如何减少C＃中的图像大小？

Question

我使用Graphics.DrawImage(DrawText())将DrawText拖拽到Image中。

问题是：我只绘制三个文字，但是原始图像的大小是：226kb，当Save（）〜3.45mb时输出图像。它太大了。

图片尺寸：2732 * 3200。

我只循环我的清单textFileSplit，而这个清单只有三个项目。

这是我所有的代码保存图像：

foreach (string text in lstTextFromFile) 
{ 
    count++; 
    if (text == "") continue; 
    Graphics gra = Graphics.FromImage(img); 
    string st = lstImgAdded.Items[k].Text; 
    Bitmap bmp = new Bitmap(@"" + st); 
    bmp = (Bitmap)ResizePanel(bmp, panel2); 
    panel2.BackgroundImage = bmp; 
    Graphics gbmp = Graphics.FromImage(bmp); 
    string[] textFileSplit = text.Split('-'); 
    for (int u = 0; u < textFileSplit.Count(); u++) 
    { 
     myColorLabel = activeLabels[u+1].ForeColor; 
     gbmp.DrawImage(
     DrawText(textFileSplit[u], fontType, myColorLabel, 
      Color.Transparent), 
     Point.Round(StretchImageSize(new Point(activeLabels[u+1].Location.X, activeLabels[u+1].Location.Y), panel2))); 
    } 
    gra.Dispose(); 
    Guid id = Guid.NewGuid(); 
    ScaleImage(bmp, witdhImg, heightImg) 
     .Save(linkLocation + "\\" + id + "." + imgType, 
      ImageFormat.Png); 
} 

在ScaleImage()类我试图保持尺寸一样出身图片：

public Image ScaleImage(Image image, int maxWidth, int maxHeight) 
{ 
    var ratioX = (double)maxWidth/image.Width; 
    var ratioY = (double)maxHeight/image.Height; 
    var ratio = Math.Min(ratioX, ratioY); 
    var ratio2 = Math.Max(ratioX, ratioY); 

    var newWidth = (int)(image.Width * ratio); 
    var newHeight = (int)(image.Height * ratio2); 

    var newImage = new Bitmap(newWidth, newHeight); 
    Graphics.FromImage(newImage).DrawImage(image, 0, 0, newWidth, newHeight); 
    return newImage; 
} 

Answer 1

确保设置分辨率和质量的尺度功能：

public Image ScaleImage(Image image, int maxWidth, int maxHeight) 
    { 
     var ratioX = (double)maxWidth/image.Width; 
     var ratioY = (double)maxHeight/image.Height; 
     var ratio = Math.Min(ratioX, ratioY); 
     var ratio2 = Math.Max(ratioX, ratioY); 

     var newWidth = (int)(image.Width * ratio); 
     var newHeight = (int)(image.Height * ratio2); 

     var newImage = var newImage = new Bitmap(newWidth, newHeight, image.PixelFormat); 
     newImage.SetResolution(image.HorizontalResolution, image.VerticalResolution); 

     Graphics grPhoto = Graphics.FromImage(newImage); 
     grPhoto.InterpolationMode = InterpolationMode.High; 

     grPhoto.DrawImage(image, 0, 0, newWidth, newHeight); 

     grPhoto.Dispose(); 
     return newImage;   
    } 

应用低质量的编码器参数：

ImageCodecInfo pngEncoder = ImageCodecInfo.GetImageDecoders().Where(k=> k.FormatID == ImageFormat.Png.Guid).First(); 
    EncoderParameters encoderParameters; 
    encoderParameters = new EncoderParameters(1); 
    encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, 60L); 
    ScaleImage(bmp, witdhImg, heightImg) 
    .Save(linkLocation + "\\" + id + "." + imgType, pngEncoder ,encoderParameters);