How would I read a raw RGBA4444 image using Pillow?

Question

I'm trying to read a '.waltex' image, which is a 'walaber image'. It's basically just in raw image format. The problem is, it uses 'RGBA8888', 'RGBA4444', 'RGB565' and 'RGB5551' (all of which can be determined from the header), and I could not find a way to use these color specs in PIL.

I've tried doing this

from PIL import Image

with open('Carl.waltex', 'rb') as file:
    rawdata = file.read()

image = Image.frombytes('RGBA', (1024,1024), rawdata, 'raw', 'RGBA;4B')
image.show()

I've tried all the 16-bit raw modes in the last input, and I couldn't find a single one that worked. To be clear, this file is specifically 'RGBA4444' with little endian, 8 bytes per pixel.

If you need the file, then I can link it.

Answer 1

Now that I have a better idea of how your Waltex files work, I attempted to write a custom PIL Plugin for them - a new experience for me. I've put it as a different answer because the approach is very different.

You use it very simply like this:

from PIL import Image
import WaltexImagePlugin

im = Image.open('objects.waltex')
im.show()

---

You need to save the following as WaltexImagePlugin.py in the directory beside your main Python program:

from PIL import Image, ImageFile
import struct

def _accept(prefix):
    return prefix[:4] == b"WALT"

class WaltexImageFile(ImageFile.ImageFile):

    format = "Waltex"
    format_description = "Waltex texture image"

    def _open(self):
        header = self.fp.read(HEADER_LENGTH)
        magic, vers, fmt, w, h, _ = struct.unpack('4sBBHH6s', header)

        # size in pixels (width, height)
        self._size = w, h

        # mode setting
        self.mode = 'RGBA'

        # Decoder
        if fmt == 0:
            # RGBA8888
            # Just use built-in raw decoder
            self.tile = [("raw", (0, 0) + self.size, HEADER_LENGTH, (self.mode, 
0, 1))]
        elif fmt == 3:
            # RGBA4444
            # Use raw decoder with custom RGBA;4B unpacker
            self.tile = [("raw", (0, 0) + self.size, HEADER_LENGTH, ('RGBA;4B', 
0, 1))]


Image.register_open(WaltexImageFile.format, WaltexImageFile, _accept)

Image.register_extensions(
    WaltexImageFile.format,
    [
        ".waltex"
    ],
)

HEADER_LENGTH = 16

---

It works perfectly for your RGBA888 images, but cannot quite handle the byte ordering of your RGBA444 file, so you need to reverse it for those images. I used this:

...
...
im = Image.open(...)

# Split channels and recombine in correct order
a, b, c, d = im.split()
im = Image.merge((c,d,a,b))

If anyone knows how to use something in the Unpack.c file to do this correctly, please ping me. Thank you.