File size: 7,712 Bytes
97b64b9 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 | """Places a preprocessed signature stamp inside (or intentionally near) a target signature box.
Handles aspect-ratio-preserving scale-to-fit, rotation, anchor-based
positioning, sub-pixel offsets, and controlled "misplacement" (an
intentional, probability-gated extra translation used to generate
hard/misaligned samples for benchmarking).
"""
from __future__ import annotations
from dataclasses import dataclass
import cv2
import numpy as np
from src.config.schema import PlacementConfig
from src.utils.geometry_utils import Box
from src.utils.logging_utils import get_logger
from src.utils.random_utils import SeedManager, resolve_scalar_or_range
from src.utils.transform_utils import rotate_and_scale_rgba
logger = get_logger(__name__)
AnchorOffsetFn = "dict[str, callable]"
MIN_SIGNATURE_HEIGHT_PX = 16.0
@dataclass
class PlacementResult:
"""Everything downstream stages need to know about how the signature was placed."""
layer: np.ndarray # full-canvas-sized RGBA layer, transparent outside the signature
target_box: Box
intended_bbox: Box # the signature's transformed bounding box in canvas coordinates
x_offset: float
y_offset: float
rotation_deg: float
scale_factor: float
anchor_point: str
misplaced: bool
misplacement_dx: float
misplacement_dy: float
def _anchor_top_left(anchor: str, box_w: float, box_h: float, sig_w: float, sig_h: float) -> tuple[float, float]:
positions = {
"center": ((box_w - sig_w) / 2.0, (box_h - sig_h) / 2.0),
"top_left": (0.0, 0.0),
"top_right": (box_w - sig_w, 0.0),
"bottom_left": (0.0, box_h - sig_h),
"bottom_right": (box_w - sig_w, box_h - sig_h),
"top_center": ((box_w - sig_w) / 2.0, 0.0),
"bottom_center": ((box_w - sig_w) / 2.0, box_h - sig_h),
"left_center": (0.0, (box_h - sig_h) / 2.0),
"right_center": (box_w - sig_w, (box_h - sig_h) / 2.0),
}
return positions.get(anchor, positions["center"])
class PlacementEngine:
"""Fits, transforms, and positions a signature stamp relative to a target box.
Example:
>>> engine = PlacementEngine(cfg.placement)
>>> result = engine.place(signature_rgba, target_box=(100, 100, 300, 160),
... canvas_size=(1024, 559), seed_manager=sm)
"""
def __init__(self, config: PlacementConfig) -> None:
self.config = config
def place(
self,
signature_rgba: np.ndarray,
target_box: Box,
canvas_size: tuple[int, int],
seed_manager: SeedManager,
) -> PlacementResult:
"""Compute the placed signature layer for one sample.
Args:
signature_rgba: The tightly-cropped RGBA signature stamp from
:class:`~src.rendering.signature_preprocessor.SignaturePreprocessor`.
target_box: The ``(x1, y1, x2, y2)`` target signature field, in
canvas pixel coordinates.
canvas_size: ``(width, height)`` of the full document canvas.
seed_manager: Per-sample deterministic RNG provider.
Returns:
A :class:`PlacementResult` with the full-canvas RGBA layer ready
for blending, plus every resolved placement parameter for
metadata export.
"""
cfg = self.config
rng = seed_manager.numpy_rng("placement")
canvas_w, canvas_h = canvas_size
rotation_deg = resolve_scalar_or_range(cfg.rotation_deg, rng)
scale_factor = resolve_scalar_or_range(cfg.scale_factor, rng)
x_offset = resolve_scalar_or_range(cfg.x_offset, rng)
y_offset = resolve_scalar_or_range(cfg.y_offset, rng)
x1, y1, x2, y2 = target_box
box_w, box_h = (x2 - x1), (y2 - y1)
margin_x, margin_y = box_w * cfg.margin, box_h * cfg.margin
inner_x1, inner_y1 = x1 + margin_x, y1 + margin_y
inner_w = max(box_w - 2 * margin_x, 1.0)
inner_h = max(box_h - 2 * margin_y, 1.0)
rotated = rotate_and_scale_rgba(signature_rgba, rotation_deg, 1.0)
sig_h, sig_w = rotated.shape[:2]
fit_scale = min(inner_w / max(sig_w, 1), inner_h / max(sig_h, 1))
final_scale = max(fit_scale * scale_factor, 1e-3)
