app.py

import matplotlib.pyplot as plt
import matplotlib.patches as patches
from matplotlib.patches import Patch
import io
from PIL import Image, ImageDraw
import numpy as np
import csv
import pandas as pd

from transformers import TableTransformerImageProcessor, AutoModelForObjectDetection
import torch

import easyocr

import gradio as gr

# load table detection model
processor = TableTransformerImageProcessor(max_size=800)
model = AutoModelForObjectDetection.from_pretrained("microsoft/table-transformer-detection", revision="no_timm")

# load table structure recognition model
structure_processor = TableTransformerImageProcessor(max_size=1000)
structure_model = AutoModelForObjectDetection.from_pretrained("microsoft/table-structure-recognition-v1.1-all")

# load EasyOCR reader
reader = easyocr.Reader(['en'])


# for output bounding box post-processing
def box_cxcywh_to_xyxy(x):
    x_c, y_c, w, h = x.unbind(-1)
    b = [(x_c - 0.5 * w), (y_c - 0.5 * h), (x_c + 0.5 * w), (y_c + 0.5 * h)]
    return torch.stack(b, dim=1)


def rescale_bboxes(out_bbox, size):
    width, height = size
    boxes = box_cxcywh_to_xyxy(out_bbox)
    boxes = boxes * torch.tensor([width, height, width, height], dtype=torch.float32)
    return boxes


def outputs_to_objects(outputs, img_size, id2label):
    m = outputs.logits.softmax(-1).max(-1)
    pred_labels = list(m.indices.detach().cpu().numpy())[0]
    pred_scores = list(m.values.detach().cpu().numpy())[0]
    pred_bboxes = outputs['pred_boxes'].detach().cpu()[0]
    pred_bboxes = [elem.tolist() for elem in rescale_bboxes(pred_bboxes, img_size)]

    objects = []
    for label, score, bbox in zip(pred_labels, pred_scores, pred_bboxes):
        class_label = id2label[int(label)]
        if not class_label == 'no object':
            objects.append({'label': class_label, 'score': float(score),
                            'bbox': [float(elem) for elem in bbox]})

    return objects


def fig2img(fig):
    """Convert a Matplotlib figure to a PIL Image and return it"""
    buf = io.BytesIO()
    fig.savefig(buf)
    buf.seek(0)
    image = Image.open(buf)
    return image


def visualize_detected_tables(img, det_tables):
    plt.imshow(img, interpolation="lanczos")
    fig = plt.gcf()
    fig.set_size_inches(20, 20)
    ax = plt.gca()

    for det_table in det_tables:
        bbox = det_table['bbox']

        if det_table['label'] == 'table':
            facecolor = (1, 0, 0.45)
            edgecolor = (1, 0, 0.45)
            alpha = 0.3
            linewidth = 2
            hatch='//////'
        elif det_table['label'] == 'table rotated':
            facecolor = (0.95, 0.6, 0.1)
            edgecolor = (0.95, 0.6, 0.1)
            alpha = 0.3
            linewidth = 2
            hatch='//////'
        else:
            continue

        rect = patches.Rectangle(bbox[:2], bbox[2]-bbox[0], bbox[3]-bbox[1], linewidth=linewidth,
                                    edgecolor='none',facecolor=facecolor, alpha=0.1)
        ax.add_patch(rect)
        rect = patches.Rectangle(bbox[:2], bbox[2]-bbox[0], bbox[3]-bbox[1], linewidth=linewidth,
                                    edgecolor=edgecolor,facecolor='none',linestyle='-', alpha=alpha)
        ax.add_patch(rect)
        rect = patches.Rectangle(bbox[:2], bbox[2]-bbox[0], bbox[3]-bbox[1], linewidth=0,
                                    edgecolor=edgecolor,facecolor='none',linestyle='-', hatch=hatch, alpha=0.2)
        ax.add_patch(rect)

    plt.xticks([], [])
    plt.yticks([], [])

    legend_elements = [Patch(facecolor=(1, 0, 0.45), edgecolor=(1, 0, 0.45),
                                label='Table', hatch='//////', alpha=0.3),
                        Patch(facecolor=(0.95, 0.6, 0.1), edgecolor=(0.95, 0.6, 0.1),
                                label='Table (rotated)', hatch='//////', alpha=0.3)]
    plt.legend(handles=legend_elements, bbox_to_anchor=(0.5, -0.02), loc='upper center', borderaxespad=0,
                    fontsize=10, ncol=2)
    plt.gcf().set_size_inches(10, 10)
    plt.axis('off')

    return fig


def detect_and_crop_table(image):
    # prepare image for the model
    pixel_values = processor(image, return_tensors="pt").pixel_values

