详解在OpenCV中如何使用图像像素

# 切片字母列表
letters = ['a', 'b', 'c', 'd', 'e']
 
# 头三个字母
first_three = letters[:3]
 
# 最后三个字母
last_three = letters[-3:]
 
# 得到第二个到第四个字母
second_to_fourth = letters[1:4]
 
# 显示结果
print('First three letters: ', first_three)
print('Last three letters: ', last_three)
print('Second to fourth letters: ', second_to_fourth)

# 导入matplotlib的plot
import matplotlib.pyplot as plt
 
# 加载和显示原始图像
image = plt.imread('Flag_of_Ghana.png')
 
# 显示图片
plt.imshow("Original", image)
plt.plot()

if we get y1, y2 = [145, 295] and x1, x2 = [245, 400]

black_star = image[145:295, 245:400]

# 导入matplotlib的plot
import matplotlib.pyplot as plt
 
# 加载和显示原始图像
image = plt.imread('Flag_of_Ghana.png')
 
# 显示图片
plt.imshow("Original", image)
plt.plot()

# 获取图像的空间尺寸
# 初始化
originY, originX = 0, 0
 
# 获取图像的高度和宽度
height, width = image.shape[:2]
 
# 计算图像的中心
(centerX, centerY) = (width // 2, height // 2)
print('Image height: ', height)
print('Image width: ', width)
print('Center location: ', (centerY, centerX))

# 裁剪图像的左上角
# 高度从原点到中心
# 宽度从原点到中心
 
top_left = image[originY:centerY, originX:centerX]
cv2.imshow("Top-Left Corner", top_left)
cv2.waitKey(0)

# 裁剪右上角
# 高度从原点到中心
# 宽度从中心到右上角(宽度)
 
top_right = image[originY:centerY, centerX:width]
cv2.imshow("Top-Right Corner", top_right)
cv2.waitKey(0)

# 裁剪左下角
# 高度从中心到左下角(高度)
# 宽度从中心到右上角(宽度)
 
bottom_left = image[centerY:height, originX:centerX]
cv2.imshow("Bottom-Left Corner", bottom_left)
cv2.waitKey(0)

# 裁剪右下角
# 高度从中心到左下角(高度)
# 宽度从中心到右上角(宽度)
 
bottom_right = image[centerY:height, centerX:width]
cv2.imshow("Bottom-Right Corner", bottom_right)
cv2.waitKey(0)

# 设置原始图像的左上角为绿色
image[originY:centerY, originX:centerX] = (0, 255, 0)
 
# 显示更新后的图像
cv2.imshow("Updated", image)
cv2.waitKey(0)