filter: change num to var in saveFrame(), move helper function to bottom, for loop to range

filter/basic.go

@@ -142,7 +142,7 @@ func (bf *Basic) Write(f []byte) (int, error) {
 	if bf.debug {
 		err := bf.saveFrame()
 		if err != nil {
-			return len(f), err
+			return len(f), fmt.Errorf("image can't be encoded for debug video: %w", err)
 		}
 	}
 
@@ -155,19 +155,9 @@ func (bf *Basic) Write(f []byte) (int, error) {
 	return bf.dst.Write(f)
 }
 
-func absDiff(a, b uint32) int {
-	c := int(a) - int(b)
-	if c < 0 {
-		return -c
-	} else {
-		return c
-	}
-
-}
-
 // Go routine for one row of the image to be processed
 func (bf *Basic) process(j int, wg *sync.WaitGroup) {
-	for i := 0; i < bf.w; i++ {
+	for i, _ := range bf.bg[j] {
 		n := bf.img.At(i, j)
 		r, b, g, _ := n.RGBA()
 
@@ -207,12 +197,21 @@ func (bf *Basic) saveFrame() error {
 		Dot:  fixed.P(20, 30),
 	}
 	var s string
-	if bf.motion > 1000 {
+	if bf.motion > bf.pix {
 		s = strconv.Itoa(bf.motion) + " Motion"
 	} else {
 		s = strconv.Itoa(bf.motion)
 	}
 	d.DrawString(s)
-	err := jpeg.Encode(bf.file, bf.bwImg, nil)
+	return jpeg.Encode(bf.file, bf.bwImg, nil)
-	return err
+}
+
+func absDiff(a, b uint32) int {
+	c := int(a) - int(b)
+	if c < 0 {
+		return -c
+	} else {
+		return c
+	}
+
 }