python - 使用 PYTHON PIL 从验证码图像中去除背景噪声线

Question

我有一个经过处理的验证码图像(放大)看起来像:

如您所见，“TEXT”的字体大小比噪声线的宽度稍大。
因此，我需要一种算法或代码来从该图像中去除噪声线。

在 Python PIL 库和下面提到的斩波算法的帮助下，我没有得到 OCR 可以轻松读取的输出图像。

这是我尝试过的 Python 代码:

import PIL.Image
import sys

# python chop.py [chop-factor] [in-file] [out-file]

chop = int(sys.argv[1])
image = PIL.Image.open(sys.argv[2]).convert('1')
width, height = image.size
data = image.load()

# Iterate through the rows.
for y in range(height):
    for x in range(width):

        # Make sure we're on a dark pixel.
        if data[x, y] > 128:
            continue

        # Keep a total of non-white contiguous pixels.
        total = 0

        # Check a sequence ranging from x to image.width.
        for c in range(x, width):

            # If the pixel is dark, add it to the total.
            if data[c, y] < 128:
                total += 1

            # If the pixel is light, stop the sequence.
            else:
                break

        # If the total is less than the chop, replace everything with white.
        if total <= chop:
            for c in range(total):
                data[x + c, y] = 255

        # Skip this sequence we just altered.
        x += total


# Iterate through the columns.
for x in range(width):
    for y in range(height):

        # Make sure we're on a dark pixel.
        if data[x, y] > 128:
            continue

        # Keep a total of non-white contiguous pixels.
        total = 0

        # Check a sequence ranging from y to image.height.
        for c in range(y, height):
            # If the pixel is dark, add it to the total.
            if data[x, c] < 128:
                total += 1

            # If the pixel is light, stop the sequence.
            else:
                break

        # If the total is less than the chop, replace everything with white.
        if total <= chop:
            for c in range(total):
                data[x, y + c] = 255

        # Skip this sequence we just altered.
        y += total

image.save(sys.argv[3])

所以，基本上我想知道一种更好的算法/代码来消除噪声，从而能够使 OCR(Tesseract 或 pytesser)可读图像。

Answer 1

要快速去除大部分线条，您可以将具有两个或更少相邻黑色像素的所有黑色像素变为白色。那应该修复杂散线。然后，当您有很多“ block ”时，您可以移除较小的 block 。

这是假设示例图像已被放大，并且线条只有一个像素宽。