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meme-search-engine/ocr.py
osmarks 7cb42e028f Rewrite entire application (well, backend) in Rust and also Go
I decided I wanted to integrate the experimental OCR thing better, so I rewrote in Go and also integrated the thumbnailer.
However, Go is a bad langauge and I only used it out of spite.
It turned out to have a very hard-to-fix memory leak due to some unclear interaction between libvips and both sets of bindings I tried, so I had Claude-3 transpile it to Rust then spent a while fixing the several mistakes it made and making tweaks.
The new Rust version works, although I need to actually do something with the OCR data and make the index queryable concurrently.
2024-05-21 00:09:04 +01:00

101 lines
4.3 KiB
Python

import pyjson5
import re
import asyncio
import aiohttp
from PIL import Image
import time
import io
CALLBACK_REGEX = re.compile(r">AF_initDataCallback\(({key: 'ds:1'.*?)\);</script>")
def encode_img(img):
image_bytes = io.BytesIO()
img.save(image_bytes, format="PNG", compress_level=6)
return image_bytes.getvalue()
def rationalize_coords_format1(image_w, image_h, center_x_fraction, center_y_fraction, width_fraction, height_fraction, mysterious):
return {
"x": round((center_x_fraction - width_fraction / 2) * image_w),
"y": round((center_y_fraction - height_fraction / 2) * image_h),
"w": round(width_fraction * image_w),
"h": round(height_fraction * image_h)
}
async def scan_image_chunk(sess, image):
timestamp = int(time.time() * 1000)
url = f"https://lens.google.com/v3/upload?stcs={timestamp}"
headers = {"User-Agent": "Mozilla/5.0 (Linux; Android 13; RMX3771) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.6167.144 Mobile Safari/537.36"}
cookies = {"SOCS": "CAESEwgDEgk0ODE3Nzk3MjQaAmVuIAEaBgiA_LyaBg"}
# send data to inscrutable undocumented Google service
# https://github.com/AuroraWright/owocr/blob/master/owocr/ocr.py#L193
async with aiohttp.ClientSession() as sess:
data = aiohttp.FormData()
data.add_field(
"encoded_image",
encode_img(image),
filename="ocr" + str(timestamp) + ".png",
content_type="image/png"
)
async with sess.post(url, headers=headers, cookies=cookies, data=data, timeout=10) as res:
body = await res.text()
# I really worry about Google sometimes. This is not a sensible format.
match = CALLBACK_REGEX.search(body)
if match == None:
raise ValueError("Invalid callback")
lens_object = pyjson5.loads(match.group(1))
if "errorHasStatus" in lens_object:
raise RuntimeError("Lens failed")
text_segments = []
text_regions = []
root = lens_object["data"]
# I don't know why Google did this.
# Text segments are in one place and their locations are in another, using a very strange coordinate system.
# At least I don't need whatever is contained in the base64 parts (which I assume are protobufs).
# TODO: on a few images, this seems to not work for some reason.
try:
text_segments = root[3][4][0][0]
text_regions = [ rationalize_coords_format1(image.width, image.height, *x[1]) for x in root[2][3][0] if x[11].startswith("text:") ]
except (KeyError, IndexError):
# https://github.com/dimdenGD/chrome-lens-ocr/blob/main/src/core.js#L316 has code for a fallback text segment read mode.
# In testing, this proved unnecessary (quirks of the HTTP request? I don't know), and this only happens on textless images.
return [], []
return text_segments, text_regions
MAX_SCAN_DIM = 1000 # not actually true but close enough
def chunk_image(image: Image):
chunks = []
# Cut image down in X axis (I'm assuming images aren't too wide to scan in downscaled form because merging text horizontally would be annoying)
if image.width > MAX_SCAN_DIM:
image = image.resize((MAX_SCAN_DIM, round(image.height * (image.width / MAX_SCAN_DIM))), Image.LANCZOS)
for y in range(0, image.height, MAX_SCAN_DIM):
chunks.append(image.crop((0, y, image.width, min(y + MAX_SCAN_DIM, image.height))))
return chunks
async def scan_chunks(sess: aiohttp.ClientSession, chunks: [Image]):
# If text happens to be split across the cut line it won't get read.
# This is because doing overlap read areas would be really annoying.
text = ""
regions = []
for chunk in chunks:
new_segments, new_regions = await scan_image_chunk(sess, chunk)
for segment in new_segments:
text += segment + "\n"
for i, (segment, region) in enumerate(zip(new_segments, new_regions)):
regions.append({ **region, "y": region["y"] + (MAX_SCAN_DIM * i), "text": segment })
return text, regions
async def scan_image(sess: aiohttp.ClientSession, image: Image):
return await scan_chunks(sess, chunk_image(image))
if __name__ == "__main__":
async def main():
async with aiohttp.ClientSession() as sess:
print(await scan_image(sess, Image.open("/data/public/memes-or-something/linear-algebra-chess.png")))
asyncio.run(main())