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本文实例为大家分享了C#图片按比例缩放的具体代码，供大家参考，具体内容如下
工具类代码：
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ZoomImage.Utils
{
/// <summary>
/// 图片缩放
/// </summary>
public class ZoomImageUtil
{
/// <summary>
/// 图片缩放
/// </summary>
/// <param name="bmp">图片</param>
/// <param name="width">目标宽度，若为0，表示宽度按比例缩放</param>
/// <param name="height">目标长度，若为0，表示长度按比例缩放</param>
public static Bitmap GetThumbnail(Bitmap bmp, int width, int height)
{
if (width == 0)
{
width = height * bmp.Width / bmp.Height;
}
if (height == 0)
{
height = width * bmp.Height / bmp.Width;
}
Image imgSource = bmp;
Bitmap outBmp = new Bitmap(width, height);
Graphics g = Graphics.FromImage(outBmp);
g.Clear(Color.Transparent);
// 设置画布的描绘质量
g.CompositingQuality = CompositingQuality.HighQuality;
g.SmoothingMode = SmoothingMode.HighQuality;
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(imgSource, new Rectangle(0, 0, width, height + 1), 0, 0, imgSource.Width, imgSource.Height, GraphicsUnit.Pixel);
g.Dispose();
imgSource.Dispose();
bmp.Dispose();
return outBmp;
}
}
}
</div>
使用示例：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using ZoomImage.Utils;
namespace ZoomImage
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
openFileDialog1.Multiselect = true;
}
private void txtWidth_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar != 8 && !Char.IsDigit(e.KeyChar))
{
e.Handled = true;
}
}
private void txtHeight_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar != 8 && !Char.IsDigit(e.KeyChar))
{
e.Handled = true;
}
}
private void btnSelectImage_Click(object sender, EventArgs e)
{
try
{
if (txtWidth.Text == "" && txtHeight.Text == "")
{
return;
}
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
Task.Factory.StartNew(() =>
{
string path = Path.GetDirectoryName(openFileDialog1.FileNames[0]) + "\\NewImage\\";
int i = 0;
foreach (string fileName in openFileDialog1.FileNames)
{
Bitmap bmp = ZoomImageUtil.GetThumbnail(new Bitmap(fileName), Convert.ToInt32(txtWidth.Text == "" ? "0" : txtWidth.Text), Convert.ToInt32(txtHeight.Text == "" ? "0" : txtHeight.Text));
if (!Directory.Exists(path))
{
Directory.CreateDirectory(path);
}
File.Delete(path + Path.GetFileName(fileName));
bmp.Save(path + Path.GetFileName(fileName));
this.Invoke(new InvokeDelegate(() =>
{
lblProgress.Text = string.Format("进度：{1}/{0}", openFileDialog1.FileNames.Length, ++i);
}));
Thread.Sleep(1);
}
MessageBox.Show("成功！");
});
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
/// <summary>
/// 跨线程访问控件的委托
/// </summary>
public delegate void InvokeDelegate();
}
</div>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。