    # forward pass
    with torch.no_grad():
        outputs = model(pixel_values)

    # postprocess to get detected tables
    id2label = model.config.id2label
    id2label[len(model.config.id2label)] = "no object"
    detected_tables = outputs_to_objects(outputs, image.size, id2label)

    # visualize
    # fig = visualize_detected_tables(image, detected_tables)
    # image = fig2img(fig)

    # crop first detected table out of image
    cropped_table = image.crop(detected_tables[0]["bbox"])

    return cropped_table


def recognize_table(image):
    # prepare image for the model
    pixel_values = structure_processor(images=image, return_tensors="pt").pixel_values

    # forward pass
    with torch.no_grad():
        outputs = structure_model(pixel_values)

    # postprocess to get individual elements
    id2label = structure_model.config.id2label
    id2label[len(structure_model.config.id2label)] = "no object"
    cells = outputs_to_objects(outputs, image.size, id2label)

    # visualize cells on cropped table
    draw = ImageDraw.Draw(image)

    for cell in cells:
        draw.rectangle(cell["bbox"], outline="red")
        
    return image, cells


def get_cell_coordinates_by_row(table_data):
    # Extract rows and columns
    rows = [entry for entry in table_data if entry['label'] == 'table row']
    columns = [entry for entry in table_data if entry['label'] == 'table column']

    # Sort rows and columns by their Y and X coordinates, respectively
    rows.sort(key=lambda x: x['bbox'][1])
    columns.sort(key=lambda x: x['bbox'][0])

    # Function to find cell coordinates
    def find_cell_coordinates(row, column):
        cell_bbox = [column['bbox'][0], row['bbox'][1], column['bbox'][2], row['bbox'][3]]
        return cell_bbox

    # Generate cell coordinates and count cells in each row
    cell_coordinates = []

    for row in rows:
        row_cells = []
        for column in columns:
            cell_bbox = find_cell_coordinates(row, column)
            row_cells.append({'column': column['bbox'], 'cell': cell_bbox})

        # Sort cells in the row by X coordinate
        row_cells.sort(key=lambda x: x['column'][0])

        # Append row information to cell_coordinates
        cell_coordinates.append({'row': row['bbox'], 'cells': row_cells, 'cell_count': len(row_cells)})

    # Sort rows from top to bottom
    cell_coordinates.sort(key=lambda x: x['row'][1])

    return cell_coordinates


def apply_ocr(cell_coordinates, cropped_table):
    # let's OCR row by row
    data = dict()
    max_num_columns = 0
    for idx, row in enumerate(cell_coordinates):
      row_text = []
      for cell in row["cells"]:
        # crop cell out of image
        cell_image = np.array(cropped_table.crop(cell["cell"]))
        # apply OCR
        result = reader.readtext(np.array(cell_image))
        if len(result) > 0:
          text = " ".join([x[1] for x in result])
          row_text.append(text)

      if len(row_text) > max_num_columns:
          max_num_columns = len(row_text)
      
      data[idx] = row_text

    # pad rows which don't have max_num_columns elements
    # to make sure all rows have the same number of columns
    for row, row_data in data.copy().items():
        if len(row_data) != max_num_columns:
          row_data = row_data + ["" for _ in range(max_num_columns - len(row_data))]
        data[row] = row_data

    # write to csv
    with open('output.csv','w') as result_file:
        wr = csv.writer(result_file, dialect='excel')
    
        for row, row_text in data.items():
            wr.writerow(row_text)

    # return as Pandas dataframe
    df = pd.read_csv('output.csv')

    return df


def process_pdf(image):
    cropped_table = detect_and_crop_table(image)

    image, cells = recognize_table(cropped_table)

    cell_coordinates = get_cell_coordinates_by_row(cells)

    data = apply_ocr(cell_coordinates, image)

    return image, data
    

title = "Demo: table detection & recognition with Table Transformer"
description = "Demo for table extraction with the Table Transformer (TATR)."
examples = [['image.png', 'clip_paper.png']]

app = gr.Interface(fn=process_pdf, 
                     inputs=gr.Image(type="pil"), 
                     outputs=[gr.Image(type="pil", label="Detected table"), gr.Dataframe(label="Table as CSV")],
                     title=title,
                     description=description,
                     examples=examples)
app.queue()
app.launch(debug=True)