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Nigel Tao 2c27a34d37 draw: make Scale an Interpolator method instead of a function. 
This means that only Kernel values have a NewScaler method, which
re-uses computation when scaling multiple images of the same dst and src
dimensions. The NearestNeighbor and ApproxBiLinear scalers don't get any
pre-computation to re-use, so don't need a NewScaler method just to
satisfy the previous Interpolator interface. As a small bonus, NN.Scale
and ABL.Scale should no longer allocate on the fast paths.

This change is consistent the upcoming Transformer method, so that the
Interpolator interface will be

type Interpolator interface {
	Scale(etc)
	Transform(etc)
}

instead of

type Interpolator interface {
	NewScaler(etc) Scaler
	Transform(etc)
}

I don't have a good theory for why the "func (ablInterpolator)
scale_RGBA_RGBA" benchmark is such a dramatic improvement, but at least
it's in the right direction. I'm calling the other benchmark changes as
noise.

benchmark                     old ns/op      new ns/op      delta
BenchmarkScaleLargeDownNN     3233406        3169060        -1.99%
BenchmarkScaleLargeDownAB     12018178       12011348       -0.06%
BenchmarkScaleLargeDownBL     1420827834     1409335695     -0.81%
BenchmarkScaleLargeDownCR     2820669690     2795534035     -0.89%
BenchmarkScaleDownNN          866628         869241         +0.30%
BenchmarkScaleDownAB          3175963        3216041        +1.26%
BenchmarkScaleDownBL          26639767       26677003       +0.14%
BenchmarkScaleDownCR          51720996       51621628       -0.19%
BenchmarkScaleUpNN            42758485       43258611       +1.17%
BenchmarkScaleUpAB            156693813      156943367      +0.16%
BenchmarkScaleUpBL            69511444       69621698       +0.16%
BenchmarkScaleUpCR            124530191      124885601      +0.29%
BenchmarkScaleSrcGray         8992205        9129321        +1.52%
BenchmarkScaleSrcNRGBA        9807837        9894466        +0.88%
BenchmarkScaleSrcRGBA         1333188        1104282        -17.17%
BenchmarkScaleSrcUniform      1147788        1162488        +1.28%
BenchmarkScaleSrcYCbCr        12164542       12305373       +1.16%

Change-Id: I2aee6c392eb7437e843260775aed97ce145b4d47
Reviewed-on: https://go-review.googlesource.com/6556
Reviewed-by: Rob Pike <r@golang.org>
2015-03-04 22:50:18 +00:00
bmp image: add import comments. 2014-12-09 22:43:18 +00:00
cmd/webp-manual-test image: add import comments. 2014-12-09 22:43:18 +00:00
draw draw: make Scale an Interpolator method instead of a function. 2015-03-04 22:50:18 +00:00
math math/f32, math/f64: add Aff3 and Aff4 types. 2015-03-03 04:33:37 +00:00
riff image: add import comments. 2014-12-09 22:43:18 +00:00
testdata draw: new package, a superset of the standard library's image/draw 2015-02-17 23:20:02 +00:00
tiff image: add import comments. 2014-12-09 22:43:18 +00:00
vp8 image: add import comments. 2014-12-09 22:43:18 +00:00
vp8l image: add import comments. 2014-12-09 22:43:18 +00:00
webp image: add import comments. 2014-12-09 22:43:18 +00:00
.gitattributes image: copying .gitattributes to all subrepositories 2014-12-23 11:05:35 +00:00
.gitignore convert .hgignore to .gitignore. 2014-12-08 10:42:30 +11:00
AUTHORS go.empty: prototype for new subrepository 2012-01-25 14:45:13 -05:00
CONTRIBUTING.md doc: add CONTRIBUTING.md 2015-02-20 05:00:47 +00:00
CONTRIBUTORS go.empty: prototype for new subrepository 2012-01-25 14:45:13 -05:00
LICENSE LICENSE: add 2012-03-17 15:20:31 +11:00
PATENTS go.image: add PATENTS file to the subrepo. 2012-04-16 11:25:02 +10:00
README go.image: initial code. 2012-01-31 11:32:50 +11:00

README 

This repository holds supplementary Go image libraries.

To submit changes to this repository, see http://golang.org/doc/contribute.html.