[FIXED] PIL image shows OK but saves black

Issue

Using PIL Image to binarize an image to optimize OCR shows good results on-screen but saves all black PNG. And when passing the image object to process with pytesseract it also returns no text...
Note: I don't really need to save the processed image as long as the OCR works.

basepath = 'img_bin/'
image_list = os.listdir(basepath)

for file in image_list:
    if os.path.isfile(os.path.join(basepath, file)):
        print(file)

        img = Image.open(basepath+file).convert("L")
        
        img = ImageOps.invert(img)
       
        threshold = 20
        table = []
        pixelArray = img.load()
        for y in range(img.size[1]):  # binaryzate it
            List = []
            for x in range(img.size[0]):
                if pixelArray[x,y] > threshold:
                    List.append(0)
                else:
                    List.append(255)
            table.append(List)

        img = Image.fromarray(np.array(table))

        img.show()

        img.save(basepath+'processed.png')
        img_lines = pytesseract.image_to_string(img)

        print(len(img_lines))
        print(img_lines)

OUTPUTS:

print(len(img_lines)) -> 1
print(img_lines)   -> <0x0c>

img.show():

saved 'processed.png'

Solution

You need to convert the image mode to RGB:

if img.mode != 'RGB':
    img = img.convert('RGB')
img.save(basepath+'processed.png')

That's because the save method assumes RGB mode.

Answered By - Amin Gheibi