Opencv-Python 图像透视变换cv2.warpPerspective

# -*- coding:utf-8 -*-
import cv2
import numpy as np
import sys

img = cv2.imread('test.jpg')
# cv2.imshow("original", img)

# 可选，扩展图像，保证内容不超出可视范围
img = cv2.copyMakeBorder(img, 200, 200, 200, 200, cv2.BORDER_CONSTANT, 0)
w, h = img.shape[0:2]

anglex = 0
angley = 30
anglez = 0  # 是旋转
fov = 42
r = 0

def rad(x):
    return x * np.pi / 180

def get_warpR():
    global anglex,angley,anglez,fov,w,h,r
    # 镜头与图像间的距离，21为半可视角，算z的距离是为了保证在此可视角度下恰好显示整幅图像
    z = np.sqrt(w ** 2 + h ** 2) / 2 / np.tan(rad(fov / 2))
    # 齐次变换矩阵
    rx = np.array([[1, 0, 0, 0],
                   [0, np.cos(rad(anglex)), -np.sin(rad(anglex)), 0],
                   [0, -np.sin(rad(anglex)), np.cos(rad(anglex)), 0, ],
                   [0, 0, 0, 1]], np.float32)

    ry = np.array([[np.cos(rad(angley)), 0, np.sin(rad(angley)), 0],
                   [0, 1, 0, 0],
                   [-np.sin(rad(angley)), 0, np.cos(rad(angley)), 0, ],
                   [0, 0, 0, 1]], np.float32)

    rz = np.array([[np.cos(rad(anglez)), np.sin(rad(anglez)), 0, 0],
                   [-np.sin(rad(anglez)), np.cos(rad(anglez)), 0, 0],
                   [0, 0, 1, 0],
                   [0, 0, 0, 1]], np.float32)

    r = rx.dot(ry).dot(rz)

    # 四对点的生成
    pcenter = np.array([h / 2, w / 2, 0, 0], np.float32)

    p1 = np.array([0, 0, 0, 0], np.float32) - pcenter
    p2 = np.array([w, 0, 0, 0], np.float32) - pcenter
    p3 = np.array([0, h, 0, 0], np.float32) - pcenter
    p4 = np.array([w, h, 0, 0], np.float32) - pcenter

    dst1 = r.dot(p1)
    dst2 = r.dot(p2)
    dst3 = r.dot(p3)
    dst4 = r.dot(p4)

    list_dst = [dst1, dst2, dst3, dst4]

    org = np.array([[0, 0],
                    [w, 0],
                    [0, h],
                    [w, h]], np.float32)

    dst = np.zeros((4, 2), np.float32)

    # 投影至成像平面
    for i in range(4):
        dst[i, 0] = list_dst[i][0] * z / (z - list_dst[i][2]) + pcenter[0]
        dst[i, 1] = list_dst[i][1] * z / (z - list_dst[i][2]) + pcenter[1]

    warpR = cv2.getPerspectiveTransform(org, dst)
    return warpR

def control():
    global anglex,angley,anglez,fov,r

    # 键盘控制
    if 27 == c:  # Esc quit
        sys.exit()
    if c == ord('w'):
        anglex += 1
    if c == ord('s'):
        anglex -= 1
    if c == ord('a'):
        angley += 1
        print(angley)
        # dx=0
    if c == ord('d'):
        angley -= 1
    if c == ord('u'):
        anglez += 1
    if c == ord('p'):
        anglez -= 1
    if c == ord('t'):
        fov += 1
    if c == ord('r'):
        fov -= 1
    if c == ord(' '):
        anglex = angley = anglez = 0
    if c == ord('e'):
        print("======================================")
        print('Rotation Matrix:')
        print(r)
        print('angle alpha(anglex):')
        print(anglex)
        print('angle beta(angley):')
        print(angley)
        print('dz(anglez):')
        print(anglez)


while True:

    warpR = get_warpR()

    result = cv2.warpPerspective(img, warpR, (h, w))
    cv2.namedWindow('result',2)
    cv2.imshow("result", result)
    c = cv2.waitKey(30)
    control()

cv2.destroyAllWindows()

运行效果：

控制：

• s控制垂直方向上的形变
• a和d控制水平方向上的行变
  
• u和p控制角度旋转
• e 输出当前旋转矩阵参数