Friday, 28 October 2011

A first bit of serendipity?

A little reflection on my discovery earlier this week ...

The idea that a "semantic" region of a photo could be indicated by a shadow so that it appears to float above the rest of the photo (blog post on Monday) was an accidental result of the fact that I was working on "treatment layers" and needed a second example of a treatment. The first had been experiments with a "rubbing" layer that would transfer painted parts of the layer under it (credit to Mike Trinder, who was the first I saw using that metaphor, in his PhD supervised by Paul Richens at the Martin Centre).

As a second treatment, I wanted to implement an algorithmic image filter that would have an effect a bit like scumbled paint finishes (interesting because those finishes blur more semantically diagrammatic boundaries in favour of rich textures). This was going to be my first pixel-shifting transformation, so I needed an example to draw on. The only example I had to hand of a context-based image filter was the Gaussian blur algorithm that I'd used to implement shadows a couple of weeks ago. This was pretty complex, so after 15 minutes exploring the code to see if I could make a scumbling version, I just thought I'd see what happens when the original shadow code was applied to my source photo. Nothing, as it turns out, because the shadow was calculated from the alpha channel, and the photographic test image had a uniform alpha. Fortunately, the rubbing layer I'd just implemented didn't have a uniform alpha, so I used that instead. This visually transformed the appearance of rubbing into floating patches of picture. I then played around with superimposing these on various backgrounds in order to see them better. When superimposed on the original picture, this resulted in the appearance of a "semantic" layer that had been specified by the previous user interaction of rubbing (the user naturally rubs areas that are "interesting" for some reason).

Serendipity relies on the observer being prepared to recognise the novel occurrence. In this case, my recognition of the potential application was prompted by one of the images I had created in my own PhD experiments. There, I had made a number of photographs of playground equipment look more "diagrammatic" by rendering some of the picture elements in higher contrast over a reduced contrast background layer of the original photo.

In my discovery on Monday, it had turned out that the shadows were easier to see if a further alpha-blended white layer was rendered between the photo and the shadow. This happened to create a similar contrast-reducing effect as in my PhD experiment, and resulted in the "rubbed" elements seeming clearly diagrammatic.

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