需求
邮件中实现统计信息的发送。统计信息以折线图、饼图、柱状图的形式展示。因为邮件中无法支持js解析，所以采用go-chart生成PNG图片后base64编码后发送。
<img src="data:image/png;base64,xxx">
1
go-chart实战
go-chart是个强大的go生成图片的库，但是采用默认配置生成线条较多或者文本过长的图片时，无法完美适应。默认不支持中文。但是里面的属性大多可自己定义，整体来说非常强大。
代码
package charter
import (
"bytes"
"encoding/base64"
"fmt"
"math/rand"
"os"
"time"
"github.com/wcharczuk/go-chart"
"github.com/wcharczuk/go-chart/drawing"
)
const (
lineChartXAxisName = "Date"
lineChartYAxisName = "Count"
lineChartHeight = 700
lineChartWidth = 1280
colorMultiplier = 256
imgStrPrefix = "data:image/png;base64,"
pieLabelFormat = "%v %v"
barChartTryAgainErr = "invalid data range; cannot be zero"
)
var (
lineChartStyle = chart.Style{
Padding: chart.Box{
Top: 30,
Left: 150,
},
}
defaultChartStyle = chart.Style{
Padding: chart.Box{
Top: 30,
},
}
timeFormat = chart.TimeDateValueFormatter
)
type LineYValue struct {
Name string
Values []float64
}
type ChartValue struct {
Name string
Value float64
}
// createLineChart 创建线性图
func createLineChart(title string, endTime time.Time, values []LineYValue) (img string, err error) {
if len(values) == 0 {
return
}
// 1、计算X轴
lenX := len(values[0].Values)
// X轴内容xValues 及 X轴坐标ticks
var xValues []time.Time
var ticks []chart.Tick
for i := lenX - 1; i >= 0; i-- {
curTime := endTime.AddDate(0, 0, -i)
xValues = append(xValues, curTime)
ticks = append(ticks, chart.Tick{Value: getNsec(curTime), Label: timeFormat(curTime)})
}
// 2、生成Series
var series []chart.Series
for _, yValue := range values {
series = append(series, chart.TimeSeries{
Name: yValue.Name,
Style: chart.Style{
// 随机渲染线条颜色
StrokeColor: drawing.Color{
R: uint8(rand.Intn(colorMultiplier)),
G: uint8(rand.Intn(colorMultiplier)),
B: uint8(rand.Intn(colorMultiplier)),
A: uint8(colorMultiplier - 1), // 透明度
},
},
XValues: xValues,
YValues: yValue.Values,
})
}
// 3、新建图形
graph := chart.Chart{
Title: title,
Background: lineChartStyle,
Width: lineChartWidth,
Height: lineChartHeight,
XAxis: chart.XAxis{
Name: lineChartXAxisName,
ValueFormatter: timeFormat,
Ticks: ticks,
},
YAxis: chart.YAxis{
Name: lineChartYAxisName,
},
Series: series,
}
graph.Elements = []chart.Renderable{
chart.LegendLeft(&graph),
}
// 4、输出目标
img, err = writeLineChart(&graph)
return
}
// getNsec 获取纳秒数
func getNsec(cur time.Time) float64 {
return float64(cur.Unix() * int64(time.Second))
}
func writeLineChartToPng(c *chart.Chart) (img string, err error) {
f, _ := os.Create("graph.png")
err = c.Render(chart.PNG, f)
return
}
func writeLineChart(c *chart.Chart) (img string, err error) {
var imgContent bytes.Buffer
err = c.Render(chart.PNG, &imgContent)
if err != nil {
return
}
img = imgToStr(imgContent)
return
}
func imgToStr(imgContent bytes.Buffer) string {
return imgStrPrefix + base64.StdEncoding.EncodeToString(imgContent.Bytes())
}
// createPieChart 创建饼图
func createPieChart(title string, pieValues []ChartValue) (img string, err error) {
if len(pieValues) == 0 {
return
}
// 1、构建value
var values []chart.Value
for _, v := range pieValues {
values = append(values, chart.Value{
Value: v.Value,
Label: fmt.Sprintf(pieLabelFormat, getSimpleSensType(v.Name), formatValue(v.Value)),
})
}
// 2、新建饼图
pie := chart.PieChart{
Title: title,
Background: defaultChartStyle,
Values: values,
}
// 4、输出目标
img, err = writePieChart(&pie)
return
}
func formatValue(f float64) string {
return fmt.Sprintf("%.2fW", f/10000)
}
func writePieChartToPng(c *chart.PieChart) (img string, err error) {
f, _ := os.Create("pie.png")
err = c.Render(chart.PNG, f)
return
}
func writePieChart(c *chart.PieChart) (img string, err error) {
var imgContent bytes.Buffer
err = c.Render(chart.PNG, &imgContent)
if err != nil {
return
}
img = imgToStr(imgContent)
return
}
// createBarChart 创建柱状图
func createBarChart(title string, barValues []ChartValue) (img string, err error) {
