C#图片按比例缩放

工具类代码：

using System;
 System.Collections.Generic;
 System.Drawing;
 System.Drawing.drawing2d;
 System.Drawing.Imaging;
 System.IO;
 System.Linq;
 System.Text;
 System.Threading.Tasks;

namespace ZoomImage.Utils
{
    /// <summary>
    /// 图片缩放
    </summary>
    public class ZoomImageUtil
    {
        #region 图片缩放
        <summary>
         图片缩放
        </summary>
        <param name="bArr">图片字节流</param>
        <param name="width">目标宽度，若为0，表示宽度按比例缩放<param name="height">目标长度，若为0，表示长度按比例缩放</param>
        static byte[] GetThumbnail(byte[] bArr,int width,1)">int height)
        {
            if (bArr == null) return null;
            MemoryStream ms = new MemoryStream(bArr);
            Bitmap bmp = (Bitmap)Image.FromStream(ms);
            ms.Close();

            bmp = GetThumbnail(bmp,width,height);

            ImageCodecInfo imageCodecInfo = GetEncoder(ImageFormat.Jpeg);
            EncoderParameters encoderParameters = new EncoderParameters(1);
            EncoderParameter encoderParameter = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality,75L);
            encoderParameters.Param[0] = encoderParameter;

            ms =  MemoryStream();
            bmp.Save(ms,imageCodecInfo,encoderParameters);
            byte[] result = ms.ToArray();
            ms.Close();
            bmp.dispose();

            return result;
        }
        #endregion

        <param name="bmp">图片private static Bitmap GetThumbnail(Bitmap bmp,1)">if (width == 0 && height == 0)
            {
                width = bmp.Width;
                height = bmp.Height;
            }
            else
            {
                )
                {
                    width = height * bmp.Width / bmp.Height;
                }
                if (height == )
                {
                    height = width * bmp.Height / bmp.Width;
                }
            }

            Image imgSource = bmp;
            Bitmap outBmp =  Bitmap(width,height);
            Graphics g = Graphics.FromImage(outBmp);
            g.Clear(Color.Transparent);
            // 设置画布的描绘质量     
            g.CompositingQuality = CompositingQuality.Default;
            g.SmoothingMode = SmoothingMode.Default;
            g.InterpolationMode = InterpolationMode.Default;
            g.DrawImage(imgSource,new Rectangle(0,height + 1),1)">,imgSource.Width,imgSource.Height,GraphicsUnit.Pixel);
            g.dispose();
            imgSource.dispose();
            bmp.dispose();
             outBmp;
        }
        #region 椭圆形缩放
         椭圆形缩放
        byte[] GetEllipseThumbnail( (Bitmap)Image.FromStream(ms);

            Bitmap newBmp = using (Graphics g = Graphics.FromImage(newBmp))
            {
                using (TextureBrush br =  TextureBrush(bmp))
                {
                    br.ScaleTransform(width / (float)bmp.Width,height / (float)bmp.Height);
                    g.SmoothingMode = System.Drawing.drawing2d.SmoothingMode.AntiAlias;
                    g.FillEllipse(br,1)">new Rectangle(Point.Empty,1)"> Size(width,height)));
                }
            }
            MemoryStream newMs =  MemoryStream();
            newBmp.Save(newMs,System.Drawing.Imaging.ImageFormat.Png);
             newMs.ToArray();

            bmp.dispose();
            newBmp.dispose();
            ms.Close();
            newMs.dispose();

            #region GetEncoder
        static ImageCodecInfo GetEncoder(ImageFormat format)
        {
            ImageCodecInfo[] codecs = ImageCodecInfo.Getimagedecoders();
            foreach (ImageCodecInfo codec in codecs)
            {
                if (codec.FormatID == format.Guid)
                {
                     codec;
                }
            }
            ;
        }
        #endregion

    }
}

View Code

使用示例：

 System.ComponentModel;
 System.Data;
 System.Threading;
 System.Threading.Tasks;
 System.Windows.Forms;
 ZoomImage.Utils;

 ZoomImage
{
    partial  Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        void Form1_Load(object sender,EventArgs e)
        {
            openFileDialog1.Multiselect = true;
        }

        void txtWidth_KeyPress(if (e.KeyChar != 8 && !Char.IsDigit(e.KeyChar))
            {
                e.Handled = ;
            }
        }

        void txtHeight_KeyPress(void btnSelectimage_Click(tryif (txtWidth.Text == "" && txtHeight.Text == "")
                {
                    MessageBox.Show("请输入宽度或高度！");
                    ;
                }

                if (openFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    Task.Factory.StartNew(() =>
                    {
                        
                        {
                            string path = Path.GetDirectoryName(openFileDialog1.FileNames[0]) + \\NewImage\\;
                            if (!Directory.Exists(path))
                            {
                                Directory.CreateDirectory(path);
                            }
                            foreach (string file  Directory.GetFiles(path))
                            {
                                File.Delete(file);
                            }

                            int i = string fileName  openFileDialog1.FileNames)
                            {
                                Bitmap bmp = ZoomImageUtil.GetThumbnail(new Bitmap(fileName),Convert.ToInt32(txtWidth.Text == "" ? 0" : txtWidth.Text),Convert.ToInt32(txtHeight.Text ==  : txtHeight.Text));

                                this.Invoke(new InvokeDelegate(() =>
                                {
                                    if (cbxExt.SelectedItem == )
                                    {
                                        bmp.Save(path + Path.GetFileName(fileName));
                                    }
                                    
                                    {
                                        bmp.Save(path + Path.GetFileNameWithoutExtension(fileName) + (string)cbxExt.SelectedItem);
                                    }
                                }));
                                
                                {
                                    lblProgress.Text = string.Format(进度：{1}/{0}",openFileDialog1.FileNames.Length,++i);
                                }));
                                Thread.Sleep();
                            }

                            MessageBox.Show(成功！);
                        }
                        catch (Exception ex)
                        {
                            MessageBox.Show(ex.Message);
                        }
                    });
                }
            }
             (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

    }

     跨线程访问控件的委托
    delegate void InvokeDelegate();
}

View Code