图片压缩

项目中有遇到限制图片大小得特定情况

将图片压缩至100K以下，转为base64输出

// 图片路径
private string getThumImage(string SourceFile)
        {
            try
            {
                //检测图片 是否要压缩 《 100k
                MemoryStream ms = new MemoryStream();
                Image img = Image.FromFile(SourceFile);
                img.Save(ms, img.RawFormat);
                if (ms.Length / 1024 <= 100)
                {
                    byte[] buffer = new byte[ms.Length];
                    ms.Position = 0;
                    ms.Read(buffer, 0, (int)ms.Length);
                    ms.Close();
                    return Convert.ToBase64String(buffer);
                }
                else
                {
                   // MemoryStream newms = new MemoryStream();
                    byte[] newbuffer = ms.ToArray();
                    // 压缩到 100 k 以下
                    string filetype = Path.GetExtension(SourceFile);
                    // 设置压缩比例
                    long imageQuality = ms.Length/1024/100;
                    Bitmap sourceImage = new Bitmap(img);
                    ImageCodecInfo myImageCodecInfo = GetImgEncoderIfo(filetype);//GetEncoderInfo("image/" + filetype);
                    System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
                  
                    while (newbuffer.Length / 1024 > 100) // 压缩后图片大小扔 大于100k 循环压缩
                    {
                        //imageQuality = newbuffer.Length / 1024 / 100;
                        imageQuality = ConvertType.ToInt64(Math.Ceiling(newbuffer.Length / 1024.0 / 100.0)); // 向上取整
                        EncoderParameters myEncoderParameters = new EncoderParameters(1);
                        EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, imageQuality);
                        myEncoderParameters.Param[0] = myEncoderParameter;
                        newbuffer = Compress(myEncoderParameters,myImageCodecInfo, sourceImage);
                    }
                    return Convert.ToBase64String(newbuffer);
                }
             
            }
            catch
            {
                return "";
            }
        }

 

 

压缩图片返回二进制字节：

public byte[] Compress(EncoderParameters myEncoderParameters, ImageCodecInfo myImageCodecInfo, Bitmap sourceImage)
        {
            try
            {
                // 防止图片过大  固定压缩未 1920*1080geshi
                float xWidth = 1920;// sourceImage.Width;
                float yWidth = 1080;// sourceImage.Height;
                Bitmap newImage = new Bitmap((int)xWidth, (int)yWidth);
                Graphics g = Graphics.FromImage(newImage);
                g.DrawImage(sourceImage, 0, 0, xWidth, yWidth );
                g.Dispose();
                //  newImage.Save(outputFile, myImageCodecInfo, myEncoderParameters);
                using (MemoryStream ms = new MemoryStream())
                {
                    newImage.Save(ms, myImageCodecInfo, myEncoderParameters);
                    byte[] buffer = ms.ToArray();
                    return buffer;
                }
            }
            catch (Exception ex)
            {
                return null;
            }
        }

 

/// <summary>
        /// 获取图片编码信息
        /// </summary>
        private ImageCodecInfo GetEncoderInfo(String mimeType)
        {
            int j;
            ImageCodecInfo[] encoders;
            encoders = ImageCodecInfo.GetImageEncoders();
            for (j = 0; j < encoders.Length; ++j)
            {
                if (encoders[j].MimeType == mimeType)
                    return encoders[j];
            }
            return null;
        }
        // 根据图片后缀（格式） 获取图片编码信息:(.jpg)
        private ImageCodecInfo GetImgEncoderIfo(string imgType)
        {
            try
            {
                ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders();
                for (int i = 0; i < encoders.Length; i++)
                {
                    if (encoders[i].FilenameExtension.Contains(imgType.ToUpper()))
                    {
                        return encoders[i];
                    }
                }
                return null;
            }
            catch
            {
                return null;
            }
        }

最后调用 getThumImage 方法 传入图片路径就行