baodan/api/insurance/poster/render_validation.py

"""浏览器合成海报的文件与尺寸校验。"""
import io

from PIL import Image

from insurance.poster.format_registry import list_poster_formats


class PosterRenderValidationError(ValueError):
    """最终海报文件不符合格式契约。"""


def validate_rendered_png(
    image_bytes: bytes,
    format_id: str,
    expected_height: int | None = None,
) -> dict:
    """完整解码 PNG，并验证其真实像素尺寸。"""
    format_spec = next(
        (item for item in list_poster_formats() if item["id"] == format_id),
        None,
    )
    if not format_spec:
        raise PosterRenderValidationError(f"不支持的海报格式: {format_id}")

    try:
        with Image.open(io.BytesIO(image_bytes)) as image:
            image.verify()
        with Image.open(io.BytesIO(image_bytes)) as image:
            image.load()
            width, height = image.size
            image_format = image.format
    except Exception as exc:
        raise PosterRenderValidationError("PNG 文件无法解码或已经损坏") from exc

    if image_format != "PNG":
        raise PosterRenderValidationError("最终海报必须是 PNG 格式")

    expected = format_spec["output"]
    if width != expected["width"]:
        raise PosterRenderValidationError(
            f"海报宽度不匹配，应为 {expected['width']}px，实际为 {width}px"
        )
    if expected["height"] is not None and height != expected["height"]:
        raise PosterRenderValidationError(
            f"海报尺寸不匹配，应为 {expected['width']}×{expected['height']}，"
            f"实际为 {width}×{height}"
        )
    if expected["height"] is None and expected_height is not None and height != expected_height:
        raise PosterRenderValidationError(
            f"长图自定义高度不匹配，应为 {expected['width']}×{expected_height}，"
            f"实际为 {width}×{height}"
        )
    if expected["height"] is None and not 1 <= height <= 32767:
        raise PosterRenderValidationError("长图高度超出浏览器安全范围")

    return {"width": width, "height": height, "format": image_format}