這是我在佈署LINEBOT遇到的問題，當我想要使用到影像文字辨識時，Tesseract-OCR這個模組可以幫助我們完成一些簡單低階的文字辨識，但要把Tesseract-OCR的buildpack放到heroku上面，這讓我花了不少時間，以下是我實作過程，同時也在我的github中有範例程式碼給大家參考指教。

我的github:

https://github.com/kevin1061517/python-deploy-Tesseract-OCR-to-Heroku 

Descript

Because I have stuck on the this question for two days,I take some notes to remind me of deeploying the Tesseract-OCR to Heroku.First, Tesseract is an OCR sponsored by Google. It is open-source and its binaries are available for lots of platforms, Additionally, it is a popular go-to library when OCR functionalities are required in an app. Setting up Tesseract-OCR is a procedure in popular development environments such as Heroku.Most of all,the following article is the process of deploying and coding.

Python Code

import pytesseract
from PIL import Image
pytesseract.pytesseract.tesseract_cmd = '/app/.apt/usr/bin/tesseract'
image = Image.open(path)
t = pytesseract.image_to_string(image)
line_bot_api.reply_message(event.reply_token,TextSendMessage(text=t))

Focus on the path!!! -> '/app/.apt/usr/bin/tesseract'

step

1.Add heroku-apt-buildpack into buildpacks on heroku:

You can use the command following:

heroku buildpacks:add --index 1 https://github.com/heroku/heroku-buildpack-apt

or you can input the https://github.com/heroku/heroku-buildpack-apt by using Graphical interface on heroku 

2.Create a file named as Aptfile in your app directory and paste the following:

tesseract-ocr
tesseract-ocr-eng

You must create the file named as Aptfile,or the error will emerge. 

3.set a heroku config variable named TESSDATA_PREFIX. This is the path to the data downloaded by the tesseract-ocr-eng package.

You can use the command following:

heroku config:set TESSDATA_PREFIX=/app/.apt/usr/share/tesseract-ocr/tessdata

or you can input the TESSDATA_PREFIX=/app/.apt/usr/share/tesseract-ocr/tessdata by using Graphical interface on heroku 

Notes

1.I got errors when I paste the tesseract-ocr into the requirements.txt.Because

• I used to add buildpack on heroku,I always need to input my required module into requirements.txt.But in this case,you never need the requirements.txt.

2.You must set a heroku config variable named TESSDATA_PREFIX,and inputing the TESSDATA_PREFIX's path.

• the error image of ignoring the configuration of variable named TESSDATA_PREFIX

3.Most of all,how can I find the main file named tesseract on heroku.

• First I would execuate the cmd command on heroku CLI and perform certain commands in the following commands.I should step into bash in order to find the path of tesseract on heroku bash.

heroku run bash
which tesseract
.......

• Focus on fourth line

LINEBOT screenshop

Code

..
..
..
def template_img(path):
            print('temp---------'+str(path))
            buttons_template = TemplateSendMessage(
            alt_text='news template',
            template=ButtonsTemplate(
                title='你傳來的是照片喔',
                text='請選擇怎樣處理',
                thumbnail_image_url='https://i.imgur.com/GoAYFqv.jpg',
                actions=[
                    PostbackTemplateAction(
                        label='影像文字翻譯辨識',
                        text='請稍等....',
                        data = 'trans/{}'.format(path)
                    ),
                    PostbackTemplateAction(
                        label='影像儲存至相簿',
                        text='請稍等....',
                        data = 'image/{}'.format(path)
                    )
                ]
            )
            )
            return buttons_template
@handler.add(PostbackEvent)
def handle_postback(event):
    temp = event.postback.data
    s = ''
    if temp[:5] == 'image':
     print('------postback'+str(temp))
     t = temp.split('/')
     path = '/{}/{}'.format(t[2],t[3])
     print('postback---------'+str(path))
     img_id = 1
     t = fb.get('/pic',None)
     if t!=None:
         count = 1
         for key,value in t.items():
            if count == len(t):#取得最後一個dict項目
                img_id = int(value['id'])+1
            count+=1
     try:

        client = ImgurClient(client_id, client_secret, access_token, refresh_token)
        config = {
            'album': album_id,
            'name' : img_id,
            'title': img_id,
            'description': 'Cute kitten being cute on'
        }
        client.upload_from_path(path, config=config, anon=False)
        os.remove(path)
        line_bot_api.reply_message(event.reply_token,[TextSendMessage(text='上傳成功'),image_reply])
     except  Exception as e:
        t = '上傳失敗'+str(e.args)
        line_bot_api.reply_message(event.reply_token,TextSendMessage(text=t))
    elif temp[:5] == 'trans':
     t = temp.split('/')
     path = '/{}/{}'.format(t[2],t[3])
     print('postback----'+str(path)) 
     pytesseract.pytesseract.tesseract_cmd = '/app/.apt/usr/bin/tesseract'
     image = Image.open(path)
     t = pytesseract.image_to_string(image)
     line_bot_api.reply_message(event.reply_token,TextSendMessage(text=t))

#process image
@handler.add(MessageEvent,message=ImageMessage)
def handle_msg_img(event):
    message_content = line_bot_api.get_message_content(event.message.id)
    with tempfile.NamedTemporaryFile(prefix='jpg-', delete=False) as tf:
        for chunk in message_content.iter_content():
            tf.write(chunk)
        tempfile_path = tf.name
    path = tempfile_path

    buttons_template = template_img(path)
    line_bot_api.reply_message(event.reply_token,buttons_template)
..
..
..

Reference

https://stackoverflow.com/questions/42370732/heroku-error-opening-data-file-app-vendor-tesseract-ocr-tessdata-eng-traineddat 
https://github.com/heroku/heroku-buildpack-apt 
https://medium.com/@pro_science108/configurin-tesseract-ocr-in-heroku-16-444a4c079c41