Open the video file with this program (right click, search "Open with" and choose the program), you can also open it by opening the program and dragging the file to it. Read from left to right:
With the video already playing, you can capture the frame you want or need by clicking the button at the top called "Video" and choose the "Capture screen" option. There will be no need to use the "Print Pet Sis" button and then trim the image with an external program (MS Paint or Photoshop).
Once the screenshot is taken, a thumbnail and the address where it is saved will be displayed in the upper left of the video. Images taken are saved with the original dimensions of the video, that is, no matter if you get the capture with the screen maximized or not, the dimensions of the capture will always be the same as the original video. In addition it gives you in PNG format (without loss of data).
The address where VLC saves the default screenshots is in "My Pictures".
To summarize what Wikipedia says, the aspect ratio simply means the geometric relationship between the length of the width with respect to height.
For example, the screens we use today have an aspect ratio of 16:9.
It could happen that you download a video where the aspect ratio is incongruous with the original image.
For example, it happened to me that when I got Ultimate Book of Spells - EP22, its aspect ratio was 16:9, which is incompatible with a series that was created in an age (generation) previous to the televisions with that aspect ratio, that is, it was created to be played on 4:3 aspect ratio televisions.
Note that the video image is stretched horizontally, this is evidence of its incongruous aspect ratio.
And if we get a screenshot, then it will be stretched too.
Right click on the image of the video and select the option shown on the screen. But you must be careful, because under the "Proportion" option is the "Cut" option, which will cause the image to get an aspect ratio of 4:3 by eliminating the side stripes (that is to say losing information, and that is something that we do not want, besides that retains that awful stretch).
If you chose the correct ratio, you will notice it directly in the video image.
Now proceed with capturing the screen and you will see that the captured image also has its aspect ratio corrected.
The problem with the VLC screenshoter is that it gives a random name to each capture, so if you have ordered your files alphabetically, then you will find them in chronological disorder (not following the sequence of the video).
The solution is simple: you must sort your screenshots by "date (of creation)". But for this works, your screenshots should have been taken in order while the video was running (no advances or setbacks).
Do not forget that the files should be sorted by "date" and in "ascending" order.
Select all the screenshots by clicking on the first file and, while holding down the Shift key, click on the last file.
To the first file (strictly that one) you give a new name and you will see how automatically the others will also change of name by the order in which they are. I named Dexter SE0-EP2 because "SE0" means "season 0" (so they call them pilot episodes) and "EP2" means "episode 2".
All the files I passed to a separate and isolated folder (this is so that they do not mix with the new projects that I will do). Now I proceed to upload them to the wiki. The trick that facilitates this task is to go to this place and have the files on the right half of the computer screen, then proceed with dragging them to the gray boxes with the word "Browse..." and the rest is easy.