improved corner detection in transform function, fixed some comments

turbidity/results.go

@@ -29,14 +29,14 @@ package main
 
 import "fmt"
 
-// Struct to hold the results of the turbidity sensor.
+// Results holds the results of the turbidity sensor.
 type Results struct {
 	Turbidity  []float64
 	Saturation []float64
 	Contrast   []float64
 }
 
-// Results constructor
+// NewResults constructs the results object.
 func NewResults(n int) (*Results, error) {
 
 	if n <= 0 {
@@ -51,7 +51,7 @@ func NewResults(n int) (*Results, error) {
 	return r, nil
 }
 
-// Update results to add new values at specified index.
+// Update adds new values to slice at specified index.
 func (r *Results) Update(newSat, newCont, newTurb float64, index int) {
 	r.Saturation[index] = newSat
 	r.Contrast[index] = newCont

turbidity/turbidity.go

@@ -40,24 +40,37 @@ import (
 // TurbiditySensor is a software based turbidity sensor that uses CV to determine saturation and constrast level
 // of a chessboard-like target submerged in water that can be correlated to turbidity/visibility values.
 type TurbiditySensor struct {
-	template, standard      gocv.Mat
+	template, templateCorners gocv.Mat
+	standard, standardCorners gocv.Mat
 	k1, k2, sobelFilterSize   int
 	scale, alpha              float64
 }
 
-// Turbidity sensor constructor.
+// NewTurbiditySensor constructor for a turbidity sensor.
 func NewTurbiditySensor(template, standard gocv.Mat, k1, k2, sobelFilterSize int, scale, alpha float64) (*TurbiditySensor, error) {
 	ts := new(TurbiditySensor)
+	templateCorners := gocv.NewMat()
+	standardCorners := gocv.NewMat()
 
+	// Validate template image is not empty and has valid corners.
 	if template.Empty() {
 		return nil, errors.New("template image is empty.")
 	}
+	if !gocv.FindChessboardCorners(template, image.Pt(3, 3), &templateCorners, gocv.CalibCBNormalizeImage) {
+		return nil, errors.New("could not find corners in template image")
+	}
 	ts.template = template
+	ts.templateCorners = templateCorners
 
+	// Validate standard image is not empty and has valid corners.
 	if standard.Empty() {
 		return nil, errors.New("standard image is empty.")
 	}
+	if !gocv.FindChessboardCorners(standard, image.Pt(3, 3), &standardCorners, gocv.CalibCBNormalizeImage) {
+		return nil, errors.New("could not find corners in standard image")
+	}
 	ts.standard = standard
+	ts.standardCorners = standardCorners
 
 	ts.k1, ts.k2, ts.sobelFilterSize = k1, k2, sobelFilterSize
 	ts.alpha, ts.scale = alpha, scale
@@ -130,6 +143,7 @@ func (ts TurbiditySensor) EvaluateImage(img, edge gocv.Mat) (float64, float64, e
 	return sharpness, contrast, nil
 }
 
+// minMax returns the max and min pixel values of an image block.
 func (ts TurbiditySensor) minMax(img gocv.Mat, xStart, yStart, xEnd, yEnd int) (float64, float64) {
 	max := -math.MaxFloat64
 	min := math.MaxFloat64
@@ -150,7 +164,7 @@ func (ts TurbiditySensor) minMax(img gocv.Mat, xStart, yStart, xEnd, yEnd int) (
 	return max, min
 }
 
-// Evaluate a block within an image and return the value to be added to the sharpness result.
+// evaluateBlockEME will evaluate an image block and return the value to be added to the sharpness result.
 func (ts TurbiditySensor) evaluateBlockEME(img gocv.Mat, xStart, yStart, xEnd, yEnd int) float64 {
 	max, min := ts.minMax(img, xStart, yStart, xEnd, yEnd)
 
@@ -161,7 +175,7 @@ func (ts TurbiditySensor) evaluateBlockEME(img gocv.Mat, xStart, yStart, xEnd, y
 	return 0.0
 }
 
-// Evaluate a block within an image and return the value to be added to the contrast result.
+// evaluateBlockAMEE will evaluate an image block and return the value to be added to the contrast result.
 func (ts TurbiditySensor) evaluateBlockAMEE(img gocv.Mat, xStart, yStart, xEnd, yEnd int) float64 {
 	max, min := ts.minMax(img, xStart, yStart, xEnd, yEnd)
 
@@ -177,29 +191,19 @@ func (ts TurbiditySensor) evaluateBlockAMEE(img gocv.Mat, xStart, yStart, xEnd,
 func (ts TurbiditySensor) transform(img gocv.Mat) (gocv.Mat, error) {
 	out := gocv.NewMat()
 	mask := gocv.NewMat()
-	corners_img := gocv.NewMat()
-	corners_template := gocv.NewMat()
+	imgCorners := gocv.NewMat()
 
 	// Check image is valid.
 	if img.Empty() {
 		return out, errors.New("image is empty, cannot transform")
 	}
-
-	// Find corners in image.
-	if !gocv.FindChessboardCorners(img, image.Pt(3, 3), &corners_img, gocv.CalibCBNormalizeImage) {
-		// Apply default if transformation fails.
-		if !gocv.FindChessboardCorners(ts.standard, image.Pt(3, 3), &corners_img, gocv.CalibCBNormalizeImage) {
-			return out, errors.New("Could not find corners in default image")
-		}
-	}
-
-	// Find corners in template.
-	if !gocv.FindChessboardCorners(ts.template, image.Pt(3, 3), &corners_template, gocv.CalibCBNormalizeImage) {
-		return out, errors.New("Could not find corners in template")
+	// Check image for corners, if non can be found corners will be set to default value.
+	if !gocv.FindChessboardCorners(img, image.Pt(3, 3), &imgCorners, gocv.CalibCBFastCheck) {
+		imgCorners = ts.standardCorners
 	}
 
 	// Find and apply transformation.
-	H := gocv.FindHomography(corners_img, &corners_template, gocv.HomograpyMethodRANSAC, 3.0, &mask, 2000, 0.995)
+	H := gocv.FindHomography(imgCorners, &ts.templateCorners, gocv.HomograpyMethodRANSAC, 3.0, &mask, 2000, 0.995)
 	gocv.WarpPerspective(img, &out, H, image.Pt(ts.template.Rows(), ts.template.Cols()))
 
 	return out, nil

turbidity/turbidity_test.go

@@ -59,7 +59,7 @@ func TestImages(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	// Create results
+	// Create results.
 	results, err := NewResults(nImages)
 	if err != nil {
 		t.Fatal(err)