Python：将RAW图像转换为PNG

The raw image you have posted is 12 bit per pixel but without packing.
The 12 bits data are stored in the higher 12 bits of every 16 bits.

We can see by the size of the file, that there are 2 bytes per pixel:
7962624 = 2048*1944*2

我们可以用uint16个元素表示12位数据，如下所示:

 ------------------------------------------------------------------------------- 
|    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |
| b11| b10| b9 | b8 | b7 | b6 | b5 | b4 | b3 | b2 | b1 | b0 |  0 |  0 |  0 |  0 |
 -------------------------------------------------------------------------------

This format is much more simple to work with compared to the 12 bits packed format...
We don't need to unpack the data, we may look at it as 16 bits per pixel.

代码示例:

import cv2
import numpy as np

width = 2048
height = 1944

with open("raw_image.ims_rgb", "rb") as rawimg:
    # Read the raw image as uint16 (two bytes per pixel).
    bayer_im = np.fromfile(rawimg, np.uint16, width * height).reshape(height, width)

    # The 12 bits of each pixel are stored in the upper 12 bits of every uint16 element.
    # The lower 4 bits of the uint16 element are zeros.
    # <--- 16 bits -->
    # ************0000
    # <-12 bits -><4->    
    #    data     zeros

    # Apply Demosacing.
    # It look like COLOR_BAYER_BG2BGR gives the best result, but it hard to tell from the given input.
    bgr = cv2.cvtColor(bayer_im, cv2.COLOR_BAYER_BG2BGR)  # The result is BGR format with 16 bits per pixel range [0, 2^16-1].

    # Apply manual "white balance".
    # The result image is greenish - this is normal for most cameras.
    # We may fix it by scaling up the red and the blue color channels.
    # It look like approximate scaling is about 1.5 for the red and about 1.25 for the blue.
    bgr[:, :, 0] = (bgr[:, :, 0].astype(np.float32)*1.25).clip(0, 65535).astype(np.uint16)
    bgr[:, :, 2] = (bgr[:, :, 2].astype(np.float32)*1.5).clip(0, 65535).astype(np.uint16)


    # Show image for testing (multiply by 16 because imshow requires full uint16 range [0, 2^16-1]).
    cv2.imshow('bgr', cv2.resize(bgr, [width//10, height//10]))
    cv2.waitKey()
    cv2.destroyAllWindows()

    # Save the output as tiff with 16 bits per color component.
    cv2.imwrite("rgb16.tif", bgr)

We can see, it's a picture of the moon:

月亮不是最好的 Select ，因为我们无法验证 colored颜色 的正确性...

Note:
I "manually" scaled up the red and the blue color channels to make the moon gray (instead of green).
We may refer the scaling as manual White Balance.