如何改变图片的真实大小，而不是在屏幕上暂时缩放？

[dvdvip]

我知道，能直接设置PictureBox的SizeMode属性为Zoom后。再设置PictureBox的Width和Height.
例如：

private void Button1_Click(object sender,EventArgs e)
 {this.PictureBox1.Width=this.PictureBox1.Width*4;
  this.PictureBox1.Height=this.PictureBox1.Height*4;}

这样，图片在屏幕上就被拉伸为原来的4倍。
但是，图片实际大小实现上没有改变。它只不过是在屏幕上被暂时放大。

 private void Button2_Click(object sender,EventArgs e)
 {string wh=this.PictureBox1.Image.Width.ToString()+@"  "+this.PictureBox1.Image.Height.ToString();MessageBox.Show(wh);}

这个可以看出来，图片没有被真正地改变大小。这个PictureBox好像在骗人的。不能帮我直接改变图片的真实大小。

我以后还要直接对图片处理里。例如：

 Bitmap kk=new Bitmap(原图片变成4倍后的新图片);

请问C#有什么办法，可以生成一个新的图片kk, 它的真实大小是原来的4倍？

[路人乙e]

        ///  <summary> 
        /// 生成缩略图 
        ///  </summary> 
        ///  <param name="originalImagePath">源图路径（物理路径）</param> 
        ///  <param name="fileStream">文件流（与原路径二者选一）</param> 
        ///  <param name="thumbnailPath">缩略图路径（物理路径）</param> 
        ///  <param name="width">缩略图宽度</param> 
        ///  <param name="height">缩略图高度</param> 
        ///  <param name="mode">生成缩略图的方式(HW,W,H,Cut)</param>
        public static void MakeThumbnail(string originalImagePath, Stream fileStream, string thumbnailPath, int width, int height, string mode)
        {
            Image originalImage = null;
            if (originalImagePath != "") originalImage = Image.FromFile(originalImagePath);
            else originalImage = Image.FromStream(fileStream);

            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;

            switch (mode)
            {
                case "HW"://指定高宽缩放（可能变形）                 
                    break;
                case "W"://指定宽，高按比例
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
                case "H"://指定高，宽按比例 
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case "Cut"://指定高宽裁减（不变形）                 
                    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:
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
            }

            
            Image bitmap = new Bitmap(towidth, toheight);//新建一个bmp图片 

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

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

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

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

            //在指定位置并且按指定大小绘制原图片的指定部分 
            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), new Rectangle(x, y, ow, oh), GraphicsUnit.Pixel);

            try
            {
                bitmap.Save(thumbnailPath, ImageFormat.Jpeg);
            }
            catch (Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }

[wartim]

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication9
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Bitmap Bmp = new Bitmap(pictureBox1.Image.Width * 4, pictureBox1.Image.Height * 4);
            Graphics G = Graphics.FromImage(Bmp);
            G.DrawImage(pictureBox1.Image, new Rectangle(new Point(0, 0), Bmp.Size));
            G.Dispose();
            pictureBox1.Image = Bmp;
        }
    }
}

[zgke]

使用Graphics把


pictureBox1.Image = Image.FromFile(@"C:\Temp\2.bmp");

int _Width = pictureBox1.Width * 4;
int _Height = pictureBox1.Height * 4;

Bitmap _ZoomBitmap = new Bitmap(_Width, _Height);
Graphics _Graphics = Graphics.FromImage(_ZoomBitmap);
_Graphics.DrawImage(pictureBox1.Image, 0, 0, _Width, _Height);
_Graphics.Dispose();

_ZoomBitmap.Save(@"C:\Temp\Zoom.bmp");

[Harvey_He]

楼上的都对

[guochanshan]

123楼的思路 都是一致的。

[GripVips]

这下可帮了我大帮了！ 试了一下三楼的方法 ！果然蛮简单的！