如何在保持正確的寬高比的同時保存縮略圖？

Question

我正在使用ASP.net開發一個網站。 用戶可以在那里上傳圖像。 保存圖像時，我正在保存一個小版本（Thumbnail）圖像。 為此，我使用此代碼

public void SaveThumbnailImage(Stream sourcePath, int width, int height, string imageFileName)
{
    using (var image = System.Drawing.Image.FromStream(sourcePath))
    {
        //a holder for the result
        Bitmap result = new Bitmap(width, height);

        //set the resolutions the same to avoid cropping due to resolution differences
        result.SetResolution(image.HorizontalResolution, image.VerticalResolution);

        //use a graphics object to draw the resized image into the bitmap
        using (Graphics graphics = Graphics.FromImage(result))
        {
            //set the resize quality modes to high quality
            graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
            graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
            //draw the image into the target bitmap
            graphics.DrawImage(image, 0, 0, result.Width, result.Height);
        }

        thumbnailfullImagePath = string.Format("/Images/thumbnail/{0}", imageFileName);
        result.Save(Server.MapPath(thumbnailfullImagePath), image.RawFormat);
    }
}

高度是：105寬度是150

上面的線可以很好地用於風景照片。 但是，如果我上傳人像照片，將無法保持其正確的還原效果。 那么，如何優化上述代碼以保存縮略圖，同時保持其原始寬高比呢？

Answer 1

您可以通過某種方式簡單地減少圖像的寬度和高度。 這是我使用系數10的示例代碼。

using System;
using System.Drawing;

public partial class thumbnail : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
       System.Drawing.Image image = System.Drawing.Image.FromFile(Server.MapPath("images/send.png"));

        int factor = 10;
        int new_width = image.Width / factor;
        int new_height = image.Height / factor;

        System.Drawing.Image thumbnail = image.GetThumbnailImage(new_width,
            new_height, null, IntPtr.Zero);

        thumbnail.Save(Server.MapPath("images/send_thumbnail.png"));
    }
}