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; } }}

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();}

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。