# Never let the signature shrink below a legible minimum height, even
# inside a very short box (real "sign here" lines are often only
# 12-20px tall at document resolution) -- a genuinely tiny box should
# make the signature overflow it, not vanish into sub-pixel noise.
min_height_scale = MIN_SIGNATURE_HEIGHT_PX / max(sig_h, 1)
final_scale = max(final_scale, min_height_scale)
placed = cv2.resize(
rotated, (max(int(round(sig_w * final_scale)), 1), max(int(round(sig_h * final_scale)), 1)),
interpolation=cv2.INTER_AREA if final_scale < 1.0 else cv2.INTER_CUBIC,
)
placed_h, placed_w = placed.shape[:2]
ax, ay = _anchor_top_left(cfg.anchor_point, inner_w, inner_h, placed_w, placed_h)
base_x = inner_x1 + ax + x_offset
base_y = inner_y1 + ay + y_offset
misplaced = bool(rng.uniform(0.0, 1.0) < cfg.misplacement_probability)
misplacement_dx = misplacement_dy = 0.0
if misplaced:
strength = resolve_scalar_or_range(cfg.misplacement_strength, rng)
max_shift = strength * max(box_w, box_h)
angle = rng.uniform(0, 2 * np.pi)
radius = rng.uniform(0.3, 1.0) * max_shift
misplacement_dx = float(np.cos(angle) * radius)
misplacement_dy = float(np.sin(angle) * radius)
final_x = base_x + misplacement_dx
final_y = base_y + misplacement_dy
if not cfg.allow_partial_outside and not misplaced:
final_x = float(np.clip(final_x, inner_x1, inner_x1 + max(inner_w - placed_w, 0)))
final_y = float(np.clip(final_y, inner_y1, inner_y1 + max(inner_h - placed_h, 0)))
# Hard safety clamp: never let the signature drift entirely off the physical page.
final_x = float(np.clip(final_x, -placed_w * 0.6, canvas_w - placed_w * 0.4))
final_y = float(np.clip(final_y, -placed_h * 0.6, canvas_h - placed_h * 0.4))
layer = np.zeros((canvas_h, canvas_w, 4), dtype=np.uint8)
self._paste(layer, placed, int(round(final_x)), int(round(final_y)))
intended_bbox: Box = (final_x, final_y, final_x + placed_w, final_y + placed_h)
return PlacementResult(
layer=layer,
target_box=target_box,
intended_bbox=intended_bbox,
x_offset=x_offset,
y_offset=y_offset,
rotation_deg=rotation_deg,
scale_factor=scale_factor,
anchor_point=cfg.anchor_point,
misplaced=misplaced,
misplacement_dx=misplacement_dx,
misplacement_dy=misplacement_dy,
)
@staticmethod
def _paste(canvas: np.ndarray, sprite: np.ndarray, x: int, y: int) -> None:
"""Alpha-aware paste of ``sprite`` onto ``canvas`` at ``(x, y)``, clipped to bounds."""
canvas_h, canvas_w = canvas.shape[:2]
sprite_h, sprite_w = sprite.shape[:2]
dst_x1, dst_y1 = max(x, 0), max(y, 0)
dst_x2, dst_y2 = min(x + sprite_w, canvas_w), min(y + sprite_h, canvas_h)
if dst_x2 <= dst_x1 or dst_y2 <= dst_y1:
logger.warning("Placed signature falls entirely outside the canvas; skipping paste.")
return
src_x1, src_y1 = dst_x1 - x, dst_y1 - y
src_x2, src_y2 = src_x1 + (dst_x2 - dst_x1), src_y1 + (dst_y2 - dst_y1)
canvas[dst_y1:dst_y2, dst_x1:dst_x2] = sprite[src_y1:src_y2, src_x1:src_x2]
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