Remove the black bars from the edges of thumbnails

Occassionally after you finish thumbnailing a video you’ll see annoying black bars at the edges of your thumbnails. Videos that have black bars on their top and bottom are letterboxed, those with the bars on the left and right are pillarboxed , and those rare ones with bars on all sides are windowboxed. Clearly we want to remove these bars from the thumbnails since they are wasting valuable image space.

Cropping letterboxed videos

“Letterboxed” Thumbnails

In order to crop a letterboxed video you specify an aspect ratio to the -p, --crop option that is larger (wider) than the actual video frame’s aspect ratio. This chops off parts of the top and bottom of the video.

If you look at the full-size image of the above thumbnail page by clicking on it, you’ll see that it says 320x240 (1.33:1) in the upper-right corner, which is the video frame size and its aspect ratio.

You have to use trial and error to determine the correct cropping aspect ratio, but in general you should first try one of the ratios suggested here. A good place to start is to assume that the video really has an 1.85 aspect ratio. To keep a little bit of the black border — and make sure we haven’t overcropped — we should therefore use 1.81 (about 98% of 1.85) as the argument to the -p, --crop option:

cd "C:\McLintock (1963)\letterboxed"
clatn -v- --crop 1.81 McLintock_512kb_letterboxed.wmv

During the testing phase you don’t need to thumbnail the entire movie. Just type Ctrl+C to abort CLAutoThumbnailer after the first few Detail thumbnail pages have been created.

Letterboxed Video Cropped to 1.81 Aspect Ratio

While this is better the black bars are still there. So try again assuming that the video’s aspect ratio is really 2.35. Again we adjust it down a little bit to avoid overcropping:

clatn -v- --crop 2.30 McLintock_512kb_letterboxed.wmv

Letterboxed Video Cropped to 2.30 Aspect Ratio

If you view the full-size image, you’ll see that there is just a tiny bit of black now showing at the top of each thumbnail so 2.30 is the correct cropping aspect ratio to use.

Also notice that the upper right of the thumbnail page now says 320x139 (2.30:1) [320x240 (1.33:1)]. When you have two values for the frame size and aspect ratio — one inside square brackets — it means the thumbnails are created from something other than the original video frames. The dimensions inside the square brackets are the original dimensions and aspect ratio, while the other numbers are the actual frame and aspect ratio used to create the thumbnails. While these thumbnails use the entire 320 pixel width, they only use 139 of the total 240 pixel height (thus indicating that the top and bottom of the video have been cropped out to make the thumbnails).

Cropping pillarboxed videos

“Pillarboxed” Thumbnails

In order to crop a pillarboxed video you specify an aspect ratio to the -p, --crop option that is smaller (narrower) than the actual video frame’s aspect ratio. This chops off the sides of the video.

If you look at the full-size image of the above thumbnail page by clicking on it, you’ll see that it says 320x180 (1.78:1) in the upper-right corner, which is the video frame size and its aspect ratio.

Again using trial and error to determine the correct cropping aspect ratio, you should first try one of the ratios suggested here. Since the only recommended aspect ratio listed that is smaller than 1.78 is 1.33 let’s try that. When cropping pillarboxed videos you have to adjust this up a bit to keep a little bit of the black border — and make sure we haven’t overcropped. We should therefore use 1.36 (about 102% of 1.33) as the argument to the -p, --crop option:

cd "C:\His Girl Friday (1940)\pillarboxed"
clatn -v- --crop 1.36 his_girl_friday_512kb_pillarboxed.wmv

Pillarboxed Video Cropped to 1.36 Aspect Ratio

If you view the full-size image, you’ll see that there is just a small amount of black now remaining on the sides of each thumbnail so 1.36 is the correct cropping aspect ratio to use.

Also notice that the upper right of the thumbnail page now says 245x180 (1.36:1) [320x180 (1.78:1)]. While these thumbnails use the entire 180 pixel height, they only use 245 of the total 320 pixel width (thus indicating the sides of the video have been cropped out to make the thumbnails).

Cropping windowboxed videos

“Windowboxed” Thumbnails

In order to crop a windowboxed video you have to specify the exact rectangle you want to use for thumbnails with the --rect option. The -p, --crop option automatically calculates this rectangle for you given the desired aspect ratio. Using --rect gives you complete flexibility for specifying the location of this rectangle at the expense of having to figure out what that rectangle should be.

The easiest way to determine this rectangle is to first use some program to take a screenshot from the video, being sure it’s the same size as the original. Using BS.Player, you right-click the video, choose Capture frame (screenshot) ‣ Original size (P). For example:

Windowboxed Screenshot (320x240 pixels)

Then you need to somehow determine the position of the upper-left corner and the width and height of the actual Video Region. Some programs will tell you the coordinates of the current position of the cursor. You can use that information to also calculate the Video Region’s width and height.

Another techniques is to load up the screenshot in any image editing program, select just the actual video frame (ignoring the black borders), and copy/paste the video region into a new file. You’ll now have something like this:

Video Region of Windowboxed Screenshot (238x183 pixels)

and it’s easy to determine the width and height.

Next, you have to do a tiny bit of math. First we need to make sure that the Video Region still has the same aspect ratio as the original video:

Video Region Width = Video Region Height * Screenshot Aspect Ratio
Video Region Width = 183 * (320 / 240)
Video Region Width = 244

so Video Region Width = 244. Assuming that the Video Region is centered within the full video frame (it almost always is), the X location of the upper-left corner of the cropping rectangle is:

x = (Screenshot Width - Video Region Width) / 2
x = (320 - 244) / 2
x = 38

so x = 38. The Y location of the upper-left corner of the cropping rectangle is:

y = (Screenshot Height - Video Region Height) / 2
y = (240 - 183) / 2
y = 28.5

so y = 28.5 which rounds to y = 29.

The --rect option takes its argument in the form of X,Y+WIDTHxHEIGHT, therefore to thumbnail this windowboxed video we need to do the following:

cd "C:\His Girl Friday (1940)\windowboxed"
clatn -v- --rect "38,29+244x183" his_girl_friday_512kb_windowboxed.wmv

Fixed “Windowboxed” Thumbnails

If you view the full-size image, you’ll see that there is just a small amount of black remaining around each thumbnail.

Also notice that the upper right of the corrected thumbnail page says 244x183 (1.33:1) [320x240 (1.33:1)]. So these thumbnails use only 244 of the total 320 pixel width, and only 183 of the total 240 pixel height (thus indicating that parts of the video have been cropped out while making the thumbnails). The aspect ratio has correctly not been changed from 1.33.