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increase vertical resolution of waveform img, calculate with less casting

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This commit is contained in:
Drew Weymouth
2025-07-30 17:36:56 -07:00
parent 9a1325b92d
commit 8f50e1087b
1 changed files with 19 additions and 22 deletions
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backend/waveformimage.go
+19 -22
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@@ -28,7 +28,7 @@ type WaveformImageGenerator struct {
type WaveformImage = image.NRGBA
func NewWaveformImage() *WaveformImage {
return image.NewNRGBA(image.Rect(0, 0, 1024, 32))
return image.NewNRGBA(image.Rect(0, 0, 1024, 48))
}
type WaveformImageJob struct {
@@ -198,9 +198,9 @@ type waveformData struct {
}
func generateWaveformImage(ctx context.Context, data *waveformData, job *WaveformImageJob) {
centerY := job.img.Rect.Dy() / 2 // 16
top := centerY - 1
bottom := centerY
centerY := job.img.Rect.Dy() / 2 // 24
top := centerY - 1 // 23
bottom := centerY // 24
opaqueColor := color.NRGBA{R: 255, G: 255, B: 255, A: 255}
translucentColor := color.NRGBA{R: 255, G: 255, B: 255, A: 128}
@@ -216,26 +216,23 @@ func generateWaveformImage(ctx context.Context, data *waveformData, job *Wavefor
time.Sleep(50 * time.Millisecond)
}
rms := float64(data.RMS[x]) / 255.0
peak := float64(data.Peak[x]) / 255.0
rmsPixels := int(rms * 16)
peakPixels := int((peak - rms) * 16)
rmsPixels := int(data.RMS[x]) * centerY / 255
peakPixels := int(data.Peak[x]) * centerY / 255
// Always draw at least 2 center pixels
setPixel(job.img, x, top, opaqueColor)
setPixel(job.img, x, bottom, opaqueColor)
// Draw RMS pixels (solid)
for i := 1; i <= rmsPixels; i++ {
for i := 1; i < rmsPixels; i++ {
setPixel(job.img, x, top-i, opaqueColor)
setPixel(job.img, x, bottom+i, opaqueColor)
}
// Draw Peak extension (translucent)
for i := 1; i <= peakPixels; i++ {
setPixel(job.img, x, top-rmsPixels-i, translucentColor)
setPixel(job.img, x, bottom+rmsPixels+i, translucentColor)
for i := max(1, rmsPixels); i < peakPixels; i++ {
setPixel(job.img, x, top-i, translucentColor)
setPixel(job.img, x, bottom+i, translucentColor)
}
job.progress = x + 1
}
@@ -266,7 +263,7 @@ func analyzeWavFile(ctx context.Context, transcodeFile string, data *waveformDat
buf := &audio.IntBuffer{Data: make([]int, 4096)}
curChunk := 0
chunkSamples := make([]float32, 0, samplesPerChunk)
chunkSamples := make([]float64, 0, samplesPerChunk)
bytesPerSample := int64(2 * format.NumChannels) // 16-bit = 2 bytes per channel
// file read loop
@@ -324,14 +321,14 @@ func analyzeWavFile(ctx context.Context, transcodeFile string, data *waveformDat
// Process samples
for i := 0; i < n; i++ {
sample := float32(buf.Data[i]) / float32(1<<15) // Normalize to [-1, 1]
sample := float64(buf.Data[i]) / float64(1<<15) // Normalize to [-1, 1]
chunkSamples = append(chunkSamples, sample)
if len(chunkSamples) >= samplesPerChunk {
if curChunk < 1024 {
peak, rms := computePeakAndRMS(chunkSamples)
data.Peak[curChunk] = float32ToByte(peak)
data.RMS[curChunk] = float32ToByte(rms)
data.Peak[curChunk] = float64ToByte(peak)
data.RMS[curChunk] = float64ToByte(rms)
}
curChunk++
data.progress = curChunk
@@ -346,8 +343,8 @@ func analyzeWavFile(ctx context.Context, transcodeFile string, data *waveformDat
// analyze the last chunk if it's partially filled with samples
if curChunk < 1024 && len(chunkSamples) > 0 {
peak, rms := computePeakAndRMS(chunkSamples)
data.Peak[curChunk] = float32ToByte(peak)
data.RMS[curChunk] = float32ToByte(rms)
data.Peak[curChunk] = float64ToByte(peak)
data.RMS[curChunk] = float64ToByte(rms)
data.progress = curChunk + 1
}
@@ -361,7 +358,7 @@ func (j *WaveformImageJob) setError(err error) {
j.err = err
}
func computePeakAndRMS(chunk []float32) (peak float32, rms float32) {
func computePeakAndRMS(chunk []float64) (peak float64, rms float64) {
var sumSquares float64
peak = 0.0
for _, v := range chunk {
@@ -372,11 +369,11 @@ func computePeakAndRMS(chunk []float32) (peak float32, rms float32) {
}
sumSquares += float64(v * v)
}
rms = float32(math.Sqrt(sumSquares / float64(len(chunk))))
rms = math.Sqrt(sumSquares / float64(len(chunk)))
return
}
func float32ToByte(val float32) byte {
func float64ToByte(val float64) byte {
if val > 1.0 {
val = 1.0
}