golang-image/draw/scale.go

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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:generate go run gen.go
package draw
import (
"image"
"image/color"
"math"
"golang.org/x/image/math/f64"
)
// Copy copies the part of the source image defined by src and sr and writes to
// the part of the destination image defined by dst and the translation of sr
// so that sr.Min translates to dp.
func Copy(dst Image, dp image.Point, src image.Image, sr image.Rectangle, opts *Options) {
mask, mp, op := image.Image(nil), image.Point{}, Over
if opts != nil {
// TODO: set mask, mp and op.
}
dr := sr.Add(dp.Sub(sr.Min))
DrawMask(dst, dr, src, sr.Min, mask, mp, op)
}
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>
2015-03-03 06:54:53 +01:00
// Scaler scales the part of the source image defined by src and sr and writes
// to the part of the destination image defined by dst and dr.
//
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>
2015-03-03 06:54:53 +01:00
// A Scaler is safe to use concurrently.
type Scaler interface {
Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, opts *Options)
}
// Transformer transforms the part of the source image defined by src and sr
// and writes to the part of the destination image defined by dst and the
// affine transform m applied to sr.
//
// For example, if m is the matrix
//
// m00 m01 m02
// m10 m11 m12
//
// then the src-space point (sx, sy) maps to the dst-space point
// (m00*sx + m01*sy + m02, m10*sx + m11*sy + m12).
//
// A Transformer is safe to use concurrently.
type Transformer interface {
Transform(dst Image, m *f64.Aff3, src image.Image, sr image.Rectangle, opts *Options)
}
// Options are optional parameters to Copy, Scale and Transform.
//
// A nil *Options means to use the default (zero) values of each field.
type Options struct {
// TODO: add fields a la
// https://groups.google.com/forum/#!topic/golang-dev/fgn_xM0aeq4
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>
2015-03-03 06:54:53 +01:00
}
// Interpolator is an interpolation algorithm, when dst and src pixels don't
// have a 1:1 correspondence.
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>
2015-03-03 06:54:53 +01:00
//
// Of the interpolators provided by this package:
// - NearestNeighbor is fast but usually looks worst.
// - CatmullRom is slow but usually looks best.
// - ApproxBiLinear has reasonable speed and quality.
//
// The time taken depends on the size of dr. For kernel interpolators, the
// speed also depends on the size of sr, and so are often slower than
// non-kernel interpolators, especially when scaling down.
type Interpolator interface {
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>
2015-03-03 06:54:53 +01:00
Scaler
Transformer
}
// Kernel is an interpolator that blends source pixels weighted by a symmetric
// kernel function.
type Kernel struct {
// Support is the kernel support and must be >= 0. At(t) is assumed to be
// zero when t >= Support.
Support float64
// At is the kernel function. It will only be called with t in the
// range [0, Support).
At func(t float64) float64
}
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>
2015-03-03 06:54:53 +01:00
// Scale implements the Scaler interface.
func (q *Kernel) Scale(dst Image, dr image.Rectangle, src image.Image, sr image.Rectangle, opts *Options) {
q.NewScaler(dr.Dx(), dr.Dy(), sr.Dx(), sr.Dy()).Scale(dst, dr, src, sr, opts)
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>
2015-03-03 06:54:53 +01:00
}
// NewScaler returns a Scaler that is optimized for scaling multiple times with
// the same fixed destination and source width and height.
func (q *Kernel) NewScaler(dw, dh, sw, sh int) Scaler {
return &kernelScaler{
kernel: q,
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>
2015-03-03 06:54:53 +01:00
dw: int32(dw),
dh: int32(dh),
sw: int32(sw),
sh: int32(sh),
horizontal: newDistrib(q, int32(dw), int32(sw)),
vertical: newDistrib(q, int32(dh), int32(sh)),
}
}
var (
// NearestNeighbor is the nearest neighbor interpolator. It is very fast,
// but usually gives very low quality results. When scaling up, the result
// will look 'blocky'.
NearestNeighbor = Interpolator(nnInterpolator{})
// ApproxBiLinear is a mixture of the nearest neighbor and bi-linear
// interpolators. It is fast, but usually gives medium quality results.
//
// It implements bi-linear interpolation when upscaling and a bi-linear
// blend of the 4 nearest neighbor pixels when downscaling. This yields
// nicer quality than nearest neighbor interpolation when upscaling, but
// the time taken is independent of the number of source pixels, unlike the
// bi-linear interpolator. When downscaling a large image, the performance
// difference can be significant.
ApproxBiLinear = Interpolator(ablInterpolator{})
// BiLinear is the tent kernel. It is slow, but usually gives high quality
// results.
