原文：https://blog.csdn.net/zangdaiyang1991/article/details/105200062
----------------------------------------------------------------
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
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
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
asd-asd", 20}, {"asdascascasdasdasd.go
asdasd-asdasd", 30}, {"asasdasd.asdasd]
asdasd-asda", 100},
{"asdasdasda.go
asdasd-asdasd", 20}, {"asdasd.asdasd
geass", 30}, {"asdasdasd
asdasd-asdasd", 100},
{"asdasd_adsdasd_dasdasd-asd", 20}, {"asdascasdcad
asdasdasda", 30}, {"asdasdasdasd", 100},
{"asdasclkhy9p867p9", 20}}},
}
for _, test := range tests {
img, err := createBarChart(test.title, test.pieValues)
testAssert.Equal(img, "")
testAssert.Equal(err, nil)
}
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
相关：
https://github.com/wcharczuk/go-chart/issues/62
go-chart使用中文
go-echarts: html格式图表
————————————————
版权声明：本文为CSDN博主「藏呆羊」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/zangdaiyang1991/java/article/details/105200062