# OCR

# Copyright (C) 2024-2026 Collabora Ltd.

#

# This library is free software; you can redistribute it and/or

# modify it under the terms of the GNU Library General Public

# License as published by the Free Software Foundation; either

# version 2 of the License, or (at your option) any later version.

#

# This library is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

# Library General Public License for more details.

#

# You should have received a copy of the GNU Library General Public

# License along with this library; if not, write to the

# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,

# Boston, MA 02110-1301, USA.

from log.global_logger import GlobalLogger

import backend

CAN_REGISTER_ELEMENT = True

try:

from video_transform import VideoTransform

from utils.format_converter import FormatConverter

from engine.ocr_engine import OcrEngine

from engine.engine_factory import EngineFactory

from backend import GObject

from tasks.ocr import OcrTask

except ImportError as e:

CAN_REGISTER_ELEMENT = False

GlobalLogger().warning(f"The 'ocr' element will not be available. Error {e}")

# Header prefix for OCR text buffer metadata

OCR_META_HEADER = b"GST-OCR:"

class OCRTransform(VideoTransform, OcrTask):

"""

GStreamer element for optical character recognition on video frames.

Set model-name to a HuggingFace model ID, e.g.:

microsoft/trocr-base-printed

When draw-text=True (default), recognized text is drawn directly on the

video frame. OCR results are always appended as a GST-OCR: memory chunk

(JSON with recognized text and regions).

"""

META_HEADER = OCR_META_HEADER

__gstmetadata__ = (

"OCR",

"Transform",

"Optical character recognition using TrOCR on video frames",

"Aaron Boxer <aaron.boxer@collabora.com>",

)

draw_text = GObject.Property(

type=bool,

default=True,

nick="Draw Text",

blurb="Draw recognized text on the video frame",

flags=GObject.ParamFlags.READWRITE,

)

language = GObject.Property(

type=str,

default="en",

nick="Language",

blurb="Language hint for OCR (currently informational)",

flags=GObject.ParamFlags.READWRITE,

)

def __init__(self):

super().__init__()

self.mgr.engine_name = "pyml_ocr_engine"

EngineFactory.register(self.mgr.engine_name, OcrEngine)

self.format_converter = FormatConverter()

@GObject.Property(type=str)

def engine_name(self):

"""Machine Learning Engine (read-only for this element)."""

return self.mgr.engine_name

@engine_name.setter

def engine_name(self, value):

raise ValueError("'engine_name' is read-only for pyml_ocr")

if CAN_REGISTER_ELEMENT and backend.BACKEND == "gst":

__gstelementfactory__ = backend.register_gst_element("pyml_ocr", OCRTransform)

elif not CAN_REGISTER_ELEMENT:

GlobalLogger().warning(

"The 'pyml_ocr' element will not be registered because required modules are missing."

)