fis_lib_measure/lib/view/vid_painter/carotid_vid_painter.dart

import 'package:flutter/material.dart';
import 'dart:ui' as ui;

class CarotidVidPainter extends CustomPainter {
  CarotidVidPainter({required this.image, this.stdSize = const Size(599, 400)});
  ui.Image image;
  Size stdSize;

  @override
  void paint(Canvas canvas, Size size) async {
    canvas.save();
    final double stdScaleX = size.width / stdSize.width;
    final double stdScaleY = size.height / stdSize.height;
    final double stdScale = stdScaleX < stdScaleY ? stdScaleX : stdScaleY;
    final double scaleX = size.width / image.width;
    final double scaleY = size.height / image.height;
    final double scale = scaleX < scaleY ? scaleX : scaleY;
    bool needScale =
        image.width < stdSize.width && image.height < stdSize.height;
    final double finalScale = needScale ? stdScale : scale;
    final double offsetX = (size.width - image.width * finalScale) / 2;
    final double offsetY = (size.height - image.height * finalScale) / 2;
    canvas.drawImageRect(
        image,
        Rect.fromLTWH(0, 0, image.width.toDouble(), image.height.toDouble()),
        Rect.fromLTWH(offsetX, offsetY, image.width * finalScale,
            image.height * finalScale),
        Paint());
    // 小图像绘制一圈蓝色轮廓
    if (needScale) {
      canvas.drawRect(
          Rect.fromLTWH(offsetX, offsetY, image.width * finalScale,
              image.height * finalScale),
          Paint()
            ..color = Colors.blue
            ..strokeWidth = 1
            ..style = PaintingStyle.stroke);
    }

    canvas.restore();
  }

  @override
  bool shouldRepaint(covariant CarotidVidPainter oldDelegate) {
    return true;
  }
}