Save 1 bit deep binary image in Python

问题

I have a binary image in Python and I want to save it in my pc. I need it to be a 1 bit deep png image once stored in my computer. How can I do that? I tried with both PIL and cv2 but I'm not able to save it with 1 bit depth.

回答1:

Use:

cv2.imwrite(<image_name>, img, [cv2.IMWRITE_PNG_BILEVEL, 1])

(this will still use compression, so in practice it will most likely have less than 1 bit per pixel)

回答2:

If you're not loading pngs or anything the format does behave pretty reasonably to just write it. Then your code doesn't need PIL or any of the headaches of various imports and imports on imports etc.

import struct
import zlib
from math import ceil


def write_png_1bit(buf, width, height, stride=None):
    if stride is None:
        stride = int(ceil(width / 8))
    raw_data = b"".join(
        b'\x00' + buf[span:span + stride] for span in range(0, (height - 1) * stride, stride))

    def png_pack(png_tag, data):
        chunk_head = png_tag + data
        return struct.pack("!I", len(data)) + chunk_head + struct.pack("!I", 0xFFFFFFFF & zlib.crc32(chunk_head))

    return b"".join([
        b'\x89PNG\r\n\x1a\n',
        png_pack(b'IHDR', struct.pack("!2I5B", width, height, 1, 0, 0, 0, 0)),
        png_pack(b'IDAT', zlib.compress(raw_data, 9)),
        png_pack(b'IEND', b'')])

Adapted from: http://code.activestate.com/recipes/577443-write-a-png-image-in-native-python/ (MIT)

by reading the png spec: https://www.w3.org/TR/PNG-Chunks.html

Keep in mind the 1 bit data from buf, should be written left to right like the png spec wants in normal non-interlace mode (which we declared). And the excess data pads the final bit if it exists, and stride is the amount of bytes needed to encode a scanline. Also, if you want those 1 bit to have palette colors you'll have to write a PLTE block and switch the type to 3 rather than 0. Etc.

来源：https://stackoverflow.com/questions/50268092/save-1-bit-deep-binary-image-in-python