--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pkg/octree/classbreaks.go	Fri Jul 05 11:29:10 2019 +0200
@@ -0,0 +1,126 @@
+// This is Free Software under GNU Affero General Public License v >= 3.0
+// without warranty, see README.md and license for details.
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// License-Filename: LICENSES/AGPL-3.0.txt
+//
+// Copyright (C) 2019 by via donau
+//   – Österreichische Wasserstraßen-Gesellschaft mbH
+// Software engineering by Intevation GmbH
+//
+// Author(s):
+//  * Sascha L. Teichmann <sascha.teichmann@intevation.de>
+
+package octree
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"math"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+const (
+	selectClassBreaksSQL = `
+SELECT config_val FROM sys_admin.system_config
+WHERE config_key = $1`
+)
+
+func SampleDiffHeights(min, max, step float64) []float64 {
+	var heights []float64
+	switch {
+	case min >= 0: // All values positive.
+		for v := 0.0; v <= max; v += step {
+			if v >= min {
+				heights = append(heights, v)
+			}
+		}
+	case max <= 0: // All values negative.
+		for v := 0.0; v >= min; v -= step {
+			if v <= max {
+				heights = append(heights, v)
+			}
+		}
+	default: // Positive and negative.
+		for v := step; v <= max; v += step {
+			heights = append(heights, v)
+		}
+		for i, j := 0, len(heights)-1; i < j; i, j = i+1, j-1 {
+			heights[i], heights[j] = heights[j], heights[i]
+		}
+		for v := 0.0; v >= min; v -= step {
+			heights = append(heights, v)
+		}
+	}
+	return heights
+}
+
+func LoadClassBreaks(ctx context.Context, tx *sql.Tx, key string) ([]float64, error) {
+
+	var config sql.NullString
+
+	err := tx.QueryRowContext(ctx, selectClassBreaksSQL, key).Scan(&config)
+
+	switch {
+	case err == sql.ErrNoRows:
+		return nil, nil
+	case err != nil:
+		return nil, err
+	case !config.Valid:
+		return nil, errors.New("Invalid config string")
+	}
+
+	parts := strings.Split(config.String, ",")
+	classes := make([]float64, 0, len(parts))
+	for _, part := range parts {
+		if idx := strings.IndexRune(part, ':'); idx >= 0 {
+			part = part[idx+1:]
+		}
+		if part = strings.TrimSpace(part); part == "" {
+			continue
+		}
+		v, err := strconv.ParseFloat(part, 64)
+		if err != nil {
+			return nil, err
+		}
+		classes = append(classes, v)
+	}
+
+	sort.Float64s(classes)
+	return classes, nil
+}
+
+func InBetweenClassBreaks(cbs []float64, min float64, steps int) []float64 {
+	if len(cbs) < 2 || steps < 2 {
+		return cbs
+	}
+
+	out := make([]float64, 1, len(cbs)*steps)
+
+	out[0] = cbs[0]
+
+	_1steps := 1 / float64(steps)
+
+	for i := 1; i < len(cbs); i++ {
+		last, curr := cbs[i-1], cbs[i]
+
+		// Gap already too small -> proceed with next gap.
+		diff := curr - last
+		if math.Abs(diff) < min {
+			out = append(out, curr)
+			continue
+		}
+
+		delta := diff * _1steps
+		for p := last + delta; p < curr; p += delta {
+			out = append(out, p)
+		}
+
+		out = append(out, curr)
+	}
+
+	return out
+}

--- a/pkg/octree/contours.go	Fri Jul 05 10:31:23 2019 +0200
+++ b/pkg/octree/contours.go	Fri Jul 05 11:29:10 2019 +0200
@@ -19,35 +19,6 @@
 	"sync"
 )
 
-func SampleDiffHeights(min, max, step float64) []float64 {
-	var heights []float64
-	switch {
-	case min >= 0: // All values positive.
-		for v := 0.0; v <= max; v += step {
-			if v >= min {
-				heights = append(heights, v)
-			}
-		}
-	case max <= 0: // All values negative.
-		for v := 0.0; v >= min; v -= step {
-			if v <= max {
-				heights = append(heights, v)
-			}
-		}
-	default: // Positive and negative.
-		for v := step; v <= max; v += step {
-			heights = append(heights, v)
-		}
-		for i, j := 0, len(heights)-1; i < j; i, j = i+1, j-1 {
-			heights[i], heights[j] = heights[j], heights[i]
-		}
-		for v := 0.0; v >= min; v -= step {
-			heights = append(heights, v)
-		}
-	}
-	return heights
-}
-
 // ContourResult stores an calculated iso line for a given height.
 // Is used as a future variable in the concurrent iso line calculation.
 type ContourResult struct {