The thumbnail service renders arbitrary image/video/gif thumbnails from Time Machines accessible over HTTP/HTTPS. While the thumbnail service lives on thumbnails.cmucreatelab.org, it can render thumbnails for Time Machines served anywhere over HTTP or HTTPS.
JPEG thumbnail from Earth Timelapse, from the Brazilian State of Rondonia in 2012:
http://thumbnails.cmucreatelab.org/thumbnail?root=http://earthengine.google.org/timelapse/data/20130507&boundsNWSE=-8.02999,-65.51147,-13.56390,-59.90845&width=200&frameTime=2.8
GIF thumbnail from a Shenango Coke Works smoke emission in 2014:
http://thumbnails.cmucreatelab.org/thumbnail?root=http://tiles.cmucreatelab.org/ecam/timemachines/shenango1/2014-11-20.timemachine/&boundsLTRB=2084.88990915391,1273.0414920286516,3791.489909153904,2519.6414920286475&width=320&height=240&frameTime=877.8333333333334&nframes=10&format=gif&tileFormat=mp4&labels=2014-10-06%2009:30:31
http://thumbnails.cmucreatelab.org/thumbnail?[flags]
root=rootUrl
Root URL for time machine JSON and tiles. The file tm.json should be found at rootUrl/tm.json. rootUrl should not contain a trailing ‘/’.
boundsLTRB=left,top,right,bottom
Source bounds for thumbnail, in the pixel coordinates of the time machine. Must specify either this or boundsNWSE.
boundsNWSE=north,west,south,east
Source bounds for the thumbnail, in lat/lon coordinates. Only allowed if time machine includes projection data to allow conversion from lat/lon to pixel coordinates. Must specify either this or boundsLTRB. Lat and lon are standard decimal representations, with positive lat representing north, and positive lon representing east.
width=width
Output width of thumbnail, in pixels.
Output size in pixels can be specified by either or both of width or height; the unspecified dimension will automatically be calculated based on the aspect ratio from the source rectangle (as specified by boundsLTRB or boundsNWSE). If both width and height are be provided, the source rectangle will be tweaked if needed to produce output of exactly the specified aspect ratio.
height=height
Output height of thumbnail, in pixels. Must specify one or both of width and height; see below. (Due to a limitation of ffmpeg, height of 1 pixel appears to not be supported. Use height of 2 pixels or more until we work around this.)
nframes=nframes
Optional number of frames to output. Default is 1, to output a single frame.
format=suffix
Optional output format (jpg, png, gif, mp4, webm, rgb24, zip). If omitted, defaults to jpg. mp4, webm, gif, rgb24, and zip allow multiple-frame animations. jpg and png are single-frame formats, which require nframes be omitted or set to 1. rgb24 packs output as 3 bytes per pixel (r, g, b), in row-major order. zip creates a zipfile of individual PNG-encoded frames.
delay=delay
Speed of playback, given in frames per second. By default, gifs are 20 frames per second, and videos use the fps of the source tile.
frameTime=timeInSeconds
Optional playback time for frame, in seconds. If omitted, defaults to 0 (first frame).
frameTimeEnd=timeInSeconds
Optional playback time for last frame, in seconds. Used when outputting image sequences. If omitted, frameTimeEnd is calculated from nframes based on frame rate of the original video source. 2014-March-07: NOT YET IMPLEMENTED
labels=labelList
Add labels to a single frame or multiple frames of the output file.
If you want the same label across all the frames (or if you have only one frame), you can do something like:
labels=myLabel
If you want a different label for every frame, you can do something like:
labels=firstFrameLabel|secondFrameLabel|ThirdFrameLabel|...
Note that the labels are delimited by |
If you want the same label for the first two frames, then nothing for two, then a new label, you can do this:
labels=firstFrameLabel|secondFrameLabel|||fifthFrameLabel|sixthFrameLabel
Note that we still use the | delimiter for frames where we are omitting a label.
You can also use this trick to ensure that only the first frame of a multi frame output has a label. So for example:
labels=firstFrameLabel|
This ensures that any frames after the first one does not have a label.
If you want the same label repeated for several frames, you will have to repeat it in your list.
labelsFromDataset
Related to the frame labels mentioned above and is available if you want to use labels already provided by the dataset, since every set should already have a list of capture times.
labelAttributes=labelColor|labelSize|labelXPos|labelYPos
By default labels will be yellow, 20 pixels in size, and at position 10, 10 of the output file. If you want to change any of these, you can do so with this flag. The order of attributes must be adhered and are delimited with |
If, for example, you wanted to change the label to white, size 18 and at position 100, 10, you can do something like:
labelAttributes=white|18|100|10
You do not have to provide all the attributes, but they must be in the order given above. If, for example, you want to change only the font color and the x position, then you just leave the fields in between empty. So for example:
labelAttributes=white||100|
Note that we still include the | delimiter for omitted attributes in this case.
Options you shouldn’t need to use:
debug
Optional: show debugging output from service rather than outputting an image.
recompute
Optional: force recomputation of image, even if present in cache. Please only use this for debugging or benchmarking, never in production.
test
Optional: perform regression test on service. Warning: the thumbnails on the test page set recompute to ensure bugs aren't masked by the cache. Do not use these thumbnails as example URLs unless you're very careful to remove the recompute flag!
tileFormat=format
Optional format to select from Time Machine tile source. Defaults to webm, to work around an ffmpeg seek bug. If your tile source only has mp4 files, you can try setting this to mp4.
If you want to install your own copy of the thumbnail server:
- Edit cache_dir and ffmpeg_path in thumbnail-server.rb
- Set up as a cgi script for your webserver
If you're developing on a Mac, you can run this under apache on your mac; look at apache-config-examples/osx-rsargent.conf and follow the comments at the top of that file to customize and install.