如果你正在使用BitmapSource:

var resizedBitmap = new TransformedBitmap(
    bitmapSource,
    new ScaleTransform(scaleX, scaleY));

如果你想要更好的控制质量，首先运行这个:

RenderOptions.SetBitmapScalingMode(
    bitmapSource,
    BitmapScalingMode.HighQuality);

(默认为BitmapScalingMode。线性，相当于BitmapScalingMode.LowQuality。)

不知道这有什么困难，做你正在做的，使用重载Bitmap构造函数来创建一个重新大小的图像，你唯一缺少的是转换回image数据类型:

public static Image resizeImage(Image imgToResize, Size size)
{
    return (Image)(new Bitmap(imgToResize, size));
}

yourImage = resizeImage(yourImage, new Size(50,50));

在这个问题中，你会得到一些答案，包括我的:

public Image resizeImage(int newWidth, int newHeight, string stPhotoPath)
 {
     Image imgPhoto = Image.FromFile(stPhotoPath); 

     int sourceWidth = imgPhoto.Width;
     int sourceHeight = imgPhoto.Height;

     //Consider vertical pics
    if (sourceWidth < sourceHeight)
    {
        int buff = newWidth;

        newWidth = newHeight;
        newHeight = buff;
    }

    int sourceX = 0, sourceY = 0, destX = 0, destY = 0;
    float nPercent = 0, nPercentW = 0, nPercentH = 0;

    nPercentW = ((float)newWidth / (float)sourceWidth);
    nPercentH = ((float)newHeight / (float)sourceHeight);
    if (nPercentH < nPercentW)
    {
        nPercent = nPercentH;
        destX = System.Convert.ToInt16((newWidth -
                  (sourceWidth * nPercent)) / 2);
    }
    else
    {
        nPercent = nPercentW;
        destY = System.Convert.ToInt16((newHeight -
                  (sourceHeight * nPercent)) / 2);
    }

    int destWidth = (int)(sourceWidth * nPercent);
    int destHeight = (int)(sourceHeight * nPercent);


    Bitmap bmPhoto = new Bitmap(newWidth, newHeight,
                  PixelFormat.Format24bppRgb);

    bmPhoto.SetResolution(imgPhoto.HorizontalResolution,
                 imgPhoto.VerticalResolution);

    Graphics grPhoto = Graphics.FromImage(bmPhoto);
    grPhoto.Clear(Color.Black);
    grPhoto.InterpolationMode =
        System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

    grPhoto.DrawImage(imgPhoto,
        new Rectangle(destX, destY, destWidth, destHeight),
        new Rectangle(sourceX, sourceY, sourceWidth, sourceHeight),
        GraphicsUnit.Pixel);

    grPhoto.Dispose();
    imgPhoto.Dispose();
    return bmPhoto;
}

本遗嘱-

调整宽度和高度，不需要循环 不超过图像的原始尺寸

//////////////

private void ResizeImage(Image img, double maxWidth, double maxHeight)
{
    double resizeWidth = img.Source.Width;
    double resizeHeight = img.Source.Height;

    double aspect = resizeWidth / resizeHeight;

    if (resizeWidth > maxWidth)
    {
        resizeWidth = maxWidth;
        resizeHeight = resizeWidth / aspect;
    }
    if (resizeHeight > maxHeight)
    {
        aspect = resizeWidth / resizeHeight;
        resizeHeight = maxHeight;
        resizeWidth = resizeHeight * aspect;
    }

    img.Width = resizeWidth;
    img.Height = resizeHeight;
}

下面的函数将返回显示图像的新大小。这在这里可能没有帮助。但它将返回调整大小的显示矩形大小。

 public static  class ResizeImage
{
    /// <summary>
    /// Return new resized size to display the image
    /// </summary>
    /// <param name="srcrectanle">source rectangle of image or you can pass the bitmap and set the size accrodingly</param>
    /// <param name="initSize">initial size of the page to draw image</param>
    /// <returns></returns>
    public static SizeF getResizedRectangle(RectangleF srcrectanle, SizeF initSize)
    {
        float sw = srcrectanle.Width;
        float sh = srcrectanle.Height;
        float dw = initSize.Width;
        float dh = initSize.Height;
        float finalHeight, finalWidth;
        float Sourceratio = sw / sh;

        if (Sourceratio >= 1)
        {
            finalWidth = (int)dw;
            float ratio = sw / dw;
            finalHeight = (sh / ratio);
        }
        else
        {
            finalHeight = (int)dh;
            float ratio = sh / dh;
            finalWidth = (sw / ratio);
        }
        return new SizeF(finalHeight, finalHeight);


    }
}

为什么不用System.Drawing.Image.GetThumbnailImage方法呢?

public Image GetThumbnailImage(
    int thumbWidth, 
    int thumbHeight, 
    Image.GetThumbnailImageAbort callback, 
    IntPtr callbackData)

例子:

Image originalImage = System.Drawing.Image.FromStream(inputStream, true, true);
Image resizedImage = originalImage.GetThumbnailImage(newWidth, (newWidth * originalImage.Height) / originalWidth, null, IntPtr.Zero);
resizedImage.Save(imagePath, ImageFormat.Png);

来源: http://msdn.microsoft.com/en-us/library/system.drawing.image.getthumbnailimage.aspx