using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Lskj.Main.Control
{
    public partial class BackgroundPanel :Panel
    {
        private Image _originalBackgroundImage;

        // 公开属性：设置/获取背景图片
        public Image BackgroundImageCustom
        {
            get => _originalBackgroundImage;
            set
            {
                _originalBackgroundImage = value;
                Invalidate(); // 设置图片后立即重绘
            }
        }

        public BackgroundPanel()
        {
            // 关键设置：关闭Panel默认背景，启用双缓冲减少闪烁
            this.BackgroundImage = null;
            this.DoubleBuffered = true;
            this.SetStyle(ControlStyles.UserPaint |
                           ControlStyles.AllPaintingInWmPaint |
                           ControlStyles.OptimizedDoubleBuffer, true);
        }

        // 重写OnPaint方法，手动绘制背景图
        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);

            // 图片为空时直接返回
            if (_originalBackgroundImage == null) return;

            // 1. 计算等比缩放比例（以Panel的ClientSize为基准）
            float scaleX = (float)this.ClientSize.Width / _originalBackgroundImage.Width;
            float scaleY = (float)this.ClientSize.Height / _originalBackgroundImage.Height;
            float scale = Math.Min(scaleX, scaleY); // 取较小值，避免图片超出Panel

            // 2. 计算图片绘制的位置（居中显示）
            int newWidth = (int)(_originalBackgroundImage.Width * scale);
            int newHeight = (int)(_originalBackgroundImage.Height * scale);
            int x = (this.ClientSize.Width - newWidth) / 2;
            int y = (this.ClientSize.Height - newHeight) / 2;

            // 3. 高质量绘制图片（抗锯齿、高清缩放）
            e.Graphics.SmoothingMode = SmoothingMode.HighQuality;
            e.Graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
            e.Graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
            e.Graphics.DrawImage(_originalBackgroundImage, new Rectangle(x, y, newWidth, newHeight));
        }

        // Panel大小变化时触发重绘
        protected override void OnResize(EventArgs e)
        {
            base.OnResize(e);
            Invalidate(); // 标记控件需要重绘
        }


    }
}