C# 實現水晶效果頭像生成完整代碼（含縮略、裁剪、渲染）

功能流程

1. 原圖縮略至寬或高 90px
2. 用戶選區裁剪 90×90 區域
3. 套用水晶效果（漸變、陰影、高光）輸出 PNG

核心實現代碼

public static void Avatar(Page page, string filename, int r, int m, int s, int x, int y, bool save, string newAvatarPath)
{
    var imageSrc = Image.FromFile(HttpContext.Current.Server.MapPath("/") + filename);
    int w = imageSrc.Width, h = imageSrc.Height;

    // 旋轉/翻轉參數處理
    if (r == 1 || r == 3) { h = imageSrc.Width; w = imageSrc.Height; }
    if (save) { w = h = 90; }
    if (w > 300) w = 300;
    if (h > 300) h = 300;

    var backColor = Color.DarkTurquoise;
    var size = new Size(w, h);
    var btnBmp = new Bitmap(w, h);
    var g = Graphics.FromImage(btnBmp);

    g.Clear(Color.White);
    g.SmoothingMode = SmoothingMode.AntiAlias;
    g.CompositingQuality = CompositingQuality.HighQuality;
    g.InterpolationMode = InterpolationMode.HighQualityBicubic;

    int btnOff = 0;
    var rc1 = new Rectangle(btnOff, btnOff, size.Width - 1 - btnOff, size.Height - 1 - btnOff);
    var gpath1 = GetGraphicsPath(rc1, 10);
    var gpath1a = GetGraphicsPath(rc1, 15);
    var br1 = new LinearGradientBrush(new Point(0, 0), new Point(0, rc1.Height + 6), backColor, Color.White);

    // 陰影
    int shadowOff = 1;
    var rc2 = rc1; rc2.Offset(0, shadowOff);
    var gpath2 = GetGraphicsPath(rc2, 10);
    var br2 = new PathGradientBrush(gpath2);
    br2.CenterColor = Color.FromArgb(0, 0, 0);
    br2.SurroundColors = new[] { Color.FromArgb(64, 64, 64, 64), Color.FromArgb(64, 128, 128, 128) };

    // 頂部高光
    var rc3 = rc1; rc3.Inflate(-1, -1); rc3.Height = 15;
    var gpath3 = GetGraphicsPath(rc3, 10);
    var br3 = new LinearGradientBrush(rc3, Color.FromArgb(255, Color.White), Color.FromArgb(0, Color.White), LinearGradientMode.Vertical);

    // 繪製順序：陰影 → 底色 → 裁剪區域 → 圖片 → 高光
    if (s > 0) g.FillPath(br2, gpath2);
    if (s > 0) g.FillPath(br1, gpath1);
    g.SetClip(gpath1a, CombineMode.Replace);

    // 圖片變換
    switch (m) {
        case 1: imageSrc.RotateFlip(RotateFlipType.RotateNoneFlipX); break;
        case 2: imageSrc.RotateFlip(RotateFlipType.RotateNoneFlipY); break;
    }
    switch (r) {
        case 1: imageSrc.RotateFlip(RotateFlipType.Rotate90FlipNone); break;
        case 2: imageSrc.RotateFlip(RotateFlipType.Rotate180FlipNone); break;
        case 3: imageSrc.RotateFlip(RotateFlipType.Rotate270FlipNone); break;
    }

    g.DrawImage(imageSrc, -x, -y);
    if (s > 0) g.FillPath(br3, gpath3);

    imageSrc.Dispose(); g.Dispose();

    // 輸出
    using (var ms = new MemoryStream()) {
        btnBmp.Save(ms, ImageFormat.Png);
        if (save) {
            btnBmp.Save(HttpContext.Current.Server.MapPath("/") + newAvatarPath);
        }
        OutputImage(page, ms);
    }
}

private static void OutputImage(Page page, MemoryStream ms) {
    page.Response.Expires = 0;
    page.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);
    page.Response.AddHeader("pragma", "no-cache");
    page.Response.CacheControl = "no-cache";
    page.Response.Clear();
    page.Response.ContentType = "image/png";
    page.Response.BinaryWrite(ms.ToArray());
}

// 輔助：圓角矩形路徑
private static GraphicsPath GetGraphicsPath(Rectangle rect, int radius) {
    var path = new GraphicsPath();
    int d = radius * 2;
    path.AddArc(rect.X, rect.Y, d, d, 180, 90);
    path.AddArc(rect.Right - d, rect.Y, d, d, 270, 90);
    path.AddArc(rect.Right - d, rect.Bottom - d, d, d, 0, 90);
    path.AddArc(rect.X, rect.Bottom - d, d, d, 90, 90);
    path.CloseFigure();
    return path;
}

關鍵技術點

• GraphicsPath + LinearGradientBrush 實現圓角漸變底色
• PathGradientBrush 產生立體陰影效果
• SetClip 限制圖片顯示在圓角區域內
• 高質量插值模式保證縮放清晰度
• 支持旋轉、翻轉、平移參數，配合前端裁剪組件使用