Reorganise image manipulation to separate integral image parts

Also unify everything else under preproc/

Note that the UsefulImg interface should be used by the main
functions, to simplify things, but this hasn't been done yet.

1 files changed, 62 insertions, 0 deletions

diff --git a/preproc/sauvola_test.go b/preproc/sauvola_test.go
new file mode 100644
index 0000000..1397a4f
--- /dev/null
+++ b/preproc/sauvola_test.go
@@ -0,0 +1,62 @@
+package preproc
+
+import (
+	"fmt"
+	"image"
+	"image/png"
+	"os"
+	"testing"
+)
+
+func TestBinarization(t *testing.T) {
+	cases := []struct {
+		name string
+		orig string
+		golden string
+		ksize float64
+		wsize int
+	}{
+		{"integralsauvola", "testdata/pg1.png", "testdata/pg1_integralsauvola_k0.5_w41.png", 0.5, 41},
+		{"integralsauvola", "testdata/pg1.png", "testdata/pg1_integralsauvola_k0.5_w19.png", 0.5, 19},
+		{"integralsauvola", "testdata/pg1.png", "testdata/pg1_integralsauvola_k0.3_w19.png", 0.3, 19},
+		{"sauvola", "testdata/pg1.png", "testdata/pg1_sauvola_k0.5_w41.png", 0.5, 41},
+		{"sauvola", "testdata/pg1.png", "testdata/pg1_sauvola_k0.5_w19.png", 0.5, 19},
+		{"sauvola", "testdata/pg1.png", "testdata/pg1_sauvola_k0.3_w19.png", 0.3, 19},
+	}
+
+	for _, c := range cases {
+		t.Run(fmt.Sprintf("%s_%0.1f_%d", c.name, c.ksize, c.wsize), func(t *testing.T) {
+			var actual *image.Gray
+			orig, err := decode(c.orig)
+			if err != nil {
+				t.Fatalf("Could not open file %s: %v\n", c.orig, err)
+			}
+			switch c.name {
+			case "integralsauvola":
+				actual = IntegralSauvola(orig, c.ksize, c.wsize)
+			case "sauvola":
+				actual = Sauvola(orig, c.ksize, c.wsize)
+			default:
+				t.Fatalf("No method %s\n", c.name)
+			}
+			if *update {
+				f, err := os.Create(c.golden)
+				defer f.Close()
+				if err != nil {
+					t.Fatalf("Could not open file %s to update: %v\n", c.golden, err)
+				}
+				err = png.Encode(f, actual)
+				if err != nil {
+					t.Fatalf("Could not encode update of %s: %v\n", c.golden, err)
+				}
+			}
+			golden, err := decode(c.golden)
+			if err != nil {
+				t.Fatalf("Could not open file %s: %v\n", c.golden, err)
+			}
+			if ! imgsequal(golden, actual) {
+				t.Errorf("Binarized %s differs to %s\n", c.orig, c.golden)
+			}
+		})
+	}
+}