提高图像的打印质量

Question

我在写一个需要打印高分辨率.tiff图像的程序。我遇到的问题是我无法打印质量很好的.tiff文件。由于.tiff的大尺寸（例如8700x7200），它不适合任何标准尺寸的纸张。我试图增加新闻部，但似乎没有任何影响。我可以让.tiff适合页面的唯一方法就是缩小它。但那时图像质量可怕。 （我将其缩小到适合11x17，但只有1100x1700的指示分辨率）。我试着改变打印机上的分辨率，尝试手动和编程设置打印机的质量/分辨率，但没有成功。基本上我希望能够将更多的.tiff像素放到11x17页面上，所以我不需要增加比例。我认为增加打印dpi会增加11x17英寸的像素数量，但是我看不到任何效果。也许我做错了什么。任何帮助将不胜感激。谢谢。

下面的代码是我正在尝试执行pd.Print（）时调用。

private void pd_PrintPage(object sender, PrintPageEventArgs ev) 
    { 
     //float x = ev.MarginBounds.Left; 
     //float y = ev.MarginBounds.Top; 
     try 
     { 
      //ResizeImage(@"H:\21RR-G0K-30140-0220-0002.tiff", @"H:\21RR-G0K-30140-0220-0002-new.tiff", 500, 900, false); 
      Image tempImage = Image.FromFile(@"H:\21RR-G0K-30140-0220-0002.tiff"); 
      Bitmap bMap = new Bitmap(tempImage); 
      bMap.SetResolution(1200, 1200); 
      string l = ""; 
      tempImage = bMap; 
      /*if (tempImage.Width > tempImage.Height) //if poster is longer then it is tall, rotate the image. Done to match standard printing aspect ratios 
      { 
       Bitmap tempBitmap = new Bitmap(tempImage); //Need to convert to Bitmap type to do rotation 
       RotateBicubic rotationFilter = new RotateBicubic(90, true); 
       tempImage = rotationFilter.Apply(tempBitmap); 
      }*/ 
      float ImageAspectRatio = (float)tempImage.Height/(float)tempImage.Width; 
      float PageSizeAspectRatio = (float)_pSize.Height/(float)_pSize.Width; //_pSize is the selected printing sheet size 
      if (ImageAspectRatio < 1 && PageSizeAspectRatio > 1) //Need to rotate Image. Can't attempt to rotate tempImage due to size. Scale then rotate. 
      { 
       double x_scale = (double)_pSize.Width/(double)tempImage.Height; 
       double y_scale = (double)_pSize.Height/(double)tempImage.Width; 
       int percent = 0; 
       if (y_scale < x_scale) 
       { 
        percent = Convert.ToInt32(y_scale * 100); 
       } 
       else 
       { 
        percent = Convert.ToInt32(x_scale * 100); 
       } 
       Image myImage = ImageManipulation.ScaleByPercent(tempImage, percent); //I know this line is the problem, but I can't fit the image on the page without massive scaling due to the page reolution restraints 
       Bitmap tempMap = new Bitmap(myImage); 
       tempMap.SetResolution(1200, 1200); 
       RotateBicubic rotateBC = new RotateBicubic(90); 
       Image finalImage = rotateBC.Apply(tempMap); //rotate the image 90 degrees using bicubic interpolation. This isn't what's killing the quality as the quality is no better with this disabled 
       ev.Graphics.DrawImage(finalImage, 0, 0); 
      } 
      else if (ImageAspectRatio >= 1 && PageSizeAspectRatio >= 1) //No Need for rotation 
      { 
       double x_scale = (double)_pSize.Width/(double)tempImage.Width; 
       double y_scale = (double)_pSize.Height/(double)tempImage.Height; 
       int percent = 0; 
       if (y_scale < x_scale) 
       { 
        percent = Convert.ToInt32(y_scale * 100); 
       } 
       else 
       { 
        percent = Convert.ToInt32(x_scale * 100); 
       } 

       Image myImage = ImageManipulation.ScaleByPercent(tempImage, percent); 
       ev.Graphics.DrawImage(myImage, 0, 0); 

      } 

      else 
      { 

      }    
     } 
     catch(Exception ex) 
     { 
      string breakingpoint = ""; 
     } 
    } 

Answer 1

您正在寻找的术语是“重采样”。

它也可能是最好的使用设备坐标系或GDI + HIENGLISH单位（我认为这就是对打印设备上下文中使用。）

使用的DrawImage命令你要最好的缩放图像从GDI +获得的是HighQualityBicubic Resampling。

    Private Sub pd_PrintPage(ByVal sender As System.Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) Handles pd.PrintPage 

     Dim img As Image = Image.FromFile("SAMPLE.TIF") 

     Dim imageWidth As Integer = CInt((img.Width/img.HorizontalResolution) * 100) 
     Dim imageHeight As Integer = CInt((img.Height/img.VerticalResolution) * 100) 

     If imageWidth > e.PageBounds.Width Then 
      Dim ratio As Double = imageWidth/imageHeight 
      imageWidth = e.PageBounds.Width 
      If ratio < 1 Then 
       imageHeight = CInt(imageWidth * ratio) 
      Else 
       imageHeight = CInt(imageWidth/ratio) 
      End If 
     End If 

     If imageHeight > e.PageBounds.Height Then 
      Dim ratio As Double = imageHeight/imageWidth 
      imageHeight = e.PageBounds.Height 
      If ratio < 1 Then 
       imageWidth = CInt(imageHeight * ratio) 
      Else 
       imageWidth = CInt(imageHeight/ratio) 
      End If 
     End If 

     e.Graphics.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic 
     e.Graphics.DrawImage(img, 0, 0, imageWidth, imageHeight) 

    End Sub 

Answer 2

看来问题出在缩放例程中。也许你应该研究一些包含高质量缩放算法的第三方库。