BiLinear = &Kernel{1, func(t float64) float64 {
return 1 - t
}}
// CatmullRom is the Catmull-Rom kernel. It is very slow, but usually gives
// very high quality results.
//
// It is an instance of the more general cubic BC-spline kernel with parameters
// B=0 and C=0.5. See Mitchell and Netravali, "Reconstruction Filters in
// Computer Graphics", Computer Graphics, Vol. 22, No. 4, pp. 221-228.
CatmullRom = &Kernel{2, func(t float64) float64 {
if t < 1 {
return (1.5*t-2.5)*t*t + 1
}
return ((-0.5*t+2.5)*t-4)*t + 2
}}
// TODO: a Kaiser-Bessel kernel?
)
type nnInterpolator struct{}
type ablInterpolator struct{}
type kernelScaler struct {
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>
2015-03-03 06:54:53 +01:00
kernel *Kernel
dw, dh, sw, sh int32
horizontal, vertical distrib
}
// source is a range of contribs, their inverse total weight, and that ITW
// divided by 0xffff.
type source struct {
i, j int32
invTotalWeight float64
invTotalWeightFFFF float64
}
// contrib is the weight of a column or row.
type contrib struct {
coord int32
weight float64
}
// distrib measures how source pixels are distributed over destination pixels.
type distrib struct {
// sources are what contribs each column or row in the source image owns,
// and the total weight of those contribs.
sources []source
// contribs are the contributions indexed by sources[s].i and sources[s].j.
contribs []contrib
}
// newDistrib returns a distrib that distributes sw source columns (or rows)
// over dw destination columns (or rows).
func newDistrib(q *Kernel, dw, sw int32) distrib {
scale := float64(sw) / float64(dw)
halfWidth, kernelArgScale := q.Support, 1.0
// When shrinking, broaden the effective kernel support so that we still
// visit every source pixel.
if scale > 1 {
halfWidth *= scale
kernelArgScale = 1 / scale
}
// Make the sources slice, one source for each column or row, and temporarily
// appropriate its elements' fields so that invTotalWeight is the scaled
// co-ordinate of the source column or row, and i and j are the lower and
// upper bounds of the range of destination columns or rows affected by the
// source column or row.
n, sources := int32(0), make([]source, dw)
for x := range sources {
center := (float64(x)+0.5)*scale - 0.5
i := int32(math.Floor(center - halfWidth))
if i < 0 {
i = 0
}
j := int32(math.Ceil(center + halfWidth))
if j > sw {
j = sw
if j < i {
j = i
}
}
sources[x] = source{i: i, j: j, invTotalWeight: center}
n += j - i
}
contribs := make([]contrib, 0, n)
for k, b := range sources {
totalWeight := 0.0
l := int32(len(contribs))
for coord := b.i; coord < b.j; coord++ {
t := abs((b.invTotalWeight - float64(coord)) * kernelArgScale)
if t >= q.Support {
continue
}
weight := q.At(t)
if weight == 0 {
continue
}
totalWeight += weight
contribs = append(contribs, contrib{coord, weight})
}
totalWeight = 1 / totalWeight
sources[k] = source{
i: l,
j: int32(len(contribs)),
invTotalWeight: totalWeight,
invTotalWeightFFFF: totalWeight / 0xffff,
}
}
return distrib{sources, contribs}
}
// abs is like math.Abs, but it doesn't care about negative zero, infinities or
// NaNs.
func abs(f float64) float64 {
if f < 0 {
f = -f
}
return f
}
// ftou converts the range [0.0, 1.0] to [0, 0xffff].
func ftou(f float64) uint16 {
i := int32(0xffff*f + 0.5)
if i > 0xffff {
return 0xffff
}
if i > 0 {
return uint16(i)
}
return 0
}
// fffftou converts the range [0.0, 65535.0] to [0, 0xffff].
func fffftou(f float64) uint16 {
i := int32(f + 0.5)
if i > 0xffff {
return 0xffff
}
if i > 0 {
return uint16(i)
}
return 0
}
// invert returns the inverse of m.
