commit 8e3389fa81abf8e318abefa17054df807e5c5692
author Nigel Tao <nigeltao@golang.org> Fri Jul 31 18:09:14 2015 +1000
committer Nigel Tao <nigeltao@golang.org> Sun Aug 02 10:47:07 2015 +0000
tree 866b80a0c418e68f8a06e90032960170fee7ad3c
parent 5ec5e003b21ac1f06e175898413ada23a6797fc0

draw: have Scale and Transform recognize straight copies.

This is only for the NearestNeighbor and ApproxBiLinear Interpolators. A
Kernel interpolator will add blur even when the dst and src rectangles
are the same size.

We do not bother recognizing Transforms that are Scales. The performance
difference is minimal, as you still need to do a per-dst-pixel inverse
mapping either way.

benchmark                           old ns/op     new ns/op     delta
BenchmarkSimpleScaleCopy-8          4866297       29586         -99.39%
BenchmarkSimpleTransformCopy-8      4875991       29531         -99.39%
BenchmarkSimpleTransformScale-8     1208147       1223206       +1.25%

Change-Id: If649ad27a4e81bcbb24b18315745c02c9186a5b7
Reviewed-on: https://go-review.googlesource.com/13004
Reviewed-by: Rob Pike <r@golang.org>