Terraria Mobile Unity 2DTexture merge _A.png _P.png

draw.py

from PIL import Image
import numpy as np
import os
from multiprocessing import Pool
import multiprocessing
from functools import partial
from numpy.core.multiarray import array

"""
# _P
Pixel data

# _A
Alpha data
override if exists

# regular image
can be split into blocks

blocks indexed from up to down, right to left

210
543
876

pixel color = _P[block index][pixel alpha value]

"""

"""
change applied to img
"""


def draw(img, pimg, aimg=None):
    override_alpha = aimg is not None
    width, height = img.size

    colors = np.array(pimg)
    _, blocks = pimg.size

    # block colums
    block_cols = int(np.sqrt(blocks))
    # block width
    block_w = width // block_cols

    # block rows
    block_rows = int(np.ceil(height / block_w))

    # block-colors index
    block_i = 0
    for b_row in range(block_rows):
        for b_col in reversed(range(block_cols)):
            b_colors = colors[block_i]
            if block_i < colors.shape[0] - 1:
                block_i += 1

            # block coord (left up)
            bx = b_col * block_w
            by = b_row * block_w

            # inside block coord
            for x in range(block_w):
                px = bx + x
                if px >= width:
                    continue
                for y in range(block_w):
                    py = by + y
                    if py >= height:
                        continue

                    d = img.getpixel((px, py))[3]
                    r, g, b, a = b_colors[d]
                    if override_alpha:
                        a = aimg.getpixel((px, py))[3]
                    img.putpixel((px, py), (r, g, b, a))


def merge(pfile, save=True, show=False, clean=True, destDir=None):
    # cut _P.png
    name = os.path.basename(pfile)[:-6]
    dir = os.path.dirname(pfile)

    file = os.path.join(dir, f"{name}.png")
    afile = os.path.join(dir, f"{name}_A.png")

    aimg = None
    if os.path.exists(afile):
        aimg = Image.open(afile)

    with Image.open(pfile) as pimg:
        with Image.open(file) as img:
            draw(img, pimg, aimg)
            if save:
                if destDir is not None:
                    file = os.path.join(destDir, f"{name}.png")
                img.save(file)
            if show:
                img.show()

    if aimg is not None:
        aimg.close()

    if clean:
        os.remove(pfile)
        if os.path.exists(afile):
            os.remove(afile)


def get_files(path):
    return [os.path.join(path, f) for f in os.listdir(path) if f.endswith("_P.png")]


if __name__ == "__main__":
    os.chdir(os.path.dirname(os.path.abspath(__file__)))
    with Pool(multiprocessing.cpu_count()) as pool:
        pool.map(
            partial(merge, save=True, show=False, clean=False, destDir="test_out"),
            get_files("test"),
        )

https://docs.unity3d.com/Manual/class-SpriteAtlas.html
https://en.wikipedia.org/wiki/Texture_atlas