lenticufy.py

import png
from PIL import Image, ImageMath

import array
import math


def _planes_from_png(filename):
    with open(filename, "rb") as png_file:
        reader = png.Reader(filename)
        width, height, image_array, meta = reader.read_flat()
        image_array_32 = array.array("I", image_array)
        for plane_index in range(meta["planes"]):
            yield Image.frombytes("I", (width, height), image_array_32[plane_index::3].tobytes())


def _rescaled_plane(image, new_width, aspect_angle_deg):
    x_margin = abs(0.5 * image.width * (1-math.sin(math.radians(90 - aspect_angle_deg))))
    return image.resize(
        size=(new_width, image.height,),
        resample=Image.LANCZOS,
        box=(x_margin, 0, image.width - x_margin, image.height),
    )


def _get_pixel_column_mapping(n_strips, n_pixel_columns, n_frames):
    return ((column, math.floor(frac_frame*n_frames), int(strip)) for column, (frac_frame, strip) in (
        (column, math.modf(float(column)*n_strips/n_pixel_columns),)
        for column in range(n_pixel_columns)
    ))


def _peek(x):
    import pdb; pdb.set_trace()
    return x


def lenticufy(filenames, combined_image_width=2550, startangle_deg=45, n_strips=108, exposure_factor=2.6):
    combined_image = None
    conversion_expression = "convert(float(x)*{}, 'L')".format(exposure_factor/256.0)

    pixel_column_mapping = tuple(_get_pixel_column_mapping(n_strips, combined_image_width, len(filenames)))

    for file_index, filename in enumerate(filenames):
        print(f"Processing {filename!r}")
        rescaled_image = Image.merge("RGB", tuple(
            ImageMath.eval(
                conversion_expression,
                x=_rescaled_plane(plane, n_strips, startangle_deg * (1 - (2.0 * file_index)/len(filenames))),
            ) for plane in _planes_from_png(filename)
        ))
        combined_image = combined_image or Image.new("RGB", (combined_image_width, rescaled_image.height))

        for final_pixel_column, frame, source_pixel_column in pixel_column_mapping:
            if frame == file_index:
                combined_image.paste(
                    rescaled_image.crop(
                        (source_pixel_column, 0, source_pixel_column+1, rescaled_image.height)
                    ),
                    box=(final_pixel_column, 0),
                )

    return combined_image