pdf/rendering/png_method.py

"""Metodo C — rendering PNG rasterizzato server-side."""

from __future__ import annotations

from pdf.rendering import _raster
from pdf.rendering.base import (
    MethodInfo,
    RenderKind,
    RenderMethod,
    RenderOutput,
    RenderParams,
    boxes_on_page,
)
from pdf.rendering.styles import severity_rgb


class PngRenderMethod(RenderMethod):
    info = MethodInfo(
        key="png",
        label="C · PNG",
        kind=RenderKind.VIEW,
        media_type="image/png",
        styles=("fill", "outline", "label", "pixelate", "blur"),
        default_style="fill",
        description=(
            "Pagina rasterizzata dal server con box disegnati sulla bitmap. "
            "Funziona con qualsiasi PDF; supporta mosaico e sfocatura."
        ),
    )

    def render(self, params: RenderParams) -> RenderOutput:
        import fitz
        import numpy as np

        doc = fitz.open(stream=params.pdf_bytes, filetype="pdf")
        page = doc.load_page(params.page)
        scale = params.dpi / 72.0
        pix = page.get_pixmap(matrix=fitz.Matrix(scale, scale), alpha=False)
        doc.close()

        h, w, n = pix.height, pix.width, pix.n
        arr = np.frombuffer(pix.samples, dtype=np.uint8).reshape(h, w, n).copy()

        for b in boxes_on_page(params):
            x0 = max(0, int(b["x0"] * scale))
            y0 = max(0, int(b["y0"] * scale))
            x1 = min(w, int(b["x1"] * scale))
            y1 = min(h, int(b["y1"] * scale))
            if x1 <= x0 or y1 <= y0:
                continue
            r, g, bl = severity_rgb(b.get("severity", "media"))
            color = np.array([r * 255, g * 255, bl * 255], dtype=np.float32)
            region = arr[y0:y1, x0:x1, :3].astype(np.float32)

            if params.style == "pixelate":
                arr[y0:y1, x0:x1, :3] = _raster.pixelate(region).astype(np.uint8)
            elif params.style == "blur":
                arr[y0:y1, x0:x1, :3] = _raster.box_blur(region).astype(np.uint8)
            elif params.style == "outline":
                _raster.draw_outline(arr, x0, y0, x1, y1, color, thickness=max(2, int(scale)))
            else:  # fill / label
                arr[y0:y1, x0:x1, :3] = _raster.alpha_fill(
                    region, color, params.opacity
                ).astype(np.uint8)

        out_pix = fitz.Pixmap(pix.colorspace, pix.width, pix.height, arr.tobytes(), pix.alpha)
        return RenderOutput(
            data=out_pix.tobytes("png"),
            media_type=self.info.media_type,
            headers={
                "X-Page-Width-Px": str(w),
                "X-Page-Height-Px": str(h),
                "Cache-Control": "private, max-age=300",
            },
        )