c# - ASP.Net MVC 图像上传通过缩小或填充调整大小

Question

用户将能够上传图片。如果图像大于设定尺寸，我想将其缩小到该尺寸。显然，由于比率，它不必完全匹配，宽度将是关键大小，因此高度将是可变的。

如果图像小于设置的尺寸，我想创建一个新图像，使其达到设置的尺寸，背景为定义的颜色，然后将上传的图像居中放置，因此结果是带有填充颜色的原始图像。

非常感谢任何代码示例或链接

Answer 1

这是我快速编写的一段代码，用于根据宽度调整它的大小。我相信您能弄清楚如何向位图添加背景颜色。它不是完整的代码，而只是关于如何做事的想法。

public static void ResizeLogo(string originalFilename, string resizeFilename)
{
    Image imgOriginal = Image.FromFile(originalFilename);

    //pass in whatever value you want for the width (180)
    Image imgActual = ScaleBySize(imgOriginal, 180);
    imgActual.Save(resizeFilename);
    imgActual.Dispose();
}

public static Image ScaleBySize(Image imgPhoto, int size)
{
    int logoSize = size;

    float sourceWidth = imgPhoto.Width;
    float sourceHeight = imgPhoto.Height;
    float destHeight = 0;
    float destWidth = 0;
    int sourceX = 0;
    int sourceY = 0;
    int destX = 0;
    int destY = 0;

    // Resize Image to have the height = logoSize/2 or width = logoSize.
    // Height is greater than width, set Height = logoSize and resize width accordingly
    if (sourceWidth > (2 * sourceHeight))
    {
        destWidth = logoSize;
        destHeight = (float)(sourceHeight * logoSize / sourceWidth);
    }
    else
    {
        int h = logoSize / 2;
        destHeight = h;
        destWidth = (float)(sourceWidth * h / sourceHeight);
    }
    // Width is greater than height, set Width = logoSize and resize height accordingly

    Bitmap bmPhoto = new Bitmap((int)destWidth, (int)destHeight, 
                                PixelFormat.Format32bppPArgb);
    bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

    Graphics grPhoto = Graphics.FromImage(bmPhoto);
    grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;

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

    grPhoto.Dispose();

    return bmPhoto;
}