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C# 等比压缩图片，返回固定大小并居中

等比压缩图片，返回固定大小并居中，如果图片不是正方形，周围就是空白。

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/// <summary>
/// 等比压缩图片，返回固定大小并居中
/// </summary>
/// <param name="mg"></param>
/// <param name="newSize"></param>
/// <returns></returns>
public static Bitmap ResizeImage(Bitmap mg, Size newSize)
{
    double ratio;//压缩比
    int myWidth;
    int myHeight;
    int x = 0;
    int y = 0;
    if ((mg.Width / Convert.ToDouble(newSize.Width)) > (mg.Height / Convert.ToDouble(newSize.Height)))
        ratio = Convert.ToDouble(mg.Width) / Convert.ToDouble(newSize.Width);
    else
        ratio = Convert.ToDouble(mg.Height) / Convert.ToDouble(newSize.Height);
    myHeight = (int)Math.Ceiling(mg.Height / ratio);
    myWidth = (int)Math.Ceiling(mg.Width / ratio);
    Bitmap bp = new Bitmap(newSize.Width, newSize.Height);
    x = (newSize.Width - myWidth) / 2;
    y = (newSize.Height - myHeight) / 2;
    System.Drawing.Graphics g = Graphics.FromImage(bp);
    g.SmoothingMode = SmoothingMode.HighQuality;
    g.InterpolationMode = InterpolationMode.HighQualityBicubic;
    g.PixelOffsetMode = PixelOffsetMode.HighQuality;
    Rectangle rect = new Rectangle(x, y, myWidth, myHeight);
    g.DrawImage(mg, rect, 0, 0, mg.Width, mg.Height, GraphicsUnit.Pixel);
    return bp;
}
CSharp