Slicing to make panoramas

I shot some video at the national museum a few weeks ago, and have just started having a bit of a play with it using a slicing (or slitscan) technique. It seems that the result is really dependent on getting smooth and slow coverage of the scene captured to video. There’s a relationship between points on objects and screen pixels that I’ll try to pin down more precisely soon. Basically if a point on an object matches up to a screen pixel in a frame, then on each subsequent frame it ideally moves the equivalent of 1 screen pixel with whatever camera panning/tracking occured at that point in the footage. Variations in this relationship results in stretching or compression of features in the scene across the axis of movement.

Here’s a sample panorama taken with a hand-held pan around the ‘courtyard’ of the national museum:

In this image you can see the compression along the x-axis that occurs when the camera pan was a little too fast. This can be compensated for by scaling the resultant image in photoshop on the y-axis:

Photoshop can also stretch the image along the x-axis (same effect in a bigger image), but this results in some deterioration of the image by the creation of new pixels with resampling/interpolation.

Resolution issues

For the image generated by running scan lines in 3D through the videocube, the resolution in the x-dimension for output is not a problem – there are plenty of pixels available for that. I edited a quick test image in Photoshop that was scaled in the y-dimension (but not the x). This smooths out some of the misalignments where each pass joins up.

The image get’s a bit blurry though, but maybe when printed it could look ok. I’m contemplating printing these kinds of long images from a roll of paper to go beyond the standard sheet sizes if I have to.

As for the animation option, that’s already in the processing code I’ve written by default – each pass is one call to the draw() method in processing. The output on screen is an x*t image with a duaration of y frames.

I’m not sure how far I’ll go with this particular experiment, as I have other cats to skin, but the ability to create a long image and looking at how to deal with the resolution is useful for the other things I have in mind.

That last post was cactus…

Despite the interesting effect created by the coding I made for the videocube experiment in the previous post, it was in fact ‘wrong’. I.e. it was not a correct implementation of the concept I had devised. I’ve fixed this now and it’s looking different.

I’m going to attempt to write a bunch of slices out to a file to create a reeeeaaaaalllllllllyyyyy long still picture of the slices that this generates. For example the image above which was pieced together in photoshop using screen grabs is taken from only four passes through the draw command in processing. It takes the same number of passes as the videocube has in the y-direction to do a complete cycle through, so for this image that would be 100 passes.

Another vid-cube experiment

This one takes a bit to get your head around it. Imagine a cube of video. Imagine a line drawn through the cube from the top-front-left corner to the bottom-back-right corner. Sample each pixel that intersects with the line. Draw that sampled slice as a line in the display. Now move the line end points one pixel into the cube in the x direction (so the front goes x++, back goes x–). Repeat until the line end points reach their horizontally opposite corners. The result:

The image is x wide, by t high (t = number of frames in video source).

There are a lot of options for this one considering that the line end points could be situated anywhere and cycled through any number of points in the cube.

More video cube stuff

Coded up a version that shows two views – one going sideways through the cube and the other going top down. Aesthetically the juxtaposition does nothing for me, I thought initially they could go together, but they don’t really join up too well, and they get out of sync anyway.

Look! Up in the sky!

It’s supershapes in processing.

Gotta love them JPEG artifacts…

Video slicing

I have made a video slicer in processing. It takes a single line of pixels from a quicktime movie. The line can be moved around in an interactive manner, and the slices of video appear in the sketch area below the movie display. By using 2 mice (mouses?), the line can be a vertical or a diagonal one.