cdbd68f34f
If both dimensions are given, always use those dimensions, avoiding roundoff error. If only one dimension is given, slightly prefer rounding the other dimension up, to rounding it down.
145 lines
4.4 KiB
Go
145 lines
4.4 KiB
Go
/*
|
|
Copyright (c) 2012, Jan Schlicht <jan.schlicht@gmail.com>
|
|
|
|
Permission to use, copy, modify, and/or distribute this software for any purpose
|
|
with or without fee is hereby granted, provided that the above copyright notice
|
|
and this permission notice appear in all copies.
|
|
|
|
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
|
|
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
|
|
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
|
|
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
|
|
OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
|
|
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
|
|
THIS SOFTWARE.
|
|
*/
|
|
|
|
// Package resize implements various image resizing methods.
|
|
//
|
|
// The package works with the Image interface described in the image package.
|
|
// Various interpolation methods are provided and multiple processors may be
|
|
// utilized in the computations.
|
|
//
|
|
// Example:
|
|
// imgResized := resize.Resize(1000, 0, imgOld, Lanczos3)
|
|
package resize
|
|
|
|
import (
|
|
"image"
|
|
"image/color"
|
|
"runtime"
|
|
)
|
|
|
|
// Trans2 is a 2-dimensional linear transformation.
|
|
type Trans2 [6]float32
|
|
|
|
// Apply the transformation to a point (x,y).
|
|
func (t *Trans2) Eval(x, y float32) (u, v float32) {
|
|
u = t[0]*x + t[1]*y + t[2]
|
|
v = t[3]*x + t[4]*y + t[5]
|
|
return
|
|
}
|
|
|
|
// Filter can interpolate at points (x,y)
|
|
type Filter interface {
|
|
Interpolate(x, y float32) color.RGBA64
|
|
}
|
|
|
|
// InterpolationFunction return a Filter implementation
|
|
// that operates on an image. Two factors
|
|
// allow to scale the filter kernels in x- and y-direction
|
|
// to prevent moire patterns.
|
|
type InterpolationFunction func(image.Image, [2]float32) Filter
|
|
|
|
// Resize an image to new width and height using the interpolation function interp.
|
|
// A new image with the given dimensions will be returned.
|
|
// If one of the parameters width or height is set to 0, its size will be calculated so that
|
|
// the aspect ratio is that of the originating image.
|
|
// The resizing algorithm uses channels for parallel computation.
|
|
func Resize(width, height uint, img image.Image, interp InterpolationFunction) image.Image {
|
|
oldBounds := img.Bounds()
|
|
oldWidth := float32(oldBounds.Dx())
|
|
oldHeight := float32(oldBounds.Dy())
|
|
|
|
scaleX, scaleY := calcFactors(width, height, oldWidth, oldHeight)
|
|
t := Trans2{scaleX, 0, float32(oldBounds.Min.X), 0, scaleY, float32(oldBounds.Min.Y)}
|
|
|
|
resizedImg := image.NewRGBA64(image.Rect(0, 0, int(0.7+oldWidth/scaleX), int(0.7+oldHeight/scaleY)))
|
|
b := resizedImg.Bounds()
|
|
|
|
n := numJobs(b.Dy())
|
|
c := make(chan int, n)
|
|
for i := 0; i < n; i++ {
|
|
go func(b image.Rectangle, c chan int) {
|
|
filter := interp(img, [2]float32{clampFactor(scaleX), clampFactor(scaleY)})
|
|
var u, v float32
|
|
var color color.RGBA64
|
|
for y := b.Min.Y; y < b.Max.Y; y++ {
|
|
for x := b.Min.X; x < b.Max.X; x++ {
|
|
u, v = t.Eval(float32(x), float32(y))
|
|
//resizedImg.SetRGBA64(x, y, filter.Interpolate(u, v))
|
|
color = filter.Interpolate(u, v)
|
|
i := resizedImg.PixOffset(x, y)
|
|
resizedImg.Pix[i+0] = uint8(color.R >> 8)
|
|
resizedImg.Pix[i+1] = uint8(color.R)
|
|
resizedImg.Pix[i+2] = uint8(color.G >> 8)
|
|
resizedImg.Pix[i+3] = uint8(color.G)
|
|
resizedImg.Pix[i+4] = uint8(color.B >> 8)
|
|
resizedImg.Pix[i+5] = uint8(color.B)
|
|
resizedImg.Pix[i+6] = uint8(color.A >> 8)
|
|
resizedImg.Pix[i+7] = uint8(color.A)
|
|
}
|
|
}
|
|
c <- 1
|
|
}(image.Rect(b.Min.X, b.Min.Y+i*(b.Dy())/n, b.Max.X, b.Min.Y+(i+1)*(b.Dy())/n), c)
|
|
}
|
|
|
|
for i := 0; i < n; i++ {
|
|
<-c
|
|
}
|
|
|
|
return resizedImg
|
|
}
|
|
|
|
// Calculate scaling factors using old and new image dimensions.
|
|
func calcFactors(width, height uint, oldWidth, oldHeight float32) (scaleX, scaleY float32) {
|
|
if width == 0 {
|
|
if height == 0 {
|
|
scaleX = 1.0
|
|
scaleY = 1.0
|
|
} else {
|
|
scaleY = oldHeight / float32(height)
|
|
scaleX = scaleY
|
|
}
|
|
} else {
|
|
scaleX = oldWidth / float32(width)
|
|
if height == 0 {
|
|
scaleY = scaleX
|
|
} else {
|
|
scaleY = oldHeight / float32(height)
|
|
}
|
|
}
|
|
return
|
|
}
|
|
|
|
// Set filter scaling factor to avoid moire patterns.
|
|
// This is only useful in case of downscaling (factor>1).
|
|
func clampFactor(factor float32) (r float32) {
|
|
r = factor
|
|
if r < 1 {
|
|
r = 1
|
|
}
|
|
return
|
|
}
|
|
|
|
// Set number of parallel jobs
|
|
// but prevent resize from doing too much work
|
|
// if #CPUs > width
|
|
func numJobs(d int) (n int) {
|
|
n = runtime.NumCPU()
|
|
if n > d {
|
|
n = d
|
|
}
|
|
return
|
|
}
|