Fix threshold on sub-images (#6)

Ernyoke · Jul 27, 2024 · 461615a · 461615a
1 parent d5d9042
commit 461615a
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Showing 7 changed files with 32 additions and 5 deletions.
diff --git a/res/threshold/otsuThreshBinCropped.jpg b/res/threshold/otsuThreshBinCropped.jpg
diff --git a/res/threshold/otsuThreshBinInvCropped.jpg b/res/threshold/otsuThreshBinInvCropped.jpg
diff --git a/res/threshold/otsuThreshToZeroCropped.jpg b/res/threshold/otsuThreshToZeroCropped.jpg
diff --git a/res/threshold/otsuThreshToZeroInvCropped.jpg b/res/threshold/otsuThreshToZeroInvCropped.jpg
diff --git a/res/threshold/otsuThreshTruncCropped.jpg b/res/threshold/otsuThreshTruncCropped.jpg
diff --git a/threshold/threshold.go b/threshold/threshold.go
@@ -2,10 +2,11 @@ package threshold
 
 import (
 	"errors"
-	"github.com/ernyoke/imger/histogram"
-	"github.com/ernyoke/imger/utils"
 	"image"
 	"image/color"
+
+	"github.com/ernyoke/imger/histogram"
+	"github.com/ernyoke/imger/utils"
 )
 
 // Method is an enum type for global threshold methods
@@ -176,17 +177,19 @@ func OtsuThreshold(img *image.Gray, method Method) (*image.Gray, error) {
 func threshold(img *image.Gray, setPixel func(*image.Gray, int, int)) *image.Gray {
 	size := img.Bounds().Size()
 	gray := image.NewGray(img.Bounds())
+	offset := img.Bounds().Min
 	utils.ParallelForEachPixel(size, func(x, y int) {
-		setPixel(gray, x, y)
+		setPixel(gray, x+offset.X, y+offset.Y)
 	})
 	return gray
 }
 
 func threshold16(img *image.Gray16, setPixel16 func(*image.Gray16, int, int)) *image.Gray16 {
 	size := img.Bounds().Size()
 	gray := image.NewGray16(img.Bounds())
+	offset := img.Bounds().Min
 	utils.ParallelForEachPixel(size, func(x, y int) {
-		setPixel16(gray, x, y)
+		setPixel16(gray, x+offset.X, y+offset.Y)
 	})
 	return gray
 }

diff --git a/threshold/threshold_test.go b/threshold/threshold_test.go
@@ -1,9 +1,11 @@
 package threshold
 
 import (
-	"github.com/ernyoke/imger/imgio"
+	"fmt"
 	"image"
 	"testing"
+
+	"github.com/ernyoke/imger/imgio"
 )
 
 // -----------------------------Acceptance tests------------------------------------
@@ -107,4 +109,26 @@ func Test_Acceptance_OtsuThreshold(t *testing.T) {
 	tearDownTestCase(t, thresh, "../res/threshold/otsuThreshBin.jpg")
 }
 
+func Test_Acceptance_OtsuThreshold_Cropped(t *testing.T) {
+	thresholdMethods := map[string]Method{
+		"Bin":       ThreshBinary,
+		"BinInv":    ThreshBinaryInv,
+		"Trunc":     ThreshTrunc,
+		"ToZero":    ThreshToZero,
+		"ToZeroInv": ThreshToZeroInv,
+	}
+
+	for name, meth := range thresholdMethods {
+		t.Run(name, func(t *testing.T) {
+			gray := setupTestCaseOtsu(t)
+			cropped := gray.SubImage(image.Rect(100, 100, gray.Bounds().Max.X-100, gray.Bounds().Max.Y-100))
+			thresh, err := OtsuThreshold(cropped.(*image.Gray), meth)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			tearDownTestCase(t, thresh, fmt.Sprintf("../res/threshold/otsuThresh%sCropped.jpg", name))
+		})
+	}
+}
+
 //---------------------------------------------------------------------------------