Save IR plot in same directory as IR file with matching filename

pkg/convolve/convolve.go

@@ -6,6 +6,7 @@ import (
 	"math"
 	"math/cmplx"
 	"os"
+	"strings"
 
 	"image/png"
 
@@ -642,8 +643,13 @@ func PlotIR(ir []float64, sampleRate int, irFileName string) error {
 	p2.Draw(canvases[1][0])
 	dc.DrawImage(vg.Rectangle{Min: vg.Point{X: 0, Y: 0}, Max: vg.Point{X: width, Y: height}}, imgPlots.Image())
 
-	// Save as PNG
-	f, err = os.Create("ir_plot.png")
+	// Save as PNG in the same directory as the IR file
+	irDir := filepath.Dir(irFileName)
+	irBase := filepath.Base(irFileName)
+	irNameWithoutExt := strings.TrimSuffix(irBase, filepath.Ext(irBase))
+	plotFileName := filepath.Join(irDir, irNameWithoutExt+".png")
+
+	f, err = os.Create(plotFileName)
 	if err != nil {
 		return err
 	}