Thumbnail Page Layout Modes

The Problem

Other thumbnailing programs typically let you specify the thumbnail width (or height) and the number of columns (or rows) you want. Then they automatically determine the required size of the thumbnail page.

The problem with this approach is that video aspect ratios can vary widely from about 1.33 to 2.35 and beyond — and therefore so can the aspect ratios of the generated thumbnail pages.

This isn’t so much of a problem as long as the resulting thumbnail page’s aspect ratio is the about the same or less than your viewing monitor’s aspect ratio. If it’s about the same, the page will be displayed with little “wasting” of pixels.

Thumbnail Page Aspect Ratio Similar to Monitor Aspect Ratio

If the thumbnail page’s aspect ratio is significantly smaller (narrower) than your monitor’s, there can be many pixels wasted to the sides of the thumbnails when viewing the page in “Fit Image”/”Fit to Window” mode. Switching to “Fit Width” somewhat solves this problem, by only requiring you to scroll down through the page to view the thumbnails in the proper order.

Thumbnail Page Aspect Ratio Narrower Than Monitor Aspect Ratio

“Fit to Window” Viewing Mode	“Fit Width” Viewing Mode

If the thumbnail page’s aspect ratio is significantly greater (wider) than your monitor’s, however, you get tiny thumbnails when in “Fit Image”/”Fit to Window” mode and waste lots of pixels above and below the thumbnails. Worse, switching to “Fit Height” now requires you to constantly scroll back and forth to see the thumbnails in the proper order. Not a very desirable activity.

Thumbnail Page Aspect Ratio Wider Than Monitor Aspect Ratio

“Fit to Window” Viewing Mode	“Fit Height” Viewing Mode

The Solution

Instead of this “bottom-up” approach to thumbnail page generation, CLAutoThumbnailer takes a “top-down” approach. You specify the approximate thumbnail page dimensions you want (under the assumption that you know in general what monitor you will be viewing the pages on). Then given the number of rows (or columns) you’d prefer, CLAutoThumbnailer automatically tries to determine the best number of columns (or rows) that will fit within your desired thumbnail page aspect ratio.

It does this by using two basic approaches, Row Priority Layout and Column Priority Layout, with a third, Auto Layout, automatically switching between the other two.

Either way, the goal is to create a thumbnail page whose aspect ratio is as similar to the target aspect ratio as possible.

Here’s the general thumbnail page layout options:

-y, --layout=MODE          layout MODE
                             (0=Auto,1=Actual,2=Row Priority,3=Column
                             Priority) [Auto]
    --othres=THRESHOLD     video aspect ratio THRESHOLD for
                             Auto Layout of Overview Page [0.00]
    --dthres=THRESHOLD     video aspect ratio THRESHOLD for
                             Auto Layout of Detail Pages [0.00]
-n=ROWS or COLUMNS         Overview page desired # of ROWS or COLUMNS [12]
-N=ROWS or COLUMNS         Detail page desired # of ROWS or COLUMNS [4]

Row/Column Optimization

With any layout except Actual Layout, if the calculated number of columns or rows results in wasting a percentage of the thumbnail width or height that is over a threshold, the number is adjusted by adding 1. This behavior can be turned off by using the --rcopt option.

Here’s all the Row/Column Optimization options:

--rcopt                do row/column optimizations
                         (–rcopt- disables) [True]
--maxoptsteps=STEPS    max # of row/column optimization STEPS
                         (0=unlimited) [2]
--wthres=THRESHOLD     width THRESHOLD for adding columns (0.1 - 1.0)
                         [0.60]
--hthres=THRESHOLD     height THRESHOLD for adding rows (0.1 - 1.0)
                         [0.60]
--mincols=COLUMNS      minimum # of COLUMNS [3]
--minrows=ROWS         minimum # of ROWS [3]

Row Priority Layout

With Row Priority layout CLAutoThumbnailer respects the number of rows requested and automatically calculates the number of columns to use based on the aspect ratio of the video and the aspect ratio of the thumbnail page.

The height of generated thumbnail pages will always be close to the requested height but the desired width is only approximated.

This is generally the best layout mode to use since it keeps the thumbnail height the same even as the video frame gets wider or narrower.

Row Priority Layout Mode - Row/Column Optimization Disabled

Row Priority Layout Mode

Column Priority Layout

With Column Priority layout CLAutoThumbnailer respects the number of columns requested and automatically calculates the number of rows to use based on the aspect ratio of the video and the aspect ratio of the thumbnail page.

The width of generated thumbnail pages will always be close to the requested width but the desired height is only approximated.

Column Priority Layout Mode - Row/Column Optimization Disabled

Column Priority Layout Mode - Calculated Columns and Rows

Auto Layout

With Auto Layout CLAutoThumbnailer normally uses Row Priority Layout but automatically switches to Column Priority Layout when the video aspect ratio drops below a certain threshold.

Auto Layout Mode - Row/Column Optimization Disabled

Row Priority Layout Mode - Row/Column Optimization Disabled

Auto Layout Mode - Calculated Columns and Rows

Actual Layout

With Actual Layout CLAutoThumbnailer respects both the number of columns and rows requested. It ignores any wastage this might cause.

If the aspect ratio of the video frame is smaller than the aspect ratio of the desired thumbnail page, then the height of the video frame will be fit inside the height of the thumbnail page (taking into account the header). Otherwise, the width of the video frame is fit within the width of the thumbnail page.