浅谈图片上传之剪切

对于一个网站来说，图片显示都是有一定的宽高比的，而客户上传的图片大多未经过剪切，故上传以后对图片进行一定的剪切是非常必要的。

如此，我们应当剪一个类来完成这项工作。

 public class ImageHelper｛

///图片宽高比，默认1.333
 double _webWidth=1.333;

/// <summary>
///网站显示图片的 宽/高比
/// </summary>
public double WebWidth
{
get { return _webWidth; }
set {_webWidth = value; }
}
/// <summary>
/// 根据宽高比剪切图片，_webWidth
/// </summary>
/// <param name="img">需要剪切的图片</param>
/// <returns></returns>
public Bitmap CutImage(Bitmap img)
{

int width = img.Width;
int height = img.Height;
Rectangle section = new Rectangle();

//假如宽带高于高度图片
if (width >= height)
{
//根据网站宽高比例计算出宽度
section.Width = (int)(height * _webWidth);
//剪切宽大于原宽，取原宽
if (section.Width > width)
section.Width = width;
section.Height = height;
section.Y = 0;

//计算出开始截图的X定位，计算方式为(原宽-剪切宽/2)
section.X = (int)((width - section.Width) / 2);
}

///假如高度大于宽度的图片
if (width < height)
{
//根据宽高比计算出高度，为宽度/宽高比
section.Height = (int)(width / _webWidth);
//剪切宽大于原高，取原高
if (section.Height > height)
section.Height = height;

section.Width = width;
section.X = 0;

//计算出开始截图的Y定位，计算方式为(原高-剪切高/2)
section.Y = (int)((height - section.Height) / 2);
}

Bitmap pickedImage = new Bitmap(section.Width, section.Height);
Graphics pickedG = Graphics.FromImage(pickedImage);
//开始剪切并填充
pickedG.DrawImage(img, new Rectangle(0, 0, section.Width, section.Height), section,
GraphicsUnit.Pixel);
return pickedImage;

}

｝