radionica3d/backend/preview_utils.py

import matplotlib.pyplot as plt
from stl import mesh
from mpl_toolkits import mplot3d
import os

def generate_stl_preview(stl_path: str, output_path: str):
    """
    Generates a PNG preview image for an STL file.
    """
    try:
        # Load the STL file
        your_mesh = mesh.Mesh.from_file(stl_path)

        # Create a new plot
        figure = plt.figure(figsize=(8, 8))
        # Use transparent background for a premium look
        figure.patch.set_alpha(0.0)
        
        axes = figure.add_subplot(111, projection='3d')
        axes.set_facecolor((0,0,0,0)) # Transparent background inside plot

        # Add the mesh to the plot
        poly = mplot3d.art3d.Poly3DCollection(your_mesh.vectors)
        # Professional-looking blue/gray color
        poly.set_facecolor([0.2, 0.5, 0.8, 0.9])
        poly.set_edgecolor([0.1, 0.1, 0.1, 0.2])
        axes.add_collection3d(poly)

        # Auto-scale the plot
        scale = your_mesh.points.flatten()
        axes.auto_scale_xyz(scale, scale, scale)
        
        # Hide axes for a clean look
        axes.set_axis_off()
        
        # Adjust view for better perspective
        axes.view_init(elev=30, azim=45)

        # Save the result
        plt.savefig(output_path, dpi=100, bbox_inches='tight', transparent=True)
        plt.close(figure)
        return True
    except Exception as e:
        print(f"Error generating preview: {e}")
        return False