使用go实现百度OCR文字识别接口

百度OCR文字识别提供了每天50000次免费接口的调用，但是没有提供go语言示例。下面是使用go写的一个示例

package baidu

import (
    "compress/gzip"
    "encoding/base64"
    "encoding/json"
    "fmt"
    "io"
    "io/ioutil"
    "log"
    "net/http"
    "net/url"
    "os"
    "strings"
)

const (
    // 客户端凭证类型，固定为client_credentials
    grantType string = "client_credentials"
    // 应用的API Key
    apiKey string = ""
    // 应用的Secret Key
    secretKey string = ""
    // 授权服务地址
    tokenUrl string = "https://aip.baidubce.com/oauth/2.0/token"
    // 文字识别（高精度）API接口地址
    accurateBasicUrl string = "https://aip.baidubce.com/rest/2.0/ocr/v1/accurate_basic"
)

type accessToken struct {
    RefreshToken string `json:"refresh_token"`
    ExpiresIn uint32 `json:"expires_in"`
    Scope string `json:"scope"`
    SessionKey string `json:"session_key"`
    AccessToken string `json:"access_token"`
    SessionSecret string `json:"session_secret"`
}

type WordsResult struct {
    Words string `json:"words"`
}

type Words struct {
    WordsResult []WordsResult `json:"words_result"`
    LogId uint64 `json:"log_id"`
    WordsResultNum uint32 `json:"words_result_num"`
}

// 获取access_token
// access_token有效期一般是30天
// 官方文档：https://ai.baidu.com/ai-doc/REFERENCE/Ck3dwjhhu
func getAccessToken() (data accessToken) {
    requestUrl := fmt.Sprintf("%s?grant_type=%s&client_id=%s&client_secret=%s", tokenUrl, grantType, apiKey, secretKey)
    response, e := http.Get(requestUrl)
    defer response.Body.Close()
    printError(e)
    s := unCoding(response)
    e = json.Unmarshal([]byte(s), &data)
    printError(e)
    return
}

// 文字识别（高精度）
// 官方文档：https://cloud.baidu.com/doc/OCR/s/1k3h7y3db
// img 图片地址
func AccurateBasic(img string) (data Words) {
    requestUrl := fmt.Sprintf("%s?access_token=%s", accurateBasicUrl, getAccessToken().AccessToken)
    f, e := os.Open(img)
    printError(e)
    defer f.Close()
    d, e := ioutil.ReadAll(f)
    printError(e)
    const base64Table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    var coder = base64.NewEncoding(base64Table)
    imgString := coder.EncodeToString(d)
    printError(e)
    values := url.Values{"image": {imgString}}
    response ,e := http.Post(requestUrl, "application/x-www-form-urlencoded", strings.NewReader(values.Encode()))
    defer response.Body.Close()
    s := unCoding(response)
    e = json.Unmarshal([]byte(s), &data)
    printError(e)
    return
}

func unCoding(r *http.Response) (body string) {
    if r.StatusCode == 200 {
        switch r.Header.Get("Content-Encoding") {
        case "gzip":
            reader, _ := gzip.NewReader(r.Body)
            for {
                buf := make([]byte, 1024)
                n, err := reader.Read(buf)
                if err != nil && err != io.EOF {
                    panic(err)
                }
                if n == 0 {
                    break
                }
                body += string(buf)
            }
        default:
            bodyByte, _ := ioutil.ReadAll(r.Body)
            body = string(bodyByte)
        }
    } else {
        bodyByte, _ := ioutil.ReadAll(r.Body)
        body = string(bodyByte)
    }
    return
}

func printError(e error) {
    if e != nil {
        log.Println(e)
        os.Exit(1)
    }
}

测试一下

func main() {
    fmt.Println(baidu.AccurateBasic("./test.jpg"))
}

图片如下

image.png

识别如下

image.png