if len(barValues) == 0 {
return
}
// 1、构建value
var values []chart.Value
for _, v := range barValues {
values = append(values, chart.Value{
Value: v.Value,
Label: v.Name,
})
}
// 2、新建饼图
bar := chart.BarChart{
XAxis: chart.Style{
TextWrap: 0, // default 1为可以溢出规定的范围
},
Width: 2560,
BarWidth: 50,
BarSpacing: 300,
Title: title,
Background: defaultChartStyle,
Bars: values,
}
// 4、输出目标
img, err = writeBarChart(&bar)
if err != nil && err.Error() == barChartTryAgainErr {
// 添加一个隐藏条目，设置透明度A为0, 设置任意属性如R不为0即可
values = append(values, chart.Value{
Style: chart.Style{
StrokeColor: drawing.Color{R: 1},
},
Value: 0,
Label: "",
})
bar.Bars = values
img, err = writeBarChart(&bar)
}
return
}
func writeBarChartToPng(c *chart.BarChart) (img string, err error) {
f, _ := os.Create("bar.png")
err = c.Render(chart.PNG, f)
return
}
func writeBarChart(c *chart.BarChart) (img string, err error) {
var imgContent bytes.Buffer
err = c.Render(chart.PNG, &imgContent)
if err != nil {
return
}
img = imgToStr(imgContent)
return
测试代码和生成图片效果
修改以上writeXxxChart为writeXxxChartToPng后，运行以下测试代码
package charter
import (
"testing"
"time"
"github.com/stretchr/testify/assert"
)
func TestCreateLineChart(t *testing.T) {
testAssert := assert.New(t)
tests := []struct {
title string
endTime time.Time
barValues []LineYValue
}{
{"line chart", time.Now(), []LineYValue{
{"asd", []float64{1, 2, 300, 100, 200, 6, 700}},
{"hgj", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"dfg45r", []float64{1, 2, 700, 100, 200, 6, 700}},
{"2342sr", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"das21-asd", []float64{300000, 200000, 400000, 100000, 400000, 450000, 400000}},
{"csc", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"mhj", []float64{1, 2, 300, 100, 200, 6, 700}},
{"876ijgh", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"fbfdv", []float64{1, 2, 300, 100, 200, 6, 700}},
{"67ds", []float64{400, 10000, 200, 50, 5, 800, 7}},
{"67bdfv", []float64{1, 2, 300, 100, 200, 6, 700}},
{"sdf324", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"vdf67", []float64{1, 2, 300, 100, 200, 6, 700}},
{"vdfs234", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"123sdf", []float64{1, 2, 700, 100, 200, 6, 700}},
{"aasdasd", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"aasd", []float64{1, 2, 300, 100, 200, 6, 700}},
{"basd", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"cczx", []float64{1, 2, 300, 100, 200, 6, 700}},
{"qweqw", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"asdadf", []float64{1, 2, 300, 100, 200, 6, 700}},
{"fghfh", []float64{400, 500000, 200, 50, 5, 800, 7}},
{"erttyrt", []float64{1, 2, 300, 100, 200, 6, 700}}}},
}
for _, test := range tests {
img, err := createLineChart(test.title, test.endTime, test.barValues)
testAssert.Equal(img, "")
testAssert.Equal(err, nil)
}
}
func TestCreatePieChart(t *testing.T) {
testAssert := assert.New(t)
tests := []struct {
title string
pieValues []ChartValue
}{
{"pie chart", []ChartValue{{"asdas", 20000}, {"q12asd", 300000}, {"ascasd", 3000}}},
}
for _, test := range tests {
img, err := createPieChart(test.title, test.pieValues)
testAssert.Equal(img, "")
testAssert.Equal(err, nil)
}
}
func TestCreateBarChart(t *testing.T) {
testAssert := assert.New(t)
tests := []struct {
title string
pieValues []ChartValue
}{
{"bar chart", []ChartValue{{"asdascasd\nasd-asd", 20}, {"asdascascasdasdasd.go\nasdasd-asdasd", 30}, {"asasdasd.asdasd]\nasdasd-asda", 100},
{"asdasdasda.go\nasdasd-asdasd", 20}, {"asdasd.asdasd\ngeass", 30}, {"asdasdasd\nasdasd-asdasd", 100},
{"asdasd_adsdasd_dasd\asd-asd", 20}, {"asdascasdcad\nasdasdasda", 30}, {"asdasdasdasd", 100},
{"asdasclkhy9p867p9", 20}}},
}
for _, test := range tests {
img, err := createBarChart(test.title, test.pieValues)
testAssert.Equal(img, "")
testAssert.Equal(err, nil)
}
}
