Firstly, i am sorry if the question is stupid. I'm beginner with python opencv and image processing.
I created a program in order to read the video as the input and save it into the pgm format.
import cv2
vidcap = cv2.VideoCapture('input_video.mp4')
success,image = vidcap.read()
count = 0
while success:
cv2.imwrite("frame%d.pgm" % count, image) # save frame as PGM file
success,image = vidcap.read()
print('Read a new frame: ', success)
count += 1
vidcap.release()
After running i have the frames which seem not exactly the format of PGM image. The "magic number" is "F6" instead of "F5" of PGM format. As i know the "magic number" of PPM format (it maybe call PGM 'color', a lowest common denominator color image file format) is "F6". I don't understand why i cannot have exactly PGM image in this case. Can someone figure me out this question and give me a solution to have the PGM format frames in output ?
The video (I don't know how to upload video here, so i attack the link). I tested with this video and even with its gray-scale version but the "magic number" is always "F6".
In SO, i found this link that may be similar to my question but it is for C++.
Your image will be colour, so you will need to convert to greyscale before you can save it as PGM - meaning "Portable Grey Map":
# Convert to grey
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
# Write to disk
cv2.imwrite("frame%d.pgm" % count, gray)
By the way, IMHO it is normally a bad idea to repeat code that is doing the same thing in different places - it makes a maintenance nightmare. Rather than this where you do vidcap.read() twice:
success,image = vidcap.read()
...
while success:
cv2.imwrite("frame%d.pgm" % count, image)
success,image = vidcap.read()
consider using this so you only read the video in one place and there is only one place to add/change parameters:
while True:
success,image = vidcap.read()
if not success:
break
cv2.imwrite("frame%d.pgm" % count, image)