日常生活中，手残党们经常会把一些照片拍歪，比如拍个证件、试卷、PPT什么的，

比如下面这本书的封面原本是个矩形，随手一拍就成了不规则四边形

想要把它变成规则的矩形，有什么办法呢？

你一定想到了 PS，因为网上很多教程就是这么教的

打开PS $\Longrightarrow$ 滤镜 $\Longrightarrow$镜头校正 $\Longrightarrow$自定 $\Longrightarrow$变换

可是这样手工的调整数值实在是费劲哟！！

下面我们来写个程序，自动将图片恢复到任意矩形！

程序实现

1. 打开图片并显示

import cv2 as cv
import numpy as np

path = './book.jpg'
src = cv.imread(path)

def get_window_size(src, bound=600):
    h,w = src.shape[0], src.shape[1]
    if h > w:
        h, w = bound, int(w*bound/h)
    else:
        h, w = int(h*bound/w), bound
    return (h, w)

h, w = get_window_size(src)

win_name = 'RecAdjust'
cv.namedWindow(win_name, cv.WINDOW_NORMAL)
cv.resizeWindow(win_name, width=w, height=h)
cv.imshow(win_name, src)
cv.waitKey(0)
cv.destroyAllWindows()

2. 在图片中标记四个角点

src_copy = src.copy()

class Indexer:
    def __init__(self, bound=4):
        self.id = 0
        self.bound=bound
    
    def get_id(self):
        self.id = (self.id+1)%self.bound
        return (self.id-1)%self.bound+1

def on_EVENT_LBUTTONDOWN(event, x, y, flags, param):
    if event == cv.EVENT_LBUTTONDOWN:
      
        img = param['src']
        win_name = param['window']
        indexer = param['indexer']
        points = param['points']
        
        curr_id = indexer.get_id()
        points.append((x,y))
        print('第{}个顶点: ({},{})'.format(curr_id, x, y))
        
        cv.circle(img, (x, y), 10, (0, 0, 255), thickness = 2)
        cv.putText(
            img,       
            str(curr_id),           # 文字
            (x, y),                 # 坐标
            cv.FONT_HERSHEY_PLAIN,
            5,                      # 字号
            (0,0,255),              # 字体颜色
            thickness = 2           # 粗细
        )

        cv.imshow(win_name, img)

points = []
indexer = Indexer()
win_name = 'RecAdjust'
cv.namedWindow(win_name, cv.WINDOW_NORMAL)
cv.resizeWindow(win_name, width=w, height=h)
cv.imshow(win_name, src)
cv.setMouseCallback(win_name, on_EVENT_LBUTTONDOWN, param={'src':src,'window':win_name, 'indexer':indexer, 'points':points})
cv.waitKey(0)
cv.destroyAllWindows()
print(points)

3. 设定输出矩形大小

# W = int(input('输出图片宽度:'))
# H = int(input('输出图片高度:'))
W,H = 600, 800
target_points = [(0,0),(W,0),(W,H),(0,H)]

4. 求解透视变换矩阵

points, target_points = np.array(points, dtype=np.float32), np.array(target_points, dtype=np.float32)
M = cv.getPerspectiveTransform(points, target_points)
print('透视变换矩阵:',M)

5. 透视变换并保存图片

result = cv.warpPerspective(src_copy, M, (0, 0))
result = result[:H, :W]
win_name = 'Result'
cv.namedWindow(win_name, cv.WINDOW_NORMAL)
cv.resizeWindow(win_name, width=W, height=H)
cv.imshow(win_name, result)
cv.waitKey(0)
cv.destroyAllWindows()

output_file = 'result.jpg'
cv.imwrite(output_file, result)

结果如下

结果没有想象的完美，是因为书的封面已经不是一个平面了，书角翘起。。。

如果图片中的矩形在一个平面上的话，效果还是挺不错的！！

完整代码下载

可关注后免费下载喔：https://download.csdn.net/download/itnerd/12819535