三张图片拼接在一起的整体尺寸大于单张图片的总和，为什么？

Question

以下代码获取来自三个 USB 摄像头的输入，并将它们组合成一张宽图像，并存储为一个 .AVI 文件。

szPlacename = 'Station A'
iCaptureDuration = 600
iFramesPerSec = 3
szFramesPerSec = str(iFramesPerSec)

# Create VideoCapture objects for all three cameras
cap0 = cv2.VideoCapture(0)
cap1 = cv2.VideoCapture(1)
cap2 = cv2.VideoCapture(2)

# Set the pause duration during application execution (in seconds)
iSleepDuration = 0

# Set the frame width and height
iFrameWidth = 1024
iFrameHeight = 768
szFrameWidth = str(iFrameWidth)
szFrameHeight = str(iFrameHeight)

# Define a smaller size for displaying on the screen
iDisplayWidth = 400
iDisplayHeight = 300

# Get the computer name
szComputerName = socket.gethostname()

# Calculate percentage remaining hard drive space
iTotal, iUsed, iFree = shutil.disk_usage("/")
iPercent = 100 * iUsed / iTotal
iPercent = round(iPercent, 1)
szPercent = str(iPercent) + "%"
# Set up font for text display on frames
font = cv2.FONT_HERSHEY_COMPLEX_SMALL
# Check if cameras opened successfully
if not all([cap0.isOpened(), cap1.isOpened(), cap2.isOpened()]):
     print("Unable to read camera feed")
# Create directory structure for saving videos
output_path = pathlib.Path('C:\\LZ\\') / f"{szPlacename}-{datetime.datetime.now().strftime('%Y%m%d')}"
output_path.mkdir(parents=True, exist_ok=True)
# Set up VideoWriter object for recording
out = cv2.VideoWriter(
    str(output_path / f"{datetime.datetime.now().strftime('%Y%m%d%H%M%S')}_{szPlacename}_StarLink.avi"),
    cv2.VideoWriter_fourcc('M', 'J', 'P', 'G'),
    iFramesPerSec, (iFrameWidth * 3, iFrameHeight)
)
# Capture video for the specified duration
iStartTime = time.time()
while int(time.time() - iStartTime) < iCaptureDuration:
    ret0, frame0 = cap0.read()
    ret1, frame1 = cap1.read()
    ret2, frame2 = cap2.read()

    if not all([ret0, ret1, ret2]):
        break

    szDateTime = str(datetime.datetime.now())
    szDateTime = szDateTime[0:22]

    # Resize frames for display
    display_frame0 = imutils.resize(frame0, width=iDisplayWidth)
    display_frame1 = imutils.resize(frame1, width=iDisplayWidth)
    display_frame2 = imutils.resize(frame2, width=iDisplayWidth)

    # Resize frames for storage
    # Descriptive text only in frame 0
    frame0 = imutils.resize(frame0, width=iFrameWidth)
    frame0 = cv2.putText(frame0, f"Laptop: " + szComputerName + ", HD used= " + szPercent + ", FPS= " + szFramesPerSec + ", Size(px)= " + szFrameWidth + "x" + szFrameHeight, (10, 30), font, 0.5, (0, 0, 0), 1, cv2.LINE_8)# black
    frame0 = cv2.putText(frame0, f"Location: " + szPlacename + ", Time: " + szDateTime,(10, 60), font, 0.5, (0, 0, 0), 1, cv2.LINE_8)# black
    frame0 = cv2.putText(frame0, f"Laptop: " + szComputerName + ", HD used= " + szPercent + ", FPS= " + szFramesPerSec + ", Size(px)= " + szFrameWidth + "x" + szFrameHeight, (10, 90), font, 0.5, (0, 255, 255), 1, cv2.LINE_8)# yellow
    frame0 = cv2.putText(frame0, f"Location: " + szPlacename + ", Time: " + szDateTime,(10, 120), font, 0.5, (0, 255, 255), 1, cv2.LINE_8)# yellow
    
    frame1 = imutils.resize(frame1, width=iFrameWidth)
    frame2 = imutils.resize(frame2, width=iFrameWidth)

