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68 lines
1.4 KiB
68 lines
1.4 KiB
// 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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