Method write_as_bmp

png.py:513–555

Donno how to compress the idat chunk properly without writing the whole function myself and dumping the zlib

(img, path="image.bmp")

    def write_as_bmp(img, path="image.bmp"):
        """
        Donno how to compress the idat chunk properly without 
        writing the whole function myself and dumping the zlib
        """
        if not path.endswith(".bmp"):
            path += ".bmp"
        if isinstance(img, Png):
            img = img.pixels

        width = len(img[0])
        height = len(img)
        size = 54 + 4 * ceil(width/4) * height * 3
        header = (b'BM' + 
                  size.to_bytes(4, "little") + 
                  (0).to_bytes(2, "little") + 
                  (0).to_bytes(2, "little") + 
                  (54).to_bytes(4, "little"))

        dib_header = (
            (40).to_bytes(4, "little") +
            width.to_bytes(4, "little") + 
            height.to_bytes(4, "little") +
            (1).to_bytes(2, "little") +
            (24).to_bytes(2, "little") +      # bit depth
            (0).to_bytes(4, "little") +       # No compression
            (0).to_bytes(4, "little") + 
            (1).to_bytes(4, "little") +
            (1).to_bytes(4, "little") +
            (0).to_bytes(4, "little") +
            (0).to_bytes(4, "little")
        )
        pixels = []
        img.reverse()
        for row in img:
            for pixel in row:
                pixels.append(pixel[2].to_bytes(1, 'little'))
                pixels.append(pixel[1].to_bytes(1, 'little'))
                pixels.append(pixel[0].to_bytes(1, 'little'))
            pixels.append(b'\x00' * (width % 4))
        pixels = b''.join(pixels)
        with open(path, "wb") as image_file:
            image_file.write(header + dib_header + b"\x00" * 6 + pixels)