ppm.py

#!/usr/bin/env python3
"""
ppm_thick_flipped_tile2x.py   
"""

import numpy as np

def main():
    txtfile = "grid.txt"
    print(f"Reading {txtfile}...")

    data = np.loadtxt(txtfile, skiprows=1, usecols=(0,1,2,3))
    x = data[:,0].astype(int)
    y = data[:,1].astype(int)
    lcells = data[:,2]
    lcomp = data[:,3]

    nx = int(x.max()) + 1
    ny = int(y.max()) + 1

    grid = np.full((ny, nx), np.nan, dtype=float)
    grid[y-1, x-1] = np.where(lcells > 0.01, lcomp, np.nan)

    # R=1 solid thickening
    solid = np.isnan(grid)
    thickened = solid.copy()
    for dy in [-1,0,1]:
        for dx in [-1,0,1]:
            if dy == 0 and dx == 0: continue
            thickened |= np.roll(np.roll(solid, dy, axis=0), dx, axis=1)
    grid[thickened] = np.nan

    grid = np.flipud(grid)                    # grow upward
    grid_tiled = np.hstack((grid, grid))      # 2× periodic

    # === COLOR SCALE MATCHING ===
    def to_ppm_color(val):
        if np.isnan(val):
            return (0, 0, 0)                    # solid black

        # Normalize roughly 0–20 wt% (adjust as needed)
        t = max(0.0, min(1.0, val / 20.0))

        if t < 0.2:
            r = 255
            g = int(255 * (t / 0.2))
            b = 0
        elif t < 0.4:
            r = int(255 * (1.0 - (t-0.2)/0.2))
            g = 255
            b = 0
        elif t < 0.6:
            r = 0
            g = 255
            b = int(255 * ((t-0.4)/0.2))
        elif t < 0.8:
            r = 0
            g = int(255 * (1.0 - (t-0.6)/0.2))
            b = 255
        else:
            r = int(100 * ((t-0.8)/0.2))
            g = 0
            b = 255

        return (r, g, b)

    # Write PPM
    with open("out.ppm", "wb") as f:
        f.write(b"P6\n")
        f.write(f"{2*nx} {ny}\n".encode())
        f.write(b"255\n")
        for j in range(ny):
            for i in range(2*nx):
                r,g,b = to_ppm_color(grid_tiled[j,i])
                f.write(bytes([r, g, b]))

    print("✅ out.ppm created!")
    print(f"   Size: {2*nx} × {ny}")

if __name__ == "__main__":
    main()