Question

我正在尝试下载大约1000张图片。为此，我首先生成随机数，将此文本转换为图像。在按钮单击后，我正在下载此生成的图像。这工作正常。现在我想运行这个循环1000次，这样我就可以下载数千张图像。当循环运行一次时，下面的代码工作正常，但是当循环运行1000次时，它不能正常工作。

另外，我想更改应下载此图像的目标文件夹。我怎样才能做到这一点？



Below if I change value of variable i to 1000, the output is not what I am expecting

public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            for (int i = 0; i < 1; i++)
            {
                CallBUttonClick();
            }

    }


    protected void Button1_Click(object sender, EventArgs e)
    {
        var s = GenerateRandomCode();
        RandomImage ci = new RandomImage(s.ToString(), 300, 75);
        this.Response.Clear();
        this.Response.ContentType = "image/jpeg";
        Response.AppendHeader("Content-Disposition", "attachment; filename=downloadedFile.JPG");
        ci.Image.Save(this.Response.OutputStream, ImageFormat.Jpeg);
        ci.Dispose();

    }

    protected void CallBUttonClick()
    {
        Button1_Click(Button1, null);
    }

    private string GenerateRandomCode()
    {
        Random r = new Random();
        string s = "";
        for (int j = 0; j < 5; j++)
        {
            int i = r.Next(3);
            int ch;
            switch (i)
            {
                case 1:
                    ch = r.Next(0, 9);
                    s = s + ch.ToString();
                    break;
                case 2:
                    ch = r.Next(65, 90);
                    s = s + Convert.ToChar(ch).ToString();
                    break;
                case 3:
                    ch = r.Next(97, 122);
                    s = s + Convert.ToChar(ch).ToString();
                    break;
                default:
                    ch = r.Next(97, 122);
                    s = s + Convert.ToChar(ch).ToString();
                    break;
            }
            r.NextDouble();
            r.Next(100, 1999);
        }
        return s;
    }
}


Adding RandomImage.cs class file
   

using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Drawing.Text;
using System;
public class RandomImage
{
    //Default Constructor 
    public RandomImage() { }
    //property
    public string Text
    {
        get { return this.text; }
    }
    public Bitmap Image
    {
        get { return this.image; }
    }
    public int Width
    {
        get { return this.width; }
    }
    public int Height
    {
        get { return this.height; }
    }
    //Private variable
    private string text;
    private int width;
    private int height;
    private Bitmap image;
    private Random random = new Random();
    //Methods declaration
    public RandomImage(string s, int width, int height)
    {
        this.text = s;
        this.SetDimensions(width, height);
        this.GenerateImage();
    }
    public void Dispose()
    {
        GC.SuppressFinalize(this);
        this.Dispose(true);
    }
    protected virtual void Dispose(bool disposing)
    {
        if (disposing)
            this.image.Dispose();
    }
    private void SetDimensions(int width, int height)
    {
        if (width <= 0)
            throw new ArgumentOutOfRangeException("width", width,
                "Argument out of range, must be greater than zero.");
        if (height <= 0)
            throw new ArgumentOutOfRangeException("height", height,
                "Argument out of range, must be greater than zero.");
        this.width = width;
        this.height = height;
    }
    private void GenerateImage()
    {
        Bitmap bmp = new Bitmap(1, 1);

        Graphics graphics = Graphics.FromImage(bmp);
        Font font = new Font(FontFamily.GenericSansSerif, 28);
        SizeF stringSize = graphics.MeasureString(this.text, font);
        bmp = new Bitmap(bmp, (int)stringSize.Width+30, (int)stringSize.Height+30);
        graphics = Graphics.FromImage(bmp);
        graphics.DrawString(this.text, font, Brushes.White, 0, 0);
        font.Dispose();
        graphics.Flush();
        graphics.Dispose();
        this.image = bmp;

    }
}

Answer 1

您好需要在physcial文件夹中保存位图文件。我修改了你的代码。请参阅以下代码

private void GenerateImage()
    {
        Bitmap bmp = new Bitmap(1, 1);

        Graphics graphics = Graphics.FromImage(bmp);
        Font font = new Font(FontFamily.GenericSansSerif, 28);
        SizeF stringSize = graphics.MeasureString(this.text, font);
        bmp = new Bitmap(bmp, (int)stringSize.Width + 30, (int)stringSize.Height + 30);
        graphics = Graphics.FromImage(bmp);
        graphics.DrawString(this.text, font, Brushes.White, 0, 0);
        font.Dispose();
        graphics.Flush();
        graphics.Dispose();
        bmp.Save("C:\\" + this.text + ".jpg");
        this.image = bmp;


    }

我还从按钮点击中移除了以下代码并休息，它工作正常。

//this.Response.Clear();
        //this.Response.ContentType = "image/jpeg";
        //Response.AppendHeader("Content-Disposition", "attachment; filename=downloadedFile.JPG");

        //ci.Image.Save(this.Response.OutputStream, ImageFormat.Jpeg);
        //ci.Dispose();

Answer 2

这不是ASP.NET Page Life Cycle的工作方式。如果使用Response对象提供下载，则可以提供ONE文件。

你正在从错误的方面解决问题;你说“我想下载大约1000张图片”。如果您愿意，这是客户端的一个过程，在浏览器上。

然而，您正试图在服务器端解决此问题。

您需要1000次下载，因此您必须从客户端启动1000次下载，并让服务器端（您正在为此编写的那一页）直播1000次。

换句话说，你不能从服务器“推送下载”多个文件，你必须逐个请求它们。

自动多次下载生成的图像

2 个答案: