怎么对图片裁剪

我现在想做了个图片裁剪，比如原图片h =500px  w= 500px ，但需要裁图中的 h =200px  w= 100px 部分怎么处理呢 --------------------编程问答-------------------- 即就是上传图片后进行局部的图像裁剪，并保存为文件这种功能 --------------------编程问答-------------------- 等比例缩放图片
<script language="JavaScript">
var flag=false;
function DrawImage(ImgD,iwidth,iheight){
    var image=new Image();
    image.src=ImgD.src;
    if(image.width>0 && image.height>0){
    flag=true;
    if(image.width/image.height>= iwidth/iheight){
        if(image.width>iwidth){
        ImgD.width=iwidth;
        ImgD.height=(image.height*iwidth)/image.width;
        }else{
        ImgD.width=image.width;
        ImgD.height=image.height;
        }
        ImgD.alt=image.width+"×"+image.height;
        }
    else{
        if(image.height>iheight){
        ImgD.height=iheight;
        ImgD.width=(image.width*iheight)/image.height;
        }else{
        ImgD.width=image.width;
        ImgD.height=image.height;
        }
        ImgD.alt=image.width+"×"+image.height;
        }

    }
}
onload="javascript:DrawImage1(this)">
上传图片生成缩略图
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
{
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
int towidth = width;
int toheight = height;
int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;
switch (mode)
{
case "HW":
break;
case "W":
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H":
towidth = originalImage.Width * height / originalImage.Height;
break;
case "Cut":
if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = (originalImage.Width - ow) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = (originalImage.Height - oh) / 2;
}
break;
default:
break;
}
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
g.Clear(System.Drawing.Color.Transparent);
g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),
new System.Drawing.Rectangle(x, y, ow, oh),
System.Drawing.GraphicsUnit.Pixel);

try
{
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}
--------------------编程问答-------------------- 跟着如梦走，知识天天有

--------------------编程问答--------------------

using System.Drawing;

using System.Drawing.Drawing2D;



protected void Page_Load(object sender, EventArgs e)

{

    System.Drawing.Image img = Test("C:\\1.jpg", 0, 0, 200, 100);

    img.Save("C:\\2.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

    img.Dispose();

}

public System.Drawing.Image Test(string imgPath, int x, int y, int width, int height)

{

    System.Drawing.Image xImg = System.Drawing.Image.FromFile(imgPath);

    System.Drawing.Image oImg = new Bitmap(width, height, xImg.PixelFormat);

    Graphics g = Graphics.FromImage(oImg);

    g.CompositingQuality = CompositingQuality.HighSpeed;

    g.SmoothingMode = SmoothingMode.HighSpeed;

    g.InterpolationMode = InterpolationMode.HighQualityBilinear;



    g.DrawImage(xImg, new Rectangle(0, 0, width, height), new Rectangle(x, y, width, height), GraphicsUnit.Pixel);

    xImg.Dispose();



    return oImg;

}

--------------------编程问答-------------------- 楼上都贴了我就不贴了，呵呵 --------------------编程问答-------------------- 不错
每天回帖即可获得10分可用分！小技巧：教您如何更快获得可用分 --------------------编程问答--------------------

 /// <summary>

        /// 裁剪

        /// </summary>

        /// <param name="xPosition">X起始点</param>

        /// <param name="yPosition">Y起始点</param>

        /// <param name="width">宽</param>

        /// <param name="height">高</param>

        public void DrawOutCropArea(int xPosition, int yPosition, int width, int height)

        {

            _bitmapPrevCropArea = (Bitmap)_currentBitmap;

            Bitmap bmap = (Bitmap)_bitmapPrevCropArea.Clone();

            Graphics gr = Graphics.FromImage(bmap);

            Brush cBrush = new Pen(Color.FromArgb(150, Color.White)).Brush;

            Rectangle rect1 = new Rectangle(0, 0, _currentBitmap.Width, yPosition);

            Rectangle rect2 = new Rectangle(0, yPosition, xPosition, height);

            Rectangle rect3 = new Rectangle(0, (yPosition + height), _currentBitmap.Width, _currentBitmap.Height);

            Rectangle rect4 = new Rectangle((xPosition + width), yPosition, (_currentBitmap.Width - xPosition - width), height);

            gr.FillRectangle(cBrush, rect1);

            gr.FillRectangle(cBrush, rect2);

            gr.FillRectangle(cBrush, rect3);

            gr.FillRectangle(cBrush, rect4);

            _currentBitmap = (Bitmap)bmap.Clone();

        }

--------------------编程问答-------------------- UploadAndCrop 图片裁剪 http://www.cnblogs.com/zengxiangzhan/archive/2009/12/27/1633644.html
图片裁剪 PhotoCropper
http://www.cnblogs.com/zengxiangzhan/archive/2010/01/04/1638780.html --------------------编程问答--------------------

引用 8 楼 zengzhan 的回复:

UploadAndCrop 图片裁剪 http://www.cnblogs.com/zengxiangzhan/archive/2009/12/27/1633644.html
图片裁剪 PhotoCropper
http://www.cnblogs.com/zengxiangzhan/archive/2010/01/04/1638780.html

谢谢我马上测试一下 --------------------编程问答-------------------- 我想,问一下,怎么给要打水印文字换行.
谢谢!

补充：.NET技术 ,  ASP.NET