muesli/smartcrop — pull request #10 by swenson (2014-12-01 03:14:07+00:00)
Title: Precompute CIE values in edge detection for 2x speedup

When running the test benchmark, I noticed that the dominant step was often edge detection. Upon investigation, it looked like there might be a lot of redundant calculations going on there. So I wrote a quick benchmark, and confirmed that precomputing the CIE values into a slice and reusing them saves a lot of time.

Benchmark results:

```
benchmark old ns/op new ns/op delta
BenchmarkEdge 192006874 78530474 -59.10%
```