使用矩形裁剪图片

Question

我想在c＃中裁剪图像。正如在大多数照片编辑软件中，我想使用可以通过鼠标调整大小和重新定位的矩形框。另外，我想知道如何突出裁剪区域，如this photo所示。

Answer 1

选择框的外部似乎有一个黑色的图像放置在它的约30％的alpha。为此，您只需将内容区域外的每个像素都绘制成一个黑色像素，并在其上面绘制一个30％的alpha值。这会产生所需的暗淡效果。

至于如何获得一个矩形在C＃中动态分页。

Answer 2

为了画出更亮或更暗的图片（或以任何方式更改颜色），请使用ColorMatrix，如this。

Answer 3

您的图像链接不再可用。

因此，假设在一个面板中你有你的图片框与图片裁剪。

首先，你需要创建事件处理程序的鼠标操作就能画出您希望裁剪矩形区域：

private void picBox_MouseDown(object sender, MouseEventArgs e) 
    { 
     Cursor = Cursors.Default; 
     if (Makeselection) 
     { 
      try 
      { 
       if (e.Button == System.Windows.Forms.MouseButtons.Left) 
       { 
        Cursor = Cursors.Cross; 
        cropX = e.X; 
        cropY = e.Y; 

        cropPen = new Pen(Color.Crimson, 1); 
        cropPen.DashStyle = DashStyle.Solid; 
       } 
       picBox.Refresh(); 
      } 
      catch (Exception ex) 
      { 
      } 
     } 
    } 

    private void picBox_MouseUp(object sender, MouseEventArgs e) 
    { 
     if (Makeselection) 
     { 
      Cursor = Cursors.Default; 
     } 
    } 

    private void picBox_MouseMove(object sender, MouseEventArgs e) 
    { 
     Cursor = Cursors.Default