69 lines
1.4 KiB
Go
69 lines
1.4 KiB
Go
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// Copyright 2011 The Graphics-Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package graphics
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import (
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"code.google.com/p/graphics-go/graphics/convolve"
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"errors"
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"image"
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"image/draw"
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"math"
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)
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// DefaultStdDev is the default blurring parameter.
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var DefaultStdDev = 0.5
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// BlurOptions are the blurring parameters.
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// StdDev is the standard deviation of the normal, higher is blurrier.
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// Size is the size of the kernel. If zero, it is set to Ceil(6 * StdDev).
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type BlurOptions struct {
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StdDev float64
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Size int
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}
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// Blur produces a blurred version of the image, using a Gaussian blur.
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func Blur(dst draw.Image, src image.Image, opt *BlurOptions) error {
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if dst == nil {
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return errors.New("graphics: dst is nil")
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}
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if src == nil {
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return errors.New("graphics: src is nil")
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}
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sd := DefaultStdDev
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size := 0
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if opt != nil {
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sd = opt.StdDev
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size = opt.Size
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}
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if size < 1 {
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size = int(math.Ceil(sd * 6))
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}
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kernel := make([]float64, 2*size+1)
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for i := 0; i <= size; i++ {
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x := float64(i) / sd
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x = math.Pow(1/math.SqrtE, x*x)
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kernel[size-i] = x
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kernel[size+i] = x
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}
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// Normalize the weights to sum to 1.0.
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kSum := 0.0
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for _, k := range kernel {
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kSum += k
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}
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for i, k := range kernel {
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kernel[i] = k / kSum
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}
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return convolve.Convolve(dst, src, &convolve.SeparableKernel{
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X: kernel,
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Y: kernel,
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})
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}
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