app.py

import os
import gradio as gr
from collections import OrderedDict
from PIL import Image, ImageDraw, ImageFont
from io import BytesIO
import time
import tempfile
import PyPDF2
import pdf2image
from datasets import load_dataset

MAX_PAGES = 50
MAX_PDF_SIZE = 100000000  # almost 100MB
MIN_WIDTH, MIN_HEIGHT = 150, 150


def equal_image_grid(images):
    def compute_grid(n, max_cols=6):
        equalDivisor = int(n**0.5)
        cols = min(equalDivisor, max_cols)
        rows = equalDivisor
        if rows * cols >= n:
            return rows, cols
        cols += 1
        if rows * cols >= n:
            return rows, cols
        while rows * cols < n:
            rows += 1
        return rows, cols

    # assert len(images) == rows*cols
    rows, cols = compute_grid(len(images))

    # rescaling to min width [height padding]
    images = [im for im in images if (im.height > 0) and (im.width > 0)]  # could be NA

    min_width = min(im.width for im in images)
    images = [im.resize((min_width, int(im.height * min_width / im.width)), resample=Image.BICUBIC) for im in images]

    w, h = max([img.size[0] for img in images]), max([img.size[1] for img in images])

    grid = Image.new("RGB", size=(cols * w, rows * h))
    grid_w, grid_h = grid.size

    for i, img in enumerate(images):
        grid.paste(img, box=(i % cols * w, i // cols * h))
    return grid


def add_pagenumbers(im_list, height_scale=40):
    def add_pagenumber(image, i):
        width, height = image.size
        draw = ImageDraw.Draw(image)
        fontsize = int((width * height) ** (0.5) / height_scale)
        font = ImageFont.truetype("Arial.ttf", fontsize)
        margin = int(2 * fontsize)
        draw.text(
            (width - margin, height - margin),
            str(i + 1),
            fill="#D00917",
            font=font,
            spacing=4,
            align="right",
        )

    for i, image in enumerate(im_list):
        add_pagenumber(image, i)


def pdf_to_grid(pdf_path):
    reader = PyPDF2.PdfReader(pdf_path)
    reached_page_limit = False
    images = []
    try:
        for p, page in enumerate(reader.pages):
            if reached_page_limit:
                break
            for image in page.images:
                im = Image.open(BytesIO(image.data))
                if im.width < MIN_WIDTH and im.height < MIN_HEIGHT:
                    continue
                images.append(im)
    except Exception as e:
        print(f"{pdf_path} PyPDF get_images {e}")
        images = pdf2image.convert_from_bytes(pdf_path)

    # simpler but slower
    # images = pdf2image.convert_from_path(pdf_path)

    if len(images) == 0:
        return None
    add_pagenumbers(images)
    return equal_image_grid(images)


def main(dataset, label):
    # to get different samples, use timestamp as seed
    timestamp = time.time()
    seed = int(timestamp * 1000) % 1000000

    shuffled_dataset = DATASETS[dataset].shuffle(buffer_size=10, seed=seed)

    # first get PDF file
    for sample in shuffled_dataset:
        label_column = "label" if "label" in sample else "labels"
        filelabel = _CLASSES[sample[label_column]]
        if label and filelabel != label:
            continue
        pdf_path = sample["file"]
        grid = pdf_to_grid(BytesIO(pdf_path))
        if grid is None:
            continue
        PDF = tempfile.NamedTemporaryFile(suffix=".pdf")
        PDF.write(pdf_path)
        return filelabel, grid, pdf_path


_CLASSES = [
    "letter",
    "form",
    "email",
    "handwritten",
    "advertisement",
    "scientific report",
    "scientific publication",
    "specification",
    "file folder",
    "news article",
    "budget",
    "invoice",
    "presentation",
    "questionnaire",
    "resume",
    "memo",
    "",
]

# load both datasets in memory? --> easier retrieval afterwards with seed index based on pressing button
DATASETS = OrderedDict(
    {
        # "rvl_cdip": load_dataset("bdpc/rvl_cdip_mp", split="test", streaming=True),
        "rvl_cdip_N": load_dataset("bdpc/rvl_cdip_n_mp", split="test", streaming=True),
    }
)

meta_cats = {"dataset": ["rvl_cdip", "rvl_cdip_N"], "label": _CLASSES}
sliders = [gr.Dropdown(choices=choices, value=choices[-1], label=label) for label, choices in meta_cats.items()]
slider_defaults = [sliders[0].value, None]

# test
# l, im, f = main(*slider_defaults)

outputs = [
    gr.Textbox(label="label"),
    gr.Image(label="image grid of PDF"),
    gr.File(label="PDF"),
]

DESCRIPTION = """
Visualize PDF samples from multi-page (PDF) document classification datasets @ https://huggingface.co/datasets/bdpc

- **dataset**: dataset name
- **label**: label name

The first time that the app is launched, it will download the datasets, which can take a few minutes.
For fastest response, choose the rvl_cdip_N dataset, which is considerably smaller to iterate over.
"""

iface = gr.Interface(
    fn=main,
    inputs=sliders,
    outputs=outputs,
    description=DESCRIPTION,
    title="Beyond Document Page Classification: Examples",
)
iface.launch(share=True)