获取一个图片按等比例缩小后的大小代码,Asp.Net代码库,德仔网

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【Asp.Net】获取一个图片按等比例缩小后的大小

作者:Dezai.CN / 发布于2012/12/11/ 675

/// <summary>
/// 获取一个图片按等比例缩小后的大小。
/// </summary>
/// <param name="maxWidth">需要缩小到的宽度</param>
/// <param name="maxHeight">需要缩小到的高度</param>
/// <param name="imageOriginalWidth">图片的原始宽度</param>
/// <param name="imageOriginalHeight">图片的原始高度</param>
/// <returns>返回图片按等比例缩小后的实际大小</returns>
public static Size GetNewSize(int maxWidth, int maxHeight, int imageOriginalWidth, int imageOriginalHeight)
{
    double w = 0.0;
    double h = 0.0;
    double sw = Convert.ToDouble(imageOriginalWidth);
    double sh = Convert.ToDouble(imageOriginalHeight);
    double mw = Convert.ToDouble(maxWidth);
    double mh = Convert.ToDouble(maxHeight);
    if (sw < mw && sh < mh)
    {
        w = sw;
        h = sh;
    }
    else if ((sw / sh) > (mw / mh))
    {
        w = maxWidth;
        h = (w * sh) / sw;
    }
    else
    {
        h = maxHeight;
        w = (h * sw) / sh;
    }
    return new Size(Convert.ToInt32(w), Convert.ToInt32(h));
}
/// <summary>
/// 对给定的一个图片（Image对象）生成一个指定大小的缩略图。
/// </summary>
/// <param name="originalImage">原始图片</param>
/// <param name="thumMaxWidth">缩略图的宽度</param>
/// <param name="thumMaxHeight">缩略图的高度</param>
/// <returns>返回缩略图的Image对象</returns>
public static System.Drawing.Image GetThumbNailImage(System.Drawing.Image originalImage, int thumMaxWidth, int thumMaxHeight)
{
    Size thumRealSize = Size.Empty;
    System.Drawing.Image newImage = originalImage;
    Graphics graphics = null;
    try
    {
        thumRealSize = GetNewSize(thumMaxWidth, thumMaxHeight, originalImage.Width, originalImage.Height);
        newImage = new Bitmap(thumRealSize.Width, thumRealSize.Height);
        graphics = Graphics.FromImage(newImage);
        graphics.CompositingQuality = CompositingQuality.HighQuality;
        graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
        graphics.SmoothingMode = SmoothingMode.HighQuality;
        graphics.Clear(Color.Transparent);
        graphics.DrawImage(originalImage, new Rectangle(0, 0, thumRealSize.Width, thumRealSize.Height), new Rectangle(0, 0, originalImage.Width, originalImage.Height), GraphicsUnit.Pixel);
    }
    catch { }
    finally
    {
        if (graphics != null)
        {
            graphics.Dispose();
            graphics = null;
        }
    }
    return newImage;
}

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