网站中集成jquery.imgareaselect实现图片的本地预览和选择截取

<img id="ferret" src="" alt="It‘s coming right for us!" title="It‘s coming right for us!"
        style="float: left; margin-right: 10px; width: 400px; height: 300px" />
    
    <input type="hidden" name="x1" value="" />
    <input type="hidden" name="y1" value="" />
    <input type="hidden" name="x2" value="" />
    <input type="hidden" name="y2" value="" />
    <input id="loadFile" type="file" name="name" onchange="readURL(this);" />
    <input type="submit" name="submit" value="Submit" />

<script type="text/javascript">
        //绘制小图
        function preview(img, selection) {
            var scaleX = 100 / (selection.width || 1);
            var scaleY = 100 / (selection.height || 1);

            $(‘#ferret + div > img‘).css({
                width: Math.round(scaleX * 400) + ‘px‘,
                height: Math.round(scaleY * 300) + ‘px‘,
                marginLeft: ‘-‘ + Math.round(scaleX * selection.x1) + ‘px‘,
                marginTop: ‘-‘ + Math.round(scaleY * selection.y1) + ‘px‘
            });
        }

        $(document).ready(function () {
            //添加小图
            $(‘<div><img id="ferret1"  src="" style="position: relative;" /><div>‘)
        .css({
            float: ‘left‘,
            position: ‘relative‘,
            overflow: ‘hidden‘,
            width: ‘100px‘,
            height: ‘100px‘
        })
        .insertAfter($(‘#ferret‘));
            //主图编辑
            $(‘#ferret‘).imgAreaSelect({ x1: 120, y1: 90, x2: 280, y2: 210, aspectRatio: ‘4:3‘, onSelectChange: preview, onSelectEnd: function (img, selection) {
                $(‘input[name="x1"]‘).val(selection.x1);
                $(‘input[name="y1"]‘).val(selection.y1);
                $(‘input[name="x2"]‘).val(selection.x2);
                $(‘input[name="y2"]‘).val(selection.y2);
            }
            });
        });


        //本地预览
        function readURL(input) {
            var strSrc = $("#loadFile").val();

            //验证上传文件格式是否正确  
            var pos = strSrc.lastIndexOf(".");
            var lastname = strSrc.substring(pos, strSrc.length);
            if (lastname.toLowerCase() != ".jpg") {
                alert("您上传的文件类型为" + lastname + "，图片必须为 JPG 类型");
                return false;
            }

            //验证上传文件是否超出了大小  
            if (input.files[0].size / 1024 > 150) {
                alert("您上传的文件大小超出了150K限制！");
                return false;
            }


            if (input.files && input.files[0]) {
                var reader = new FileReader();


                reader.onload = function (e) {
                    $(‘#ferret‘).attr(‘src‘, e.target.result);
                    $(‘#ferret1‘).attr(‘src‘, e.target.result);
                };

                reader.readAsDataURL(input.files[0]);
            }
        }
    </script>

protected void Page_Load(object sender, EventArgs e)
        {
            if (IsPostBack)
            {
                int x1 = Convert.ToInt32(Request["x1"]);
                int y1 = Convert.ToInt32(Request["y1"]);
                int x2 = Convert.ToInt32(Request["x2"]);
                int y2 = Convert.ToInt32(Request["y2"]);


                HttpFileCollection files = Request.Files;
                for (int i = 0; i < files.Count; i++)
                {
                    HttpPostedFile file = files[i];
                    file.SaveAs(Server.MapPath("Upload/" + file.FileName));

                    //设置缩略图
                    int Thumbnailwidth = 400;
                    int Thumbnailheight = 300;
                    //新建一个bmp图片  
                    Bitmap bitmap = new Bitmap(Thumbnailwidth, Thumbnailheight);

                    //新建一个画板  
                    Graphics graphic = Graphics.FromImage(bitmap);

                    //设置高质量插值法  
                    graphic.InterpolationMode = InterpolationMode.High;

                    //设置高质量,低速度呈现平滑程度  
                    graphic.SmoothingMode = SmoothingMode.HighQuality;

                    //清空画布并以透明背景色填充  
                    graphic.Clear(System.Drawing.Color.Transparent);

                    //原图片
                    Bitmap originalImage = new Bitmap(file.InputStream);

                    //在指定位置并且按指定大小绘制原图片的指定部分  
                    graphic.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, Thumbnailwidth, Thumbnailheight),
                        new System.Drawing.Rectangle(0, 0, originalImage.Width, originalImage.Height),
                        System.Drawing.GraphicsUnit.Pixel);

                    //得到缩略图
                    System.Drawing.Image ThumbnailImage = System.Drawing.Image.FromHbitmap(bitmap.GetHbitmap());

                    //创建选择图片
                    Bitmap selectbitmap = new Bitmap(x2-x1, y2-y1);

                    //新建一个画板  
                    Graphics selectgraphic = Graphics.FromImage(selectbitmap);
                   

                    //裁切
                    selectgraphic.DrawImage(ThumbnailImage, 0, 0, new Rectangle(x1, y1, x2 - x1, y2 - y1), GraphicsUnit.Pixel);

                    //保存
                    selectbitmap.Save(Server.MapPath("Upload/"+Guid.NewGuid() + file.FileName), ImageFormat.Jpeg);

                   //todo:将上述资源释放

                }
            }
        }