从 C# 中的字节数组中删除 0 值

Question

我有这个代码：

[WebMethod]
public static string SaveImg(string imgdata)
{

    string Path = "UploadedImages/";
    string folderPath = HttpContext.Current.Server.MapPath(Path);
    Guid gid=Guid.NewGuid();
    string fileNameWitPath = folderPath + "img_" +gid  + ".png";

    FileStream fs = new FileStream(fileNameWitPath, FileMode.Create);
    BinaryWriter bw = new BinaryWriter(fs);

    byte[] data = Convert.FromBase64String(imgdata);

    bw.Write(data);
    bw.Close();
    bw.Dispose();
    return  "/" + Path +"img_"+ gid + ".png";
}

witch 是一个函数，它接受一个 base64 字符串并将其转换为二进制并将图像保存到服务器

base64 数据取自在上传时加载图像的画布 图像看起来像这样：

除非您在新选项卡中打开示例图像，否则我的问题不会显示，您可以看到它周围包含白色边框，因为当它被上传到画布时它不适合画布大小

我的问题是如何在将图像保存到服务器（bw.write(data)）之前从图像中删除那些白色边框（从字节数组中删除0 byte） 我试过这段代码，但它对我不起作用：

int i = data.Length - 1;
while(data[i] == 0)
   --i;
// now data[i] is the last non-zero byte
byte[] bar = new byte[i+1];
Array.Copy(data, bar, i+1);
bw.Write(data);

这是客户端代码：

        var canvas = $("#imageCanvas")[0];
        var ctx = canvas.getContext("2d");
        var uploadInput = $('#UploadFile');
        var width = 382;
        var height = 295;
uploadInput.on('change', function (e) {
            RemoveDisabledClass();
            handleImage(e);
        });

        function handleImage(e) {
            var reader = new FileReader();
            reader.onload = function (event) {
                var img = new Image();
                img.onload = function () {
                    // var canvas = ctx.canvas;
                    var hRatio = canvas.width / img.width;
                    var vRatio = canvas.height / img.height;
                    var ratio = Math.min(hRatio, vRatio);
                    var centerShift_x = (canvas.width - img.width * ratio) / 2;
                    var centerShift_y = (canvas.height - img.height * ratio) / 2;
                    ctx.clearRect(0, 0, canvas.width, canvas.height);
                    ctx.drawImage(img, 0, 0, img.width, img.height,
                                       centerShift_x, centerShift_y, img.width * ratio, img.height * ratio);
                }
                img.src = event.target.result;

            }
            reader.readAsDataURL(e.target.files[0]);
        }

        $("#btn_save").click(function () {
            if ($("#btn_save").hasClass("disabled")) return;
            $("#dv_Error").css("display", "none");
            var image = document.getElementById("imageCanvas").toDataURL();
            image = image.replace('data:image/png;base64,', '');
            $.ajax({
                type: 'POST',
                url: 'Default.aspx/SaveImg',
                data: '{ "imgdata" : "' + image + '" }',
                contentType: 'application/json; charset=utf-8',
                dataType: 'json',
                success: function (data) {
                    window.location.href = data.d;

                },
                error: function (request, status, error) {
                    $("#dv_Error").css("display", "block");

                }

            }); //ENd Ajax
        }); //End Click event

Answer 1

如果您想简单地从字节数组中删除 0，您可以不使用 LINQ 吗？通过导入命名空间，您可以使用此代码检查数组中的所有 0 值并选择不为 0 的值并将其重写到数组：

data = data.Where(x => x != 0).ToArray();

希望对你有所帮助。

问候， 沃伦

Answer 2

一种解决方案是使用 ImageProcessor (https://github.com/JimBobSquarePants/ImageProcessor) 之类的东西 - 它包含一个处理器，可以完全满足您的需求：

   // Read a file and resize it.
   byte[] source = File.ReadAllBytes(file);

   using (MemoryStream inStream = new MemoryStream(source))
       using (MemoryStream outStream = new MemoryStream())
           using (ImageFactory imageFactory = new ImageFactory())
           {
               // Load, remove whitespace around image and save an image.
               imageFactory.Load(inStream)
                    .EntropyCrop()
                    .Save(outStream);

            } 
        }
    }

EntropyCrop 处理器会将图像裁剪到熵最大的区域。换句话说，它将删除图像周围的空白。

ImageProcessor.Web 项目中还有一个基于 url 的 web api。

代码参考：

• https://github.com/JimBobSquarePants/ImageProcessor/blob/V2/src/ImageProcessor/ImageFactory.cs#L648-L666
• https://github.com/JimBobSquarePants/ImageProcessor/blob/V2/src/ImageProcessor/Processors/EntropyCrop.cs
• https://github.com/JimBobSquarePants/ImageProcessor/wiki/ImageProcessor