app.py

import gradio as gr
import cv2
import numpy as np
from PIL import Image

def flatten_image(img, points):
    if img is None or not points or len(points) != 4:
        return None, "Please click exactly 4 points (TL, TR, BR, BL)."

    image_np = np.array(img)
    h, w = image_np.shape[:2]
    src_pts = np.array(points, dtype=np.float32)

    width_top = np.linalg.norm(src_pts[0] - src_pts[1])
    width_bottom = np.linalg.norm(src_pts[3] - src_pts[2])
    height_left = np.linalg.norm(src_pts[0] - src_pts[3])
    height_right = np.linalg.norm(src_pts[1] - src_pts[2])
    max_width = int(max(width_top, width_bottom))
    max_height = int(max(height_left, height_right))

    dst_pts = np.array([
        [0, 0],
        [max_width - 1, 0],
        [max_width - 1, max_height - 1],
        [0, max_height - 1]
    ], dtype=np.float32)

    M = cv2.getPerspectiveTransform(src_pts, dst_pts)
    warped = cv2.warpPerspective(image_np, M, (max_width, max_height), flags=cv2.INTER_CUBIC)
    return Image.fromarray(warped), None


with gr.Blocks() as demo:
    gr.Markdown("## 📸 Perspective Flatten Tool\nUpload an image, click 4 corners (Top-Left → Top-Right → Bottom-Right → Bottom-Left), then flatten!")

    with gr.Row():
        input_image = gr.Image(label="Upload Image", type="pil")
        output_image = gr.Image(label="Flattened Output")

    coords = gr.State([])

    def collect_points(evt: gr.SelectData, points):
        if points is None:
            points = []
        points.append(evt.index)  # evt.index = (x, y)
        if len(points) > 4:
            points = points[-4:]
        return points, f"Selected {len(points)}/4 points: {points}"

    points_output = gr.Textbox(label="Selected Points", interactive=False)

    # The .select event still works; we just don’t declare tool="select"
    input_image.select(fn=collect_points, inputs=coords, outputs=[coords, points_output])

    flatten_btn = gr.Button("🔄 Flatten Image")
    error_box = gr.Textbox(label="Messages", interactive=False)

    flatten_btn.click(fn=flatten_image, inputs=[input_image, coords], outputs=[output_image, error_box])

    gr.Markdown("Tip: Re-upload image to reset point selection.")

demo.launch()