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@afandian afandian/plotter.go
Created Jul 25, 2012

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A Go program that plots sound files into PNGs. Uses libdndfile + gosndfile
package main
// plotter.go
// Joe Wass 2012
// joe@afandian.com
import (
"fmt"
"image"
"image/color"
"image/png"
"log"
"os"
"sndfile"
)
// Number of seconds worth of buffer to allocate.
const Seconds = 10
// Height per channel.
const ImageHeight = 200
func main() {
if len(os.Args) < 3 {
fmt.Println("Usage: go run plotter.go /path/to/wav /path/to/png")
return
}
var info sndfile.Info
soundFile, err := sndfile.Open(os.Args[1], sndfile.Read, &info)
if err != nil {
log.Fatal("Error", err)
}
defer soundFile.Close()
imageFile, err := os.Create(os.Args[2])
if err != nil {
log.Fatal(err)
}
defer imageFile.Close()
buffer := make([]float32, Seconds*info.Samplerate*info.Channels)
numRead, err := soundFile.ReadItems(buffer)
numSamples := int(numRead/int64(info.Channels))
numChannels := int(info.Channels)
outimage := image.NewRGBA(image.Rect(0, 0, numSamples, ImageHeight * numChannels))
if err != nil {
return
}
// Both math.Abs and math.Max operate on float64. Hm.
max := float32(0)
for _, v := range buffer {
if v > max {
max = v
} else if v*-1 > max {
max = v * -1
}
}
// Work out scaling factor to normalise signaland get best use of space.
mult := float32(ImageHeight/max) / 2
// Signed float so add 1 to turn [-1, 1] into [0, 2].
for i := 0; i < numSamples; i++ {
for channel := 0; channel < numChannels; channel ++ {
y := int(buffer[i*numChannels+channel]*mult+ImageHeight/2) + ImageHeight * channel
outimage.Set(i, y, color.Black)
outimage.Set(i, y+1, color.Black)
}
}
png.Encode(imageFile, outimage)
}
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