modify image to black text on white background

Question

I have an image that need to do OCR (Optical Character Recognition) to extract all data.

First I want to convert color image to black text on white background in order to improve OCR accuracy.

I try below code

from PIL import Image
img = Image.open("data7.png")
img.convert("1").save("result.jpg")

it gave me below unclear image

I expect to have this image

Then, I will use pytesseract to get a dataframe

import pytesseract as tess
file = Image.open("data7.png")
text = tess.image_to_data(file,lang="eng",output_type='data.frame')
text

Finally,the dataframe I want to get like below

Answer 1

Here's a vanilla Pillow solution. Just grayscaling the image gives us okay results, but the green text is too faint.

So, we first scale the green channel up (sure, it might clip, but that's not a problem here), then grayscale, invert and auto-contrast the image.

from PIL import Image, ImageOps

img = Image.open('rqDRe.png').convert('RGB')

r, g, b = img.split()

img = Image.merge('RGB', (
    r,
    g.point(lambda i: i * 3),  # brighten green channel
    b,
))

img = ImageOps.autocontrast(ImageOps.invert(ImageOps.grayscale(img)), 5)

img.save('rqDRe_processed.png')

output