winform按比例压缩图片

Question

winform压缩二进制图片

Answer 1

http://blog.sina.com.cn/s/blog_6427a6b50101el7v.html

Answer 2

上传并按比例生成高清略缩图图片
//按钮上传事件调用生成略缩图程序
  protected void btnUpload_Click(object sender, EventArgs e)
    {
        if (FileUploadImage.PostedFile.FileName != "")
        {
            //定义上传路径(在当前目录下的uploadfile文件下）
            string uploadpath = this.Server.MapPath("uploadfile");
            //取得文件名
            string tmpfilename = FileUploadImage.PostedFile.FileName;
            //文件名
            filename = tmpfilename.Substring(tmpfilename.LastIndexOf("\\") + 1);
            //原文件的保存路径
            string fileSavePath = uploadpath + "\\" + filename;
            //保存原图片            
            FileUploadImage.SaveAs(fileSavePath);
            //调用生成缩略图程序,生成缩略图及生成写字的图片
            this.toImage(FileUploadImage.PostedFile.InputStream, uploadpath, filename);
            //求取后缀名
            string suffix = filename.Substring(filename.LastIndexOf("."));
            //显示图片
            //分别为原图片/写字的图片(多一个w)/缩略图(多一个x)
            this.imgshow.ImageUrl = "~/uploadfile/" + filename;
            this.imgpri.ImageUrl = "~/uploadfile/" + filename.Replace(suffix, "w" + suffix);
            this.imgSmall.ImageUrl = "~/uploadfile/" + filename.Replace(suffix, "x" + suffix);
            //显示图像控件
            this.imgshow.Visible = true;
            this.imgpri.Visible = true;
            this.imgSmall.Visible = true;
        }  
    }
//生成略缩图程序
 private void toImage(Stream myStream, string uploadPath, string picName)
    {
        //取得后缀名
        string suffix = picName.Substring(picName.LastIndexOf("."));
        //缩略图的保存路径
        string fileXltPath = uploadPath + "\\" + picName.Replace(suffix, "x" + suffix);
        //写字图的保存路径
        string fileXztPath = uploadPath + "\\" + picName.Replace(suffix, "w" + suffix);
        //创建一个图像对象取得上传图片对象
        System.Drawing.Image myImage = System.Drawing.Image.FromStream(myStream, false);
        //对绘制前的图片产生一个缩略图(原图片一半大小)
        System.Drawing.Image thumbImage = myImage.GetThumbnailImage(myImage.Size.Width / 2, myImage.Size.Height / 2, null, System.IntPtr.Zero);
        //保存缩略图
        thumbImage.Save(fileXltPath, this.getImageFormat(suffix));
        //关闭缩略图对象
        thumbImage.Dispose();
           System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(myImage);
        g.DrawImage(myImage, 0, 0, myImage.Size.Width, myImage.Size.Height);
        //选择字体及字体大小
        System.Drawing.Font f = new Font("隶书", 40);
        //定义字体颜色
        System.Drawing.Brush b = new SolidBrush(System.Drawing.Color.Red);
        //开始绘制,根据上述两种设定,添加绘制的上左位置
        g.DrawString("远大宏图", f, b, 10, 10);
        //关闭绘制对象
        g.Dispose();
        //保存绘制后上传图片
        myImage.Save(fileXztPath, myImage.RawFormat);
        //关闭图片对象
        myImage.Dispose();
    }//CodeGo.net/
// 根据图片的后缀名,返回要保存的图片格式
 private System.Drawing.Imaging.ImageFormat getImageFormat(string suffix)
    {
        System.Drawing.Imaging.ImageFormat myFormat;
        switch (suffix.ToLower())
        {
            case ".bmp":
                myFormat = System.Drawing.Imaging.ImageFormat.Bmp;
                break;
            case ".emf":
                myFormat = System.Drawing.Imaging.ImageFormat.Emf;
                break;
            case ".exif":
                myFormat = System.Drawing.Imaging.ImageFormat.Exif;
                break;
            case ".gif":
                myFormat = System.Drawing.Imaging.ImageFormat.Gif;
                break;
            case ".icon":
                myFormat = System.Drawing.Imaging.ImageFormat.Icon;
                break;
            case ".jpeg":
            case ".jpg":
                myFormat = System.Drawing.Imaging.ImageFormat.Jpeg;
                break;
            case ".png":
                myFormat = System.Drawing.Imaging.ImageFormat.Png;
                break;
            case ".tiff":
                myFormat = System.Drawing.Imaging.ImageFormat.Tiff;
                break;
            case ".wmf":
                myFormat = System.Drawing.Imaging.ImageFormat.Wmf;
                break;
            default:
                myFormat = System.Drawing.Imaging.ImageFormat.MemoryBmp;
                break;
        }
        return (myFormat);

Answer 3

上面的要求有两个：1）固定的大小 2）图片按比例缩小或扩大
固定的大小存在三种情况：高>宽  高<宽 高=宽
添加的图片也存在三种情况：高>宽  高<宽 高=宽
解决方法是比较固定大小的宽高比例和图片宽高比例//image为源图片，w为固定的宽，h为固定的高
private Image GetSizeImage(Image image, int w, int h)
        {
            double pCtrl = (double)w / (double)h;//固定的宽高比例
            double pImg = (double)image.Width / (double)image.Height;//图片宽高比例            Image  newImage;
            if (pCtrl > pImg) {
                if (h < image.Height) {
                    newImage = drawImage(image, (int)(h * pImg), h);
                } else {
                    newImage = drawImage(image, image.Width, image.Height);
                }
            } else if (pCtrl < pImg) {
                if (image.Width > w) {
                    newImage  = drawImage(image, w, (int)(w / pImg));
                } else {
                    newImage  = drawImage(image, image.Width, image.Height);
                }
            } else {
                if (image.Width > w) {
                    newImage  = drawImage(image,w, h);
                } else {
                    newImage  = drawImage(image, image.Width, image.Height);
                }
            }            return newImage ;
        }
  
private Image drawImage(Image sourceImage, int width, int height)
        {
            Image bitmap = new Bitmap(width, height);
            Graphics img = Graphics.FromImage(bitmap);
            img.CompositingQuality = CompositingQuality.HighQuality;
            img.SmoothingMode = SmoothingMode.HighQuality;
            img.InterpolationMode = InterpolationMode.High;
            img.DrawImage(sourceImage, new Rectangle(0, 0, width, height));           return bitmap ;
        }