我想使用 asp.net 将多个 Canvas 保存到一个图像中。我尝试使用两张 Canvas ，但没有保存。

Canvas :

    <div style="position:relative; width:456px; padding:0px; margin:0px;">
    <canvas id="boardcanvas" width="456" height="480" style="position: absolute; left: 0;   top: -220px; z-index: 0;"></canvas>
    <canvas id="layer2" width="456" height="480" style="position: absolute;left: 0;   top:-220px; z-index: 1;"></canvas>    
   </div>


 <input type="button" id="btnSave" style="width:150px ; text-align:center;height:30px" name="btnSave" value="Save as Image!" />

J查询:

<script type="text/javascript">
     // Send the canvas image to the server.
     $(function () {
         $("#btnSave").click(function () {

             can1 = document.getElementById("broadcanvas");
             ctx1 = can1.getContext("2d");
             var coll = document.getElementById("layer2");
             ctx1.drawImage(coll, 0, 0);
             var image = can1.toDataURL("image/png");   

             alert(image);
             image = image.replace('data:image/png;base64,', '');
             $.ajax({
                 type: 'POST',
                 url: 'index.aspx/UploadImage',
                 data: '{ "imageData" : "' + image + '" }',
                 contentType: 'application/json; charset=utf-8',
                 dataType: 'json',
                 success: function (msg) {
                     alert('Image saved successfully !');
                 }
             });
         });
     });
</script>

index.aspx.cs:

using System.IO;
using System.Web.Script.Services;
using System.Web.Services;

[ScriptService]
public partial class index : System.Web.UI.Page
{
    static string path = @"E:\Green\images\\";
    protected void Page_Load(object sender, EventArgs e)
    {


    }
    [WebMethod()]
    public static void UploadImage(string imageData)
    {
       string fileNameWitPath = path + DateTime.Now.ToString().Replace("/", "-").Replace(" ", "- ").Replace(":", "") + ".png";
       using (FileStream fs = new FileStream(fileNameWitPath, FileMode.Create))
        {
           using (BinaryWriter bw = new BinaryWriter(fs))
             {
                byte[] data = Convert.FromBase64String(imageData);
                bw.Write(data);
                bw.Close();
             }
         }
     }
}

最佳答案

为了这段代码的正常工作，你必须做下面的事情

1. 更正 javascript 代码中使用的 Canvas ID 的拼写。
2. 改变按钮的位置。当前按钮在 Canvas 下。所以不能点击按钮。
3. 在 E 盘创建目录 Green 和 Images。它应该在那里 E:\Green\Images

工作代码是。

Javascript

<script type="text/javascript">
        // Send the canvas image to the server.
        $(function () {
            $("#btnSave").click(function () {
                can1 = document.getElementById("boardcanvas");
                ctx1 = can1.getContext("2d");
                var coll = document.getElementById("layer2");
                ctx1.drawImage(coll, 0, 0);
                var image = can1.toDataURL("image/png");

                alert(image);
                image = image.replace('data:image/png;base64,', '');
                $.ajax({
                    type: 'POST',
                    url: 'Default.aspx/UploadImage',
                    data: '{ "imageData" : "' + image + '" }',
                    contentType: 'application/json; charset=utf-8',
                    dataType: 'json',
                    success: function (msg) {
                        alert('Image saved successfully !');
                    }
                });
            });
        });
    </script>

HTML代码

<div style="position: relative; width: 456px; padding: 0px; margin: 0px;">
        <canvas id="boardcanvas" width="456" height="480" style="position: absolute; left: 0;
            top: -220px; z-index: 0;">
        </canvas>
        <canvas id="layer2" width="456" height="480" style="position: absolute; left: 0;
            top: -220px; z-index: 1;">
        </canvas>
    </div>
    <input type="button" id="btnSave" style="position: absolute; left: 460px; width: 150px;
        text-align: center; height: 30px; z-index: 2;" name="btnSave" value="Save as Image!" />

Asp.Net 端代码没问题。 请尝试使用上面的代码。当然可以(不要忘记创建目录)。

关于javascript - 如何将多个 Canvas 保存到一个图像中，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12419141/