C#.NET：调整容器div元素内图像的大小

我有以下标记代码，其中包含container div元素和嵌套在div中的img标记。container div具有width、height、top和left CSS样式属性

最初上传的图像具有任意宽度和高度，可能大于或小于容器分区。因此，必须调整最初上传的图像的大小并进行良好缩放，并将其保存为缩略图，以位于容器分区的边界内。调整大小的缩略图将显示为源（src）在以下标记中：

<div id="divContainer" style="width: 600px; height: 450px; top: 50px; left: 20px;">
   <img src="[my resized and well scaled thumbnail source]..." id="imgResizedThumnail" />
</div>

这就是我使用的：

    public static Image Resize(
        Image srcImage, 
        int newWidth, 
        int maxHeight,
        int dpi = 72)
    {
        if(srcImage.Width<=newWidth)
        {
            newWidth = srcImage.Width;
        }

        var newHeight = srcImage.Height * newWidth / srcImage.Width;
        if (newHeight > maxHeight)
        {
            newWidth = srcImage.Width * maxHeight / srcImage.Height;
            newHeight = maxHeight;
        }

        var newImage = new Bitmap(newWidth, newHeight);
        newImage.SetResolution(dpi, dpi);

        using (var gr = Graphics.FromImage(newImage))
        {
            gr.SmoothingMode = SmoothingMode.AntiAlias;
            gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
            gr.PixelOffsetMode = PixelOffsetMode.HighQuality;
            gr.DrawImage(srcImage, new Rectangle(0, 0, newWidth, newHeight));
        }
        return newImage;
    }

公共静态图像大小调整(
图像，图像，
int newWidth，
int最大高度，
int dpi=72）
{
if（srcImage.Width maxHeight）
{
newWidth=srcImage.Width*maxHeight/srcImage.Height；
newHeight=maxHeight；
}
var newImage=新位图（新宽度、新高度）；
设置分辨率（dpi，dpi）；
使用（var gr=Graphics.FromImage（newImage））
{
gr.SmoothingMode=SmoothingMode.AntiAlias；
gr.InterpolationMode=InterpolationMode.HighQualityBicubic；
gr.PixelOffsetMode=PixelOffsetMode.HighQuality；
gr.DrawImage（srcImage，新矩形（0，0，newWidth，newHeight））；
}
返回新图像；
}

我会这样做：

public void SaveThumbnailImageWithbestScaling(Image originalImage, int containerDivWidth, int containerDivHeight)
{
    string thumbnailFilename = "myThumnailFileName";
    int thumbnailWidth = 0;
    int thumbnailHeight = 0;

    float imgWidth = (float)originalImage.Width;
    float imgHeight = (float)originalImage.Height;

    float scale_w = imgWidth / (float)containerDivWidth;
    float scale_h = imgHeight / (float)containerDivHeight;

    // Compute how much each scale diverge from 1 (1 means no scaling, which is desirable)
    float variance_w = Math.Abs(1.0 - scale_w);
    float variance_h = Math.Abs(1.0 - scale_h);

    if (variance_w > variance_h)
    {
        // Height ratio is closer to 1
        float aspect_ratio = imgWidth / imgHeight;
        thumbnailHeight = containerDivHeight;
        thumbnailWidth = (int)Math.Floor(aspect_ratio * imgWidth);
    }
    else
    {
        // Width ratio is closer to 1
        float aspect_ratio = imgHeight / imgWidth;
        thumbnailHeight = (int)Math.Floor(aspect_ratio * imgHeight);
        thumbnailWidth = containerDivWidth;
    }

    Bitmap thumnailImage = CreateThumbnail(thumbnailFilename,int thumnailWidth, int thumnailHeight);

    // 3. save thumbnail
    SaveThumnail(thumnailImage);   
}

该算法计算每个维度的比率，然后找出哪个维度与div标记的维度差异最大。然后，它继续捕捉与div标记大小差异最小的维度，并缩放另一个维度以考虑图像的纵横比

当然还有其他方法，例如，您可以不关心纵横比，只将两个维度捕捉到div标记的维度

public void SaveThumbnailImageWithbestScaling(Image originalImage, int containerDivWidth, int containerDivHeight)
{
    string thumbnailFilename = "myThumnailFileName";
    int thumbnailWidth = 0;
    int thumbnailHeight = 0;

    float imgWidth = (float)originalImage.Width;
    float imgHeight = (float)originalImage.Height;

    float scale_w = imgWidth / (float)containerDivWidth;
    float scale_h = imgHeight / (float)containerDivHeight;

    // Compute how much each scale diverge from 1 (1 means no scaling, which is desirable)
    float variance_w = Math.Abs(1.0 - scale_w);
    float variance_h = Math.Abs(1.0 - scale_h);

    if (variance_w > variance_h)
    {
        // Height ratio is closer to 1
        float aspect_ratio = imgWidth / imgHeight;
        thumbnailHeight = containerDivHeight;
        thumbnailWidth = (int)Math.Floor(aspect_ratio * imgWidth);
    }
    else
    {
        // Width ratio is closer to 1
        float aspect_ratio = imgHeight / imgWidth;
        thumbnailHeight = (int)Math.Floor(aspect_ratio * imgHeight);
        thumbnailWidth = containerDivWidth;
    }

    Bitmap thumnailImage = CreateThumbnail(thumbnailFilename,int thumnailWidth, int thumnailHeight);

    // 3. save thumbnail
    SaveThumnail(thumnailImage);   
}