在C#中无失真的裁剪和打印图像文档

Question

我正在使用WinForms.在我的表格中,我有一个用于显示图像文档的图片框.问题是当我裁剪图像然后打印文档时图像变得稍微扭曲.如果我不裁剪图像文档并定期打印,图像文档不会变形.

如何裁剪和打印图像文档而不会使图像文档失真？

或者是否有更好的方法来编码,以便它可以裁剪和打印而不会使图像文档失真？如果是这样,我该怎么办？

笔记:

• 我的图片框设置为缩放,因为我使用的图像很大:

• 图像文档示例尺寸:2500 x 3100

• 我的图片框没有边框

  int _cropX, _cropY, _cropWidth, _cropHeight;
  public Pen _cropPen;
  private State _currentState;
  
  private enum State
  {
      Crop
  }
  
  private void Open_btn_Click(object sender, EventArgs e)
  {
      // open file dialog 
      OpenFileDialog open = new OpenFileDialog();
  
      if (open.ShowDialog() == DialogResult.OK)
      {
          // display image in picture box
          pictureBox1.Image = new Bitmap(open.FileName);
      }
  }
  
  private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
  {
      try
      {
          if (Crop_Checkbox.Checked == true)
          {
              Cursor = Cursors.Default;
              if (_currentState == State.Crop)
              {
                  if (_cropWidth < 1)
                  {
                      return;
                  }
  
                  Rectangle rect = new Rectangle(_cropX, _cropY, _cropWidth, _cropHeight);
                  //First we define a rectangle with the help of already calculated points
  
                  Bitmap originalImage = new Bitmap(pictureBox1.Image, pictureBox1.Width, pictureBox1.Height);
                  //Original image
  
                  Bitmap img = new Bitmap(_cropWidth, _cropHeight);
                  // for cropinf image
  
                  Graphics g = Graphics.FromImage(img);
                  // create graphics
  
                  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                  g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
                  g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                  //set image attributes
  
                  g.DrawImage(originalImage, 0, 0, rect, GraphicsUnit.Pixel);
  
                  pictureBox1.Image = img;
                  pictureBox1.Width = img.Width;
                  pictureBox1.Height = img.Height;
              }
  
          }
          else
          {
              Cursor = Cursors.Default;
          }
      }
      catch (Exception)
      {
  
      }
  }
  
  private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
  {
      if (Crop_Checkbox.Checked == true)
      {
          if (_currentState == State.Crop)
          {
              Cursor = Cursors.Cross;
              if (e.Button == System.Windows.Forms.MouseButtons.Left)
              {
                  //X and Y are the coordinates of Crop
                  pictureBox1.Refresh();
                  _cropWidth = e.X - _cropX;
                  _cropHeight = e.Y - _cropY;
                  pictureBox1.CreateGraphics().DrawRectangle(_cropPen, _cropX, _cropY, _cropWidth, _cropHeight);
              }
  
          }
      }
      else
      {
          Cursor = Cursors.Default;
      }
  
  }
  
  private void Crop_Checkbox_CheckedChanged(object sender, EventArgs e)
  {
      if (Crop_Checkbox.Checked == true)
      {
          this.Cursor = Cursors.Cross;
      }
  }
  
  private void Print_btn_Click(object sender, EventArgs e)
  {
      System.Drawing.Printing.PrintDocument myPrintDocument1 = new System.Drawing.Printing.PrintDocument();
      PrintDialog myPrinDialog1 = new PrintDialog();
      myPrintDocument1.PrintPage += new System.Drawing.Printing.PrintPageEventHandler(printDocument1_PrintPage);
      myPrinDialog1.Document = myPrintDocument1;
  
  
      if (myPrinDialog1.ShowDialog() == DialogResult.OK)
      {
          myPrintDocument1.Print();
      }
  }
  
  private void printDocument1_PrintPage(object sender, PrintPageEventArgs e)
  {
      e.Graphics.DrawImage(pictureBox1.Image, 10, 10); //(Standard paper size is 850 x 1100 or 2550 x 3300 pixels)
  }
  
  private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
  {
      if (Crop_Checkbox.Checked == true)
      {
          if (_currentState == State.Crop)
          {
              if (e.Button == System.Windows.Forms.MouseButtons.Left)
              {
                  Cursor = Cursors.Cross;
                  _cropX = e.X;
                  _cropY = e.Y;
  
                  _cropPen = new Pen(Color.FromArgb(153, 180, 209), 3); //2 is Thickness of line
  
                  _cropPen.DashStyle = DashStyle.DashDotDot;
                  pictureBox1.Refresh();
              }
          }
      }
      else
      {
          Cursor = Cursors.Default;
      }
  
  }
  

测试:略有失真:

测试:未扭曲:

测试: 上面的图片是一个测试.这是当我从pictureBox1_MouseUp中取出以下代码时发生的事情:

Bitmap originalImage = new Bitmap(pictureBox1.Image, pictureBox1.Width, pictureBox1.Height);

并编辑/替换(originalImage to pictureBox1.Image):

g.DrawImage(pictureBox1.Image, 0, 0, rect, GraphicsUnit.Pixel);

Answer 1

Bitmap originalImage = new Bitmap(pictureBox1.Image, pictureBox1.Width, pictureBox1.Height);

这很可能就是问题开始的地方。这可能会导致 pictureBox1.Image 重新缩放以强制适合 pictureBox1 大小。取决于图片框是否有边框及其 SizeMode 属性值。重新缩放会导致图像重新采样，新位图中像素的颜色是根据所选插值模式的指示，根据原始图像中其相邻像素的值计算的。

这实际上模糊了生成的图像。这在照片上效果很好，但这种文本在很大程度上取决于抗锯齿像素，才能在低分辨率显示器上看起来不错。对这些像素的轻微更改会破坏效果，并且它们不再将字母形状与背景平滑地混合。它们变得更加明显，最好的描述方式是生成的文本看起来“胖”。

我在发布的代码中根本看不到这样做的明显理由。删除该语句并将originalImage替换为pictureBox1.Image.

另请注意，打印此图像可能会令人失望。现在，这些抗锯齿像素变成了纸上 6x6 的墨水斑点。只有当你有长手臂时，这才看起来不错。只要字体这么小，并且您无法控制抗锯齿选项，那么您就无能为力。仅当您使用 PrintDocument 和 Graphics.DrawString() 时，打印文本才会看起来不错。