Add NativeFrame GetImage conversion test, fix row selection in conversion.

pkg/frame/native.go

@@ -35,7 +35,7 @@ func (n *NativeFrame) GetEncapsulatedFrame() (*EncapsulatedFrame, error) {
 func (n *NativeFrame) GetImage() (image.Image, error) {
 	i := image.NewGray16(image.Rect(0, 0, n.Cols, n.Rows))
 	for j := 0; j < len(n.Data); j++ {
-		i.SetGray16(j%n.Cols, j/n.Rows, color.Gray16{Y: uint16(n.Data[j][0])}) // for now, assume we're not overflowing uint16, assume gray image
+		i.SetGray16(j%n.Cols, j/n.Cols, color.Gray16{Y: uint16(n.Data[j][0])}) // for now, assume we're not overflowing uint16, assume gray image
 	}
 	return i, nil
 }

pkg/frame/native_test.go

@@ -0,0 +1,93 @@
+package frame_test
+
+import (
+	"image"
+	"testing"
+
+	"github.com/suyashkumar/dicom/pkg/frame"
+)
+
+// point represents a 2D point for testing.
+type point struct {
+	x int
+	y int
+}
+
+func TestNativeFrame_GetImage(t *testing.T) {
+	cases := []struct {
+		Name        string
+		NativeFrame frame.NativeFrame
+		SetPoints   []point
+	}{
+		{
+			Name: "Square",
+			NativeFrame: frame.NativeFrame{
+				Rows: 2,
+				Cols: 2,
+				Data: [][]int{{0}, {0}, {1}, {0}},
+			},
+			SetPoints: []point{{0, 1}},
+		},
+		{
+			Name: "Rectangle",
+			NativeFrame: frame.NativeFrame{
+				Rows: 3,
+				Cols: 2,
+				Data: [][]int{{0}, {0}, {0}, {0}, {1}, {0}},
+			},
+			SetPoints: []point{{0, 2}},
+		},
+		{
+			Name: "Rectangle - multiple points",
+			NativeFrame: frame.NativeFrame{
+				Rows: 5,
+				Cols: 3,
+				Data: [][]int{{0}, {0}, {0}, {0}, {1}, {1}, {0}, {0}, {0}, {0}, {1}, {0}, {0}, {0}, {0}},
+			},
+			SetPoints: []point{{1, 1}, {2, 1}, {1, 3}},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.Name, func(t *testing.T) {
+			img, err := tc.NativeFrame.GetImage()
+			if err != nil {
+				t.Fatalf("GetImage(%v) got unexpected error: %v", tc.NativeFrame, err)
+			}
+			imgGray, ok := img.(*image.Gray16)
+			if !ok {
+				t.Fatalf("GetImage(%v) did not return an image convertible to Gray16", tc.NativeFrame)
+			}
+
+			// Check that all pixels are zero except at the
+			// (ExpectedSetPointX, ExpectedSetPointY) point.
+			for x := 0; x < tc.NativeFrame.Cols; x++ {
+				for y := 0; y < tc.NativeFrame.Rows; y++ {
+					currValue := imgGray.Gray16At(x, y).Y
+					if within(point{x, y}, tc.SetPoints) {
+						if currValue != 1 {
+							t.Errorf("GetImage(%v), unexpected value at set point. got: %v, want: %v", tc.NativeFrame, currValue, 1)
+						}
+						continue
+					}
+
+					if currValue != 0 {
+						t.Errorf("GetImage(%v), unexpected value outside of set point. At (%d, %d) got: %v, want: %v", tc.NativeFrame, x, y, currValue, 0)
+					}
+
+				}
+			}
+		})
+
+	}
+}
+
+// within returns true if pt is in the []point
+func within(pt point, set []point) bool {
+	for _, item := range set {
+		if pt.x == item.x && pt.y == item.y {
+			return true
+		}
+	}
+	return false
+}