How to resize video

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Alessandro Clocchiatti
评论： Image Analyst 2020-11-25
Hi all, I have to create a program that allows me to resize a video by 50%. Does somebody have any tips? How could I set the code?

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回答（4 个）

Image Analyst
Image Analyst 2017-1-31
See my attached demo. In the loop over frame, just resize the frame just read in and write it out with writeVideo(). If you can't figure it out, let me know what frame size you want your output in.
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Abdullah
Abdullah 2020-10-15
编辑：Image Analyst 2020-10-15
Here these two files are good. I ran them, but I am looking for video resizing in dimensions, not in resolution.
Image Analyst
Image Analyst 2020-10-15
Not sure what that means. Image frames have a certain number of pixels across (wide) and high (tall). If you reduce those, you will reduce both the pixel size across and tall, as well as the spatial resolution (meters per pixel) in real world units, meaning the ability to distinguish between two points in meters (or whatever unit you're using). Increasing the number of pixels will give you more pixels across and tall but will not increase the real world spatial resolution, meaning that you'll have more pixels per meter, but how close two points can be and still be resolved will not be changed.

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Takuji Fukumoto
Takuji Fukumoto 2017-1-30
imresize function is fine. Here is the example.
vidobj = vision.VideoFileReader('moviename')
viewer = vision.DeployableVideoPlayer;
while (1)
A = step(vidobj);
viewframe = imresize(A,0.5);
step(viewer, viewframe);
end
release(vidobj);
release(viewer);
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Alessandro Clocchiatti
Alessandro Clocchiatti 2017-1-31
Hey takij, believe me, you've been really helpful. I have one last question for you, how can i save the function?
Wenxuan Liang
Wenxuan Liang 2020-8-31
While(1)?~?!!?!?!

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Takuji Fukumoto
Takuji Fukumoto 2017-1-31
I think you can write like this
function myfunc()
%code
end
In this example, imresize is used in function. https://jp.mathworks.com/help/releases/R2016b/vision/examples/tracking-pedestrians-from-a-moving-car.html?lang=en
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Alessandro Clocchiatti
Alessandro Clocchiatti 2017-2-2
Including "videoFWriter = vision.VideoFileWriter" in the loop, the VideoWriter function didn't work. Could you tell me why?
Takuji Fukumoto
Takuji Fukumoto 2017-2-2
Not in the loop. When you use system object, you should use step function. This is a sample code to save file.
% Set up the reader and writer objects.
videoFReader = vision.VideoFileReader('viplanedeparture.mp4');
videoFWriter = vision.VideoFileWriter('myFile.avi','FrameRate',...
videoFReader.info.VideoFrameRate);
Write the first 50 frames from original file into a newly created AVI file.
for i=1:50
videoFrame = step(videoFReader);
step(videoFWriter,videoFrame);
end
%%Close the input and output files.
release(videoFReader);
release(videoFWriter);

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Abdullah Amer Mohammed Salih
Thanks for your code, I need to change video in dimentions means the video for example is 100 x 100 it will be 30 x30. that is a liniear transformation.
I also need to change the shape of the video means I change it from rectangle to polygon for example. any clue how I do that?
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Abdullah Amer Mohammed Salih
Abdullah Amer Mohammed Salih 2020-11-25
Please check the vote now,
Can you explain to me how to change the shape of mask?
I saw the function that you put at the end of the code MakeHeart, how it should be if it is any other shape? can you share the concept?
Thanks a lot
Image Analyst
Image Analyst 2020-11-25
Thanks.
You can make whatever list of (x,y) coordinates you want. Or you can just start with a binary image (mask) that you got from thresholding or wherever.
Are you going to be
  1. creating a mask from a list of (x,y) coordinates (in which case you'll use poly2mask), or
  2. creating a mask by some other means, like thresholding or some other image segmentation method?
If you need help, attach either the list of (x,y) coordinates in a .mat file with the paper clip icon, or attach the mask image itself.

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