Add support for 45° rotation.

options.go

@@ -57,12 +57,20 @@ type Angle int
 const (
 	// D0 represents the rotation angle 0 degrees.
 	D0 Angle = 0
+	// D45 represents the rotation angle 90 degrees.
+	D45 Angle = 45
 	// D90 represents the rotation angle 90 degrees.
 	D90 Angle = 90
+	// D135 represents the rotation angle 90 degrees.
+	D135 Angle = 135
 	// D180 represents the rotation angle 180 degrees.
 	D180 Angle = 180
+	// D180 represents the rotation angle 180 degrees.
+	D235 Angle = 235
 	// D270 represents the rotation angle 270 degrees.
 	D270 Angle = 270
+	// D315 represents the rotation angle 180 degrees.
+	D315 Angle = 315
 )
 
 // Direction represents the image direction value.

vips.h

@@ -121,15 +121,31 @@ int
 vips_rotate(VipsImage *in, VipsImage **out, int angle) {
 	int rotate = VIPS_ANGLE_D0;
 
-	if (angle == 90) {
+	angle %= 360;
+
+	if (angle == 45) {
+		rotate = VIPS_ANGLE45_D45;
+	} else if (angle == 90) {
 		rotate = VIPS_ANGLE_D90;
+	} else if (angle == 135) {
+		rotate = VIPS_ANGLE45_D135;
 	} else if (angle == 180) {
 		rotate = VIPS_ANGLE_D180;
+	} else if (angle == 225) {
+		rotate = VIPS_ANGLE45_D225;
 	} else if (angle == 270) {
 		rotate = VIPS_ANGLE_D270;
+	} else if (angle == 315) {
+		rotate = VIPS_ANGLE45_D315;
+	} else {
+		angle = 0;
 	}
 
+	if (angle > 0 && angle % 90 != 0) {
+		return vips_rot45(in, out, "angle", rotate, NULL);
+	} else {
 		return vips_rot(in, out, rotate, NULL);
+	}
 }
 
 int

vips_test.go

@@ -42,17 +42,27 @@ func TestVipsSave(t *testing.T) {
 }
 
 func TestVipsRotate(t *testing.T) {
-	image, _, _ := vipsRead(readImage("test.jpg"))
+	files := []struct {
+		name   string
+		rotate Angle
+	}{
+		{"test.jpg", D90},
+		{"test_square.jpg", D45},
+	}
 
-	newImg, err := vipsRotate(image, D90)
+	for _, file := range files {
+		image, _, _ := vipsRead(readImage(file.name))
+
+		newImg, err := vipsRotate(image, file.rotate)
 		if err != nil {
-		t.Fatal("Cannot save the image")
+			t.Fatal("Cannot rotate the image")
 		}
 
 		buf, _ := vipsSave(newImg, vipsSaveOptions{Quality: 95})
 		if len(buf) == 0 {
 			t.Fatal("Empty image")
 		}
+	}
 }
 
 func TestVipsZoom(t *testing.T) {