上传高质量图片处理为低质量但不能处理的太模糊

[wenblue]

用户有时候会上传4M以上的图片但是不能应为用户上传的图片质量大就提示不能上传，有没有什么方法可以把1M以上的图片处理到200k左右，但是不影响图片的显示效果（不能处理的太模糊）。

[wuyq11]

图片缩略图Image.GetThumbnailImage 方法：返回此 Image 的缩略图。
public Image GetThumbnailImage(
int thumbWidth,
int thumbHeight,
Image..::.GetThumbnailImageAbort callback,
IntPtr callbackData
)
Image thumbImg = Image.FromFile("").GetThumbnailImage(100, 120, null, new IntPtr());

Image img = Image.FromFile(path);
Bitmap bitmap = new Bitmap(100,100);
graphics g = graphics.fromimage(bitmap);
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
g.Clear(Color.Transparent);
g.drawimage(img,new rectangle(0,0,100,100),new rectangle(0,0,img.width,img.height))
bitmap.save(newpat,imageformat.jpeg)

[壹尘不染]

#region 压缩图片

        /// <summary>
        /// 压缩图片
        /// </summary>
        /// <param name="path">需要压缩的图片路径</param>
        /// <param name="newPath">压缩后的图片路径</param>
        /// <returns>是否压缩成功</returns>
        public bool ystp(string path, string newPath)
        {

            //是否压缩成功
            bool flag = false;

            string filePath = page.Server.MapPath(path);

            string filePath_ystp = page.Server.MapPath(newPath);
            //Bitmap   
            Bitmap bmp = null;

            //ImageCoderInfo    
            ImageCodecInfo ici = null;

            //Encoder   
            System.Drawing.Imaging.Encoder ecd = null;

            //EncoderParameter   
            EncoderParameter ept = null;

            //EncoderParameters   
            EncoderParameters eptS = null;

            try
            {
                bmp = new Bitmap(filePath);

                ici = this.getImageCoderInfo("image/jpeg");

                ecd = System.Drawing.Imaging.Encoder.Quality;

                eptS = new EncoderParameters(1);

                ept = new System.Drawing.Imaging.EncoderParameter(ecd, 10L);
                eptS.Param[0] = ept;
                bmp.Save(filePath_ystp, ici, eptS);
                flag = true;

            }
            catch (Exception)
            {

            }
            finally
            {
                bmp.Dispose();

                ept.Dispose();

                eptS.Dispose();
            }
            return flag;
        }

        /// <summary>   
        /// 获取图片编码类型信息   
        /// </summary>   
        /// <param name="coderType">编码类型</param>   
        /// <returns>ImageCodecInfo</returns>   
        private ImageCodecInfo getImageCoderInfo(string coderType)
        {
            ImageCodecInfo[] iciS = ImageCodecInfo.GetImageEncoders();

            ImageCodecInfo retIci = null;

            foreach (ImageCodecInfo ici in iciS)
            {
                if (ici.MimeType.Equals(coderType))
                    retIci = ici;
            }

            return retIci;
        }

        #endregion 压缩图片

[壹尘不染]

[Quote=引用 6 楼 xiaoxiangnanfoxmail 的回复:]
C# code

#region 压缩图片

/// <summary>
/// 压缩图片
/// </summary>
/// <param name="path">需要压缩的图片路径</param>
/// <param name="newPath">压缩后的图片路径</param>
……
[/Quote]
和你说下 用这个东西会改变图片的质量 使图片没原来的清晰 而且如果你上传的图片是GIF格式动画图片 那么经过这样处理之后就不能动了 不推荐这样处理 如果是列表页面要用的话你最好是把图片生成一张小的图片 如果是详细页面用的话最好是不要处理 你这样不紧会影响图片的质量 还会影响图片上传的速度

[jlds123]

限制上传大文件 用户自己处理

[hookyzlr]

 /// <summary>
    /// 生成缩略图
    /// </summary>
    /// <param name="originalImagePath">源图路径（物理路径）</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</param>    
    public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
    {
        System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

        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:
                break;
        }

        //新建一个bmp图片
        System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
        //新建一个画板
        System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
        //设置高质量插值法
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
        //设置高质量,低速度呈现平滑程度
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        //清空画布并以透明背景色填充
        g.Clear(System.Drawing.Color.Transparent);
        //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 System.Drawing.Rectangle(0, 0, towidth, toheight),
            new System.Drawing.Rectangle(x, y, ow, oh),
            System.Drawing.GraphicsUnit.Pixel);
        try
        {
            //以jpg格式保存缩略图
            bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        catch (System.Exception e)
        {
            throw e;
        }
        finally
        {
            originalImage.Dispose();
            bitmap.Dispose();
            g.Dispose();
        }
    }

[IHandler]

PS，另存时图片质量数选择低一点，另外可以按比例缩放一下

[ycproc]

这个 不太了解 只能 比率略缩了
不错 模糊了 效果 上就不好了
鱼和熊掌不能兼得

[chengfellow]

/// <summary>
        /// 生成指定尺寸的缩略图（以流的方式获取源文件）  
        /// </summary>
        /// <param name="fromFileStream">源图文件流</param>
        /// <param name="strFileName">文件名</param>
        /// <param name="templateWidth">模版宽</param>
        /// <param name="templateHeight">模版高</param>
        /// <returns>生成的缩略图流</returns>
        public MemoryStream MakeDesignationSizeThumbnail(System.IO.Stream fromFileStream, string strFileName, System.Double targetWidth, System.Double targetHeight) {
            //从文件取得图片对象，并使用流中嵌入的颜色管理信息  
            System.Drawing.Image originImg = System.Drawing.Image.FromStream(fromFileStream, true);
            System.Drawing.Image thumbnailImg = null;
            //宽、高  
            System.Double newWidth = originImg.Width, newHeight = originImg.Height;
            if (newWidth == targetWidth && newHeight == targetHeight) {
                thumbnailImg = originImg;
            }
            else {
                newWidth = targetWidth;
                newHeight = targetHeight;
                
                //取得图片大小  
                System.Drawing.Size mySize = new Size((int)newWidth, (int)newHeight);
                //新建一个bmp图片  
                thumbnailImg = new System.Drawing.Bitmap(mySize.Width, mySize.Height);
                //新建一个画板  
                System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(thumbnailImg);
                //设置高质量插值法  
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
                //设置高质量,低速度呈现平滑程度  
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                //清空一下画布  
                g.Clear(Color.White);
                //在指定位置画图  
                g.DrawImage(originImg, new System.Drawing.Rectangle(0, 0, thumbnailImg.Width, thumbnailImg.Height),
                new System.Drawing.Rectangle(0, 0, originImg.Width, originImg.Height),
                System.Drawing.GraphicsUnit.Pixel);

                g.Dispose();
            }

            MemoryStream stream = new MemoryStream();
            string strExt = System.IO.Path.GetExtension(strFileName);
            thumbnailImg.Save(stream, GetImageType(strExt));
            stream.Seek(0, SeekOrigin.Begin);
            originImg.Dispose();

            thumbnailImg.Dispose();

            return stream;
        }

[IHandler]

配置文件中可一设置上传文件的大小
web.config中:
<!-- 设置文件上传时的系统参数-->

<httpRuntime maxRequestLength="10240"
useFullyQualifiedRedirectUrl="true"
executionTimeout="6000"
minFreeThreads="8"
minLocalRequestFreeThreads="4"
appRequestQueueLimit="100"
/>