--- a/pkg/common/linear.go	Mon Nov 18 16:38:28 2019 +0100
+++ b/pkg/common/linear.go	Tue Nov 19 12:45:52 2019 +0100
@@ -10,6 +10,7 @@
 //
 // Author(s):
 //  * Sascha L. Teichmann <sascha.teichmann@intevation.de>
+
 package common
 
 // Linear constructs a function which maps x1 to y1 and x2 to y2.

--- a/pkg/models/colors.go	Mon Nov 18 16:38:28 2019 +0100
+++ b/pkg/models/colors.go	Tue Nov 19 12:45:52 2019 +0100
@@ -24,13 +24,18 @@
 )
 
 type (
+	// ColorValue models a tuple of a floating point value and a color.
 	ColorValue struct {
 		Value float64
 		Color color.RGBA
 	}
 
+	// ColorValues are a list of color values.
+	// Colors between the given ones are linear interpolated.
 	ColorValues []ColorValue
 
+	// ClassBreak is a potential open interval of values associated
+	// with a color.
 	ClassBreak struct {
 		High    float64
 		HasHigh bool
@@ -40,6 +45,8 @@
 	}
 )
 
+// Color gives a HTML compatible string representation of the color
+// of the class break.
 func (cb *ClassBreak) Color() string {
 	return fmt.Sprintf("#%02x%02x%02x",
 		cb.Col.R,
@@ -48,6 +55,8 @@
 	)
 }
 
+// ClassBreaks converts a list of colors to a list of class breaks.
+// The first an the last class break are open on the respective end.
 func (cc ColorValues) ClassBreaks() []ClassBreak {
 
 	cbs := make([]ClassBreak, len(cc), len(cc)+1)
@@ -71,6 +80,7 @@
 	return cbs
 }
 
+// Heights extracts the values friom the color value pairs.
 func (cc ColorValues) Heights() []float64 {
 	heights := make([]float64, len(cc))
 	for i := range cc {
@@ -79,6 +89,9 @@
 	return heights
 }
 
+// Clip does the same as Interpolate
+// but if the value is out of bounds the value of the nearest border
+// is returned.
 func (cc ColorValues) Clip(v float64) color.RGBA {
 	if len(cc) == 0 {
 		return color.RGBA{}
@@ -93,6 +106,9 @@
 	return c
 }
 
+// Interpolate interpolates the color linearly between the
+// given values of the color values.
+// If the value is out of bounds false is returned.
 func (cc ColorValues) Interpolate(v float64) (color.RGBA, bool) {
 	if len(cc) == 0 || v < cc[0].Value || v > cc[len(cc)-1].Value {
 		return color.RGBA{}, false
@@ -148,6 +164,12 @@
 	return color.RGBA{}, false
 }
 
+// ParseColorValues parses a string to a list of color values.
+// The value/color pairs are separated by ','.
+// A color/value pair is separated with ':'.
+// f ':' is missing it is assumed that only the value is given.
+// The missing color is interpolated from fore and aftermost
+// value/colors pairs.
 func ParseColorValues(s string) (ColorValues, error) {
 
 	var err error