added DEMProcessing utility func

testdata/demproc_colors.txt

@@ -0,0 +1,6 @@
+2000   white
+100%   235:220:175
+50%   190 185 135
+4    240 250 150
+0      50  180  50
+nv     0   0   0   0

utilities.go

@@ -163,5 +163,40 @@ func Rasterize(dstDS string, sourceDS Dataset, options []string) (Dataset, error
 		return Dataset{}, fmt.Errorf("rasterize failed with code %d", cerr)
 	}
 	return Dataset{ds}, nil
+}
+
+func DEMProcessing(dstDS string, sourceDS Dataset, processing string, colorFileName string, options []string) (Dataset, error) {
+	if dstDS == "" {
+		dstDS = "MEM:::"
+		if !stringArrayContains(options, "-f") {
+			options = append([]string{"-of", "MEM"}, options...)
+		}
+	}
+	length := len(options)
+	opts := make([]*C.char, length+1)
+	for i := 0; i < length; i++ {
+		opts[i] = C.CString(options[i])
+		defer C.free(unsafe.Pointer(opts[i]))
+	}
+	opts[length] = (*C.char)(unsafe.Pointer(nil))
+	demprocessingopts := C.GDALDEMProcessingOptionsNew(
+		(**C.char)(unsafe.Pointer(&opts[0])),
+		(*C.GDALDEMProcessingOptionsForBinary)(unsafe.Pointer(nil)))
+	defer C.GDALDEMProcessingOptionsFree(demprocessingopts)
+
+	var cerr C.int
+	cdstDS := C.CString(dstDS)
+	defer C.free(unsafe.Pointer(cdstDS))
 
+	cprocessing := C.CString(processing)
+	defer C.free(unsafe.Pointer(cprocessing))
+	ds := C.GDALDEMProcessing(cdstDS,
+		sourceDS.cval,
+		cprocessing,
+		demprocessingopts,
+		&cerr)
+	if cerr != 0 {
+		return Dataset{}, fmt.Errorf("demprocessing failed with code %d", cerr)
+	}
+	return Dataset{ds}, nil
 }

utilities_test.go

@@ -83,3 +83,24 @@ func TestTranslate(t *testing.T) {
 	}
 	dstDS.Close()
 }
+
+func TestDEMProcessing(t *testing.T) {
+	srcDS, err := Open("testdata/demproc.tif", ReadOnly)
+	if err != nil {
+		t.Errorf("Open: %v", err)
+	}
+
+	opts := []string{"-of", "GTiff"}
+
+	dstDS, err := DEMProcessing("/tmp/demproc_output.tif", srcDS, "color-relief", "testdata/demproc_colors.txt", opts)
+	if err != nil {
+		t.Errorf("DEMProcessing: %v", err)
+	}
+	dstDS.Close()
+
+	dstDS, err = Open("/tmp/demproc_output.tif", ReadOnly)
+	if err != nil {
+		t.Errorf("Open after raster DEM Processing: %v", err)
+	}
+	dstDS.Close()
+}