//
// TODO: move this into the f64 package, once we work out the convention for
// matrix methods in that package: do they modify the receiver, take a dst
// pointer argument, or return a new value?
func invert(m *f64.Aff3) f64.Aff3 {
m00 := +m[3*1+1]
m01 := -m[3*0+1]
m02 := +m[3*1+2]*m[3*0+1] - m[3*1+1]*m[3*0+2]
m10 := -m[3*1+0]
m11 := +m[3*0+0]
m12 := +m[3*1+0]*m[3*0+2] - m[3*1+2]*m[3*0+0]
det := m00*m11 - m10*m01
return f64.Aff3{
m00 / det,
m01 / det,
m02 / det,
m10 / det,
m11 / det,
m12 / det,
}
}
func matMul(p, q *f64.Aff3) f64.Aff3 {
return f64.Aff3{
p[3*0+0]*q[3*0+0] + p[3*0+1]*q[3*1+0],
p[3*0+0]*q[3*0+1] + p[3*0+1]*q[3*1+1],
p[3*0+0]*q[3*0+2] + p[3*0+1]*q[3*1+2] + p[3*0+2],
p[3*1+0]*q[3*0+0] + p[3*1+1]*q[3*1+0],
p[3*1+0]*q[3*0+1] + p[3*1+1]*q[3*1+1],
p[3*1+0]*q[3*0+2] + p[3*1+1]*q[3*1+2] + p[3*1+2],
}
}
// transformRect returns a rectangle dr that contains sr transformed by s2d.
func transformRect(s2d *f64.Aff3, sr *image.Rectangle) (dr image.Rectangle) {
ps := [...]image.Point{
{sr.Min.X, sr.Min.Y},
{sr.Max.X, sr.Min.Y},
{sr.Min.X, sr.Max.Y},
{sr.Max.X, sr.Max.Y},
}
for i, p := range ps {
sxf := float64(p.X)
syf := float64(p.Y)
dx := int(math.Floor(s2d[0]*sxf + s2d[1]*syf + s2d[2]))
dy := int(math.Floor(s2d[3]*sxf + s2d[4]*syf + s2d[5]))
// The +1 adjustments below are because an image.Rectangle is inclusive
// on the low end but exclusive on the high end.
if i == 0 {
dr = image.Rectangle{
Min: image.Point{dx + 0, dy + 0},
Max: image.Point{dx + 1, dy + 1},
}
continue
}
if dr.Min.X > dx {
dr.Min.X = dx
}
dx++
if dr.Max.X < dx {
dr.Max.X = dx
}
if dr.Min.Y > dy {
dr.Min.Y = dy
}
dy++
if dr.Max.Y < dy {
dr.Max.Y = dy
}
}
return dr
}
func transform_Uniform(dst Image, dr, adr image.Rectangle, d2s *f64.Aff3, src *image.Uniform, sr image.Rectangle, op Op) {
switch dst := dst.(type) {
case *image.RGBA:
pr, pg, pb, pa := src.C.RGBA()
pr8 := uint8(pr >> 8)
pg8 := uint8(pg >> 8)
pb8 := uint8(pb >> 8)
pa8 := uint8(pa >> 8)
for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
dyf := float64(dr.Min.Y+int(dy)) + 0.5
d := dst.PixOffset(dr.Min.X+adr.Min.X, dr.Min.Y+int(dy))
for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx, d = dx+1, d+4 {
dxf := float64(dr.Min.X+int(dx)) + 0.5
// TODO: change the src origin so that we can say int(f) instead of int(math.Floor(f)).
sx0 := int(math.Floor(d2s[0]*dxf + d2s[1]*dyf + d2s[2]))
sy0 := int(math.Floor(d2s[3]*dxf + d2s[4]*dyf + d2s[5]))
if !(image.Point{sx0, sy0}).In(sr) {
continue
}
dst.Pix[d+0] = pr8
dst.Pix[d+1] = pg8
dst.Pix[d+2] = pb8
dst.Pix[d+3] = pa8
}
}
default:
pr, pg, pb, pa := src.C.RGBA()
dstColorRGBA64 := &color.RGBA64{
uint16(pr),
uint16(pg),
uint16(pb),
uint16(pa),
}
dstColor := color.Color(dstColorRGBA64)
for dy := int32(adr.Min.Y); dy < int32(adr.Max.Y); dy++ {
dyf := float64(dr.Min.Y+int(dy)) + 0.5
for dx := int32(adr.Min.X); dx < int32(adr.Max.X); dx++ {
dxf := float64(dr.Min.X+int(dx)) + 0.5
// TODO: change the src origin so that we can say int(f) instead of int(math.Floor(f)).
sx0 := int(math.Floor(d2s[0]*dxf + d2s[1]*dyf + d2s[2]))
sy0 := int(math.Floor(d2s[3]*dxf + d2s[4]*dyf + d2s[5]))
if !(image.Point{sx0, sy0}).In(sr) {
continue
}
dst.Set(dr.Min.X+int(dx), dr.Min.Y+int(dy), dstColor)
}
}
}
}