JPEG to PDF N-up with pypdfium2

tile.py

# SPDX-FileCopyrightText: 2023 mara004
# SPDX-License-Identifier: CC-BY-4.0 OR Apache-2.0 OR BSD-3-Clause

import math
import argparse
import itertools
import pypdfium2 as pdfium 
from pathlib import Path

parser = argparse.ArgumentParser()
parser.add_argument("files", nargs="+", type=Path)
parser.add_argument("--output", "-o", type=Path)
args = parser.parse_args()

ROWS, COLS = 2, 2
PAGE_W, PAGE_H = 595, 842
ROTATION = 90
H_ALIGNS = ["right", "left"]  # left, mid, right
V_ALIGNS = ["mid"] * ROWS  # bottom, mid, top


def main():
    
    n_tiles = ROWS*COLS
    box_w, box_h = PAGE_W/COLS, PAGE_H/ROWS
    n_pages = math.ceil( len(args.files) / n_tiles )
    
    new_pdf = pdfium.PdfDocument.new()
    
    for i in range(n_pages):
        page = new_pdf.new_page(PAGE_W, PAGE_H)
        
        for r, c in itertools.product(range(ROWS), range(COLS)):
            
            file_idx = i*n_tiles + r*COLS + c
            if not file_idx < len(args.files):
                break
            
            img = pdfium.PdfImage.new(new_pdf)
            img.load_jpeg(args.files[file_idx])
            page.insert_obj(img)
            px_w, px_h = img.get_size()
            
            tile_w, tile_h = box_w, box_h
            if ROTATION in (90, 270):
                tile_w, tile_h = tile_h, tile_w
            
            scale = min(tile_w/px_w, tile_h/px_h)
            scaled_w, scaled_h = px_w*scale, px_h*scale
            w_diff, h_diff = tile_w-scaled_w, tile_h-scaled_h
            tile_w, tile_h = scaled_w, scaled_h
            
            m = pdfium.PdfMatrix()
            m = m.scale(tile_w, tile_h)
            
            if ROTATION != 0:
                # TODO pypdfium2: consider adding abstraction for rotating an object around a point on itself - translating back and forth is slightly annoying
                m = m.translate(-tile_w/2, -tile_h/2)
                m = m.rotate(ROTATION)
                if ROTATION in (90, 270):
                    tile_w, tile_h = tile_h, tile_w
                    w_diff, h_diff = h_diff, w_diff
                m = m.translate(tile_w/2, tile_h/2)
            
            pos_y = PAGE_H - box_h*(r+1)
            pos_x = box_w * c
            pos_x += dict(left=0, mid=w_diff/2, right=w_diff)[ H_ALIGNS[c] ]
            pos_y += dict(bottom=0, mid=h_diff/2, top=h_diff)[ V_ALIGNS[r] ]
            
            m = m.translate(pos_x, pos_y)
            img.set_matrix(m)
        
        page.gen_content()
    
    new_pdf.save(args.output)


main()