gsv-ocr-check

A Python library for verifying Google Street View panorama existence and calibrating OCR bounding boxes through perspective re-projection.

Features

• Panorama Existence Check: Verify whether a Google Street View panorama ID is still accessible
• Panorama Download: Download panoramas to disk or into memory as PIL Images
• OCR Bounding Box Calibration: Refine OCR coordinates by re-running OCR on perspective crops at multiple fields of view
• Engine Agnostic: Works with any panoocr-compatible OCR engine
• Async Support: Both sync and async APIs for panorama operations

Installation

Install the base package:

pip install gsv-ocr-check

Install with macOS OCR support:

pip install "gsv-ocr-check[macocr]"

Using uv (recommended):

uv add gsv-ocr-check
uv add "gsv-ocr-check[macocr]"

Quick Start

from gsv_ocr_check import check_panorama_exists, calibrate_ocr, download_panorama
from panoocr.engines.macocr import MacOCREngine

# 1. Check if a panorama still exists on Google Street View
exists = check_panorama_exists("abc123")

# 2. Download the panorama
image = download_panorama("abc123", output_path="pano.jpg")

# 3. Calibrate an OCR bounding box
engine = MacOCREngine()
result = calibrate_ocr(
    panorama="pano.jpg",
    target_text="LOVE",
    yaw=38.5,
    pitch=-2.4,
    engine=engine,
)

if result:
    print(f"Text: {result.text}")
    print(f"Position: yaw={result.yaw:.2f}°, pitch={result.pitch:.2f}°")
    print(f"Size: {result.width:.2f}° x {result.height:.2f}°")
    print(f"Confidence: {result.confidence}")
    print(f"FOV used: {result.fov_used}°")

API

Panorama Operations

check_panorama_exists(panorama_id) -> bool

Check if a Google Street View panorama still exists. Returns True if accessible, False otherwise.

from gsv_ocr_check import check_panorama_exists

if check_panorama_exists("UVfBLpzNhpZdImXJqozDmg"):
    print("Panorama is still available")

download_panorama(panorama_id, output_path=None, zoom=5, quality=95) -> Image | None

Download a panorama image. Returns a PIL Image, or None if the panorama is not found.

from gsv_ocr_check import download_panorama

# Download to memory only
image = download_panorama("abc123")

# Download and save to disk
image = download_panorama("abc123", output_path="panoramas/abc123.jpg")

# Download at lower resolution (zoom 0-5)
image = download_panorama("abc123", zoom=2)

Async Variants

Both functions have async counterparts for use in async contexts:

from gsv_ocr_check import check_panorama_exists_async, download_panorama_async

exists = await check_panorama_exists_async("abc123")
image = await download_panorama_async("abc123", output_path="pano.jpg")

OCR Calibration

calibrate_ocr(panorama, target_text, yaw, pitch, engine, **kwargs) -> CalibrationResult | None

Refine an OCR bounding box by generating perspective views centered on the original detection, re-running OCR, and returning the best match in spherical coordinates.

from gsv_ocr_check import calibrate_ocr
from panoocr.engines.macocr import MacOCREngine

engine = MacOCREngine()
result = calibrate_ocr(
    panorama="pano.jpg",       # path or PIL Image
    target_text="LOVE",        # exact match, case-insensitive
    yaw=38.5,                  # original detection yaw
    pitch=-2.4,                # original detection pitch
    engine=engine,             # any panoocr-compatible engine
)

Parameters:

CalibrationResult

Dataclass returned by calibrate_ocr with the refined detection:

@dataclass
class CalibrationResult:
    text: str              # Matched text
    confidence: float      # OCR confidence score
    yaw: float             # Refined yaw in degrees
    pitch: float           # Refined pitch in degrees
    width: float           # Angular width in degrees
    height: float          # Angular height in degrees
    engine: str            # OCR engine class name
    match_type: str        # "exact"
    original_yaw: float    # Input yaw (preserved)
    original_pitch: float  # Input pitch (preserved)
    fov_used: float        # FOV that produced the match
    resolution_used: int   # Resolution used

How Calibration Works

1. Load the equirectangular panorama image
2. Generate a perspective view centered on the original yaw/pitch coordinates
3. Try multiple FOVs in sequence (default: 45° → 90° → 120°) — narrow FOV gives better resolution, wider FOV captures more context
4. Run OCR on each perspective image
5. Filter for exact text matches (case-insensitive)
6. Select the match closest to the image center
7. Transform pixel coordinates back to spherical using panoocr.geometry.perspective_to_sphere
8. Return the first successful match, or None if no match at any FOV

Advanced Usage

Custom OCR Engine

Any object with a recognize(pil_image) method returning results with .text, .confidence, and .bounding_box attributes works:

from panoocr.engines.easyocr import EasyOCREngine

engine = EasyOCREngine(config={"language_preference": ["en"]})
result = calibrate_ocr("pano.jpg", "HELLO", yaw=0, pitch=0, engine=engine)

Saving Perspective Crops

Save the perspective images generated during calibration for debugging:

result = calibrate_ocr(
    panorama="pano.jpg",
    target_text="LOVE",
    yaw=38.5,
    pitch=-2.4,
    engine=engine,
    save_perspectives="debug/perspectives/",
)
# Saves: debug/perspectives/<pano_id>_fov45.jpg, etc.

Custom FOVs and Resolution

result = calibrate_ocr(
    panorama="pano.jpg",
    target_text="LOVE",
    yaw=38.5,
    pitch=-2.4,
    engine=engine,
    fovs=[30.0, 60.0, 90.0],  # custom FOV sequence
    resolution=4096,            # higher resolution perspective
)

Using PIL Images Directly

from PIL import Image

image = Image.open("pano.jpg")
result = calibrate_ocr(
    panorama=image,
    target_text="LOVE",
    yaw=38.5,
    pitch=-2.4,
    engine=engine,
    panorama_id="my_pano",  # required when passing PIL Image
)

Coordinate System

All coordinates use spherical (yaw, pitch) format:

• Yaw: Horizontal angle in degrees, normalized to [-180, 180]
• Pitch: Vertical angle in degrees (-90 to 90)
• Width/Height: Angular dimensions in degrees

Dependencies

• streetlevel — Google Street View panorama access
• panoocr — Perspective projection, coordinate transforms, OCR engines
• Pillow — Image handling

License

MIT License — see LICENSE for details.