如何比较视频的第一帧和其他帧

Question

import cv2
cap = cv2.VideoCapture(input_path)
count = 0
n=0
while True:
ret, frame = cap.read()

if ret:
# You can do processing on this frame variabqle
roi = frame[343:489, 572:759]
#         frame = cv2.resize(roi, None, fx=0.9, fy=0.9)

cv2.imshow("roi", roi)


cv2.imshow("image", frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break


cv2.destroyAllWindows()

我想将视频的第一帧与其他视频帧进行比较，并基于第一帧计算ssim(相似度)。如何做这个搜索很多，但没有得到想要的结果。

Answer 1

@Ceopee是正确的，教程中没有错误。

这个想法很简单:

if count is 0
get the first frame
else
calculate ssim of frame1 and the next-frame
display

代码:

---

import cv2
import numpy as np

def ssim(i1, i2):
c1 = 6.5025
c2 = 58.5225
# INITS
I1 = np.float32(i1) # cannot calculate on one byte large values
I2 = np.float32(i2)
I2_2 = I2 * I2 # I2^2
I1_2 = I1 * I1 # I1^2
I1_I2 = I1 * I2 # I1 * I2
# END INITS
# PRELIMINARY COMPUTING
mu1 = cv2.GaussianBlur(I1, (11, 11), 1.5)
mu2 = cv2.GaussianBlur(I2, (11, 11), 1.5)
mu1_2 = mu1 * mu1
mu2_2 = mu2 * mu2
mu1_mu2 = mu1 * mu2
sigma1_2 = cv2.GaussianBlur(I1_2, (11, 11), 1.5)
sigma1_2 -= mu1_2
sigma2_2 = cv2.GaussianBlur(I2_2, (11, 11), 1.5)
sigma2_2 -= mu2_2
sigma12 = cv2.GaussianBlur(I1_I2, (11, 11), 1.5)
sigma12 -= mu1_mu2
t1 = 2 * mu1_mu2 + c1
t2 = 2 * sigma12 + c2
t3 = t1 * t2                    # t3 = ((2*mu1_mu2 + C1).*(2*sigma12 + C2))
t1 = mu1_2 + mu2_2 + c1
t2 = sigma1_2 + sigma2_2 + c2
t1 = t1 * t2                    # t1 =((mu1_2 + mu2_2 + C1).*(sigma1_2 + sigma2_2 + C2))
ssim_map = cv2.divide(t3, t1)    # ssim_map =  t3./t1;
mssim = cv2.mean(ssim_map)       # mssim = average of ssim map
return mssim

cap = cv2.VideoCapture("b/ex.mp4")
count = 0
frm1 = -1
cv2.namedWindow("frame-1")
cv2.moveWindow("frame-1", 800, 0)
while cap.isOpened():
ret, frm = cap.read()
if ret:
if count == 0:
frm1 = frm
else:
mssimv = ssim(frm1, frm)
print("nMSSISM: R {}% G {}% B {}%".format(round(mssimv[2] * 100, 2), round(mssimv[1] * 100, 2),
round(mssimv[0] * 100, 2)), end=" ")
cv2.imshow("frame-1", frm1)
cv2.imshow("frame-{}".format(count), frm)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
count += 1
else:
break
cap.release()
cv2.destroyAllWindows()