examples, some fixes

examples/annotations/main.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+
+	/*
+	   In this example we add an `Annotation` series, which is a special type of series that
+	   draws annotation labels at given X and Y values (as translated by their respective ranges).
+
+	   It is important to not that the chart automatically sizes the canvas box to fit the annotations,
+	   As well as automatically assign a series color for the `Stroke` or border component of the series.
+
+	   The annotation series is most often used by the original author to show the last value of another series, but
+	   they can be used in other capacities as well.
+	*/
+
+	graph := chart.Chart{
+		Series: []chart.Series{
+			chart.ContinuousSeries{
+				XValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
+				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
+			},
+			chart.AnnotationSeries{
+				Annotations: []chart.Annotation{
+					{X: 1.0, Y: 1.0, Label: "One"},
+					{X: 2.0, Y: 2.0, Label: "Two"},
+					{X: 3.0, Y: 3.0, Label: "Three"},
+					{X: 4.0, Y: 4.0, Label: "Four"},
+					{X: 5.0, Y: 5.0, Label: "Five"},
+				},
+			},
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	graph.Render(chart.PNG, res)
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	http.ListenAndServe(":8080", nil)
+}