pos2, self.color, -1)
+
+    def end_draw_rectangle(self, pos1, pos2):
+        self.color = None
 
 
 if __name__ == '__main__':
-    p = Painter(background=(100, 100, 100), color=(200, 150, 50))
+    p = Painter()
     p.run()