Python 使用Tesseract识别图片中的字符

环境：Python3， Windows

首先先得安装Pillow和pytesseract:

pip install pytesseract
pip install pillow

之后需要在操作系统里安装Tesseract：

1. 访问https://github.com/UB-Mannheim/tesseract/wiki
2. 下载tesseract-ocr-w64-setup-v4.1.0.20190314 (rc1)
3. 安装下载好的tesseract-ocr-w64-setup-v4.1.0.20190314.exe，安装过程中最好选择Chinese(simplified)语言
4. 安装完毕后，将tesseract的目录（默认“C:\Program Files\Tesseract-OCR”）加入到系统PATH变量中

使用Windows CMD确认安装结果：

C:\Users\xxx>tesseract -v
tesseract v4.0.0.20190314
 leptonica-1.78.0
  libgif 5.1.4 : libjpeg 8d (libjpeg-turbo 1.5.3) : libpng 1.6.34 : libtiff 4.0.9 : zlib 1.2.11 : libwebp 0.6.1 : libopenjp2 2.2.0
 Found AVX2
 Found AVX
 Found SSE

C:\Users\xxx>tesseract --list-langs
List of available languages (4):
chi_sim
eng
osd
script/HanS

tesseract-4.0.0a支持以下psm参数：

Page segmentation modes:
  0    Orientation and script detection (OSD) only.
  1    Automatic page segmentation with OSD.
  2    Automatic page segmentation, but no OSD, or OCR.
  3    Fully automatic page segmentation, but no OSD. (Default)
  4    Assume a single column of text of variable sizes.
  5    Assume a single uniform block of vertically aligned text.
  6    Assume a single uniform block of text.
  7    Treat the image as a single text line.
  8    Treat the image as a single word.
  9    Treat the image as a single word in a circle.
 10    Treat the image as a single character.
 11    Sparse text. Find as much text as possible in no particular order.
 12    Sparse text with OSD.
 13    Raw line. Treat the image as a single text line,
                        bypassing hacks that are Tesseract-specific.

python3 用法：

from PIL import Image
import pytesseract

img = Image.open('shot.png')
ocr_str = pytesseract.image_to_string(img, lang="eng", config="--psm 7")
print(ocr_str)

如果图片中是纯数字，可以使用：

ocr_str = pytesseract.image_to_string(image, lang='eng', \
        config='--psm 10 --oem 3 -c tessedit_char_whitelist=0123456789')