add Min function

vips/arithmetic.c

@@ -81,3 +81,7 @@ int absOp(VipsImage *img, VipsImage **out) {
 int project(VipsImage *in, VipsImage **col, VipsImage **row) {
   return vips_project(in, col, row, NULL);
 }
+
+int minOp(VipsImage *in, double *out, int *x, int *y, int size) {
+  return vips_min(in, out, "x", x, "y", y, "size", size, NULL);
+}

vips/arithmetic.go

@@ -208,3 +208,16 @@ func vipsProject(in *C.VipsImage) (*C.VipsImage, *C.VipsImage, error) {
 	}
 	return col, row, nil
 }
+
+// https://www.libvips.org/API/current/libvips-arithmetic.html#vips-min
+func vipsMin(in *C.VipsImage) (float64, int, int, error) {
+	incOpCounter("min")
+	var out C.double
+	var x, y C.int
+
+	if err := C.minOp(in, &out, &x, &y, C.int(1)); err != 0 {
+		return 0, 0, 0, handleVipsError()
+	}
+
+	return float64(out), int(x), int(y), nil
+}

vips/arithmetic.h

@@ -21,3 +21,4 @@ int hist_entropy(VipsImage *in, double *out);
 int subtract(VipsImage *in1, VipsImage *in2, VipsImage **out);
 int absOp(VipsImage *img, VipsImage **out);
 int project(VipsImage *in, VipsImage **col, VipsImage **row);
+int minOp(VipsImage *in, double *out, int *x, int *y, int size);

vips/image.go

@@ -1824,6 +1824,11 @@ func (r *ImageRef) Project() (*ImageRef, *ImageRef, error) {
 	return newImageRef(col, r.format, r.originalFormat, nil), newImageRef(row, r.format, r.originalFormat, nil), nil
 }
 
+// Min finds the minimum value in an image.
+func (r *ImageRef) Min() (float64, int, int, error) {
+	return vipsMin(r.image)
+}
+
 // Rank does rank filtering on an image. A window of size width by height is passed over the image.
 // At each position, the pixels inside the window are sorted into ascending order and the pixel at position
 // index is output. index numbers from 0.

vips/image_test.go

@@ -1212,6 +1212,9 @@ func TestImageRef_ArithmeticOperation(t *testing.T) {
 	orgWidth := image.Width()
 	orgHeight := image.Height()
 
+	_, _, _, err = image.Min()
+	require.NoError(t, err)
+
 	err = image2.Abs()
 	require.NoError(t, err)