# Add text to display frames
    display_frame0 = cv2.putText(display_frame0, f"Laptop: " + szComputerName + ", HD used= " + szPercent + ", FPS= " + szFramesPerSec + ", Size(px)= " + szFrameWidth + "x" + szFrameHeight, (10, 30), font, 0.5, (0, 0, 0), 1, cv2.LINE_8)# black
    display_frame0 = cv2.putText(display_frame0, f"Location: " + szPlacename + ", Time: " + szDateTime,(10, 60), font, 0.5, (0, 0, 0), 1, cv2.LINE_8)# black
    display_frame0 = cv2.putText(display_frame0, f"Laptop: " + szComputerName + ", HD used= " + szPercent + ", FPS= " + szFramesPerSec + ", Size(px)= " + szFrameWidth + "x" + szFrameHeight, (10, 90), font, 0.5, (0, 255, 255), 1, cv2.LINE_8)# yellow
    display_frame0 = cv2.putText(display_frame0, f"Location: " + szPlacename + ", Time: " + szDateTime,(10, 120), font, 0.5, (0, 255, 255), 1, cv2.LINE_8)# yellow
    display_frame1 = cv2.putText(display_frame1, f"Laptop: {szComputerName}", (5, 15), font, 0.5, (0, 0, 0), 1, cv2.LINE_8)
    display_frame2 = cv2.putText(display_frame2, f"Laptop: {szComputerName}", (5, 15), font, 0.5, (0, 0, 0), 1, cv2.LINE_8)

    # Combine frames horizontally
    combined_frame = np.hstack([display_frame0, display_frame1, display_frame2])

    # Display frames
    cv2.imshow('Three Cameras Side by Side (Display)', combined_frame)

    # Write original resolution frames to the video
    out.write(np.hstack([frame0, frame1, frame2]))

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# Release resources
cap0.release()
cap1.release()
cap2.release()
out.release()
cv2.destroyAllWindows()

奇怪的是，当使用单个 USB 摄像头制作 AVI 文件时，文件大小约为 180MB。然而，当三个 USB 摄像头组合在一起时，创建的文件比预期大得多，通常超过 1.5GB。为什么是这样？预先感谢。

Answer 1

这解决了问题。组合图像现在等于各个图像的总和。

import cv2
import numpy as np
import time
import datetime
import pathlib
import imutils
import socket

szPlacename = 'Station A'
iCaptureDuration = 30
iFramesPerSec = 3
iFrameWidth, iFrameHeight = 1024, 768
iDisplayWidth, iDisplayHeight = 1200, 300

cap0, cap1, cap2 = cv2.VideoCapture(0), cv2.VideoCapture(1),    cv2.VideoCapture(2)

out_combined = cv2.VideoWriter(f'C:\\LZ\\{szPlacename}-  {datetime.datetime.now():%Y%m%d}/'
                          f'{datetime.datetime.now():%Y%m%d%H%M%S} {szPlacename}_Combined.avi',
                          cv2.VideoWriter_fourcc('m', 'j', 'p', 'g'), iFramesPerSec, (iFrameWidth * 3, iFrameHeight))

iPrev = 0
iStartTime = time.time()
while int(time.time() - iStartTime) < iCaptureDuration:
iTimeElapsed = time.time() - iPrev
while iTimeElapsed > 1. / iFramesPerSec:
    ret0, frame0 = cap0.read()
    ret1, frame1 = cap1.read()
    ret2, frame2 = cap2.read()
    if not all([ret0, ret1, ret2]):
        break
    if iTimeElapsed > 1. / iFramesPerSec:
        iPrev = time.time()
        szDateTime = str(datetime.datetime.now())[0:22]
    if ret0:
        frames = [imutils.resize(frame, width=iFrameWidth) for frame in [frame0, frame1, frame2]]
        combined_frame = np.hstack(frames)
        resized_combined_frame = cv2.resize(combined_frame, (iDisplayWidth, iDisplayHeight))
        cv2.imshow('Three Cameras Side by Side (Display)', resized_combined_frame)
        out_combined.write(np.hstack(frames))
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
    else:
        break

# Release resources
cap0.release()
cap1.release()
cap2.release()
out_combined.release()
cv2.destroyAllWindows()