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import logging
import math
import cv2
import gradio as gr
import numpy as np
import onnxruntime as ort
from PIL import Image, ImageOps
logging.basicConfig(format="%(asctime)s - %(name)s - %(levelname)s - %(message)s")
MODEL_PATH = "model.onnx"
IMAGE_SIZE = 480
SESSION = ort.InferenceSession(MODEL_PATH)
INPUT_NAME = SESSION.get_inputs()[0].name
def preprocess(img: Image.Image) -> np.ndarray:
resized_img = ImageOps.pad(img, (IMAGE_SIZE, IMAGE_SIZE), centering=(0, 0))
img_chw = np.array(resized_img).transpose(2, 0, 1).astype(np.float32) / 255
img_chw = (img_chw - 0.5) / 0.5
return img_chw
def distance(p1, p2):
return ((p1[0] - p2[0]) ** 2 + (p1[1] - p2[1]) ** 2) ** 0.5
# https://stackoverflow.com/a/1222855
# https://www.microsoft.com/en-us/research/wp-content/uploads/2016/11/Digital-Signal-Processing.pdf
def get_aspect_ratio_zhang(keypoints: np.ndarray, img_width: int, img_height: int):
keypoints = keypoints[[3, 2, 0, 1]] # re-arrange keypoint according to Zhang 2006 Figure 6
keypoints = np.concatenate([keypoints, np.ones((4, 1))], axis=1) # convert to homogeneous coordinates
# equation (11) and (12)
k2 = np.cross(keypoints[0], keypoints[3]).dot(keypoints[2]) / np.cross(keypoints[1], keypoints[3]).dot(keypoints[2])
k3 = np.cross(keypoints[0], keypoints[3]).dot(keypoints[1]) / np.cross(keypoints[2], keypoints[3]).dot(keypoints[1])
# equation (14) and (16)
n2 = k2 * keypoints[1] - keypoints[0]
n3 = k3 * keypoints[2] - keypoints[0]
# equation (21)
u0 = img_width / 2
v0 = img_height / 2
f2 = -(n2[0] * n3[0] - (n2[0] * n3[2] + n2[2] + n3[0]) * u0 + n2[2] * n3[2] * u0 * u0) / (n2[2] * n3[2]) + (
n2[1] * n3[1] - (n2[1] * n3[2] + n2[2] * n3[1]) * v0 + n2[2] * n3[2] * v0 * v0
)
f = math.sqrt(f2)
# equation (20)
A = np.array([[f, 0, u0], [0, f, v0], [0, 0, 1]])
A_inv = np.linalg.inv(A)
mid = A_inv.T.dot(A_inv)
wh_ratio2 = n2.dot(mid).dot(n2) / n3.dot(mid).dot(n3)
return math.sqrt(wh_ratio2)
def rectify(img_np: np.ndarray, keypoints: np.ndarray):
img_height, img_width = img_np.shape[:2]
h1 = distance(keypoints[0], keypoints[3])
h2 = distance(keypoints[1], keypoints[2])
h = (h1 + h2) * 0.5
# this may fail if two lines are parallel
try:
wh_ratio = get_aspect_ratio_zhang(keypoints, img_width, img_height)
w = h * wh_ratio
except:
logging.exception("Failed to estimate aspect ratio from perspective")
w1 = distance(keypoints[0], keypoints[1])
w2 = distance(keypoints[3], keypoints[2])
w = (w1 + w2) * 0.5
target_kpts = np.array([[1, 1], [w + 1, 1], [w + 1, h + 1], [1, h + 1]], dtype=np.float32)
transform = cv2.getPerspectiveTransform(keypoints, target_kpts)
cropped = cv2.warpPerspective(img_np, transform, (round(w) + 2, round(h) + 2), flags=cv2.INTER_CUBIC)
return cropped
def predict(img: Image.Image):
img_chw = preprocess(img)
pred_kpts = SESSION.run(None, {INPUT_NAME: img_chw[None]})[0][0]
kpts_xy = pred_kpts[:, :2] * max(img.size) / IMAGE_SIZE
img_np = np.array(img)
cv2.polylines(
img_np,
[kpts_xy.astype(int)],
True,
(0, 255, 0),
thickness=5,
lineType=cv2.LINE_AA,
)
if (pred_kpts[:, 2] >= 0.25).all():
cropped = rectify(np.array(img), kpts_xy)
else:
cropped = None
return cropped, img_np
gr.Interface(
predict,
inputs=[gr.Image(type="pil")],
outputs=["image", "image"],
examples=["estonia_id_card.jpg", "german_bundesdruckerei_passport.webp"],
).launch(server_name="0.0.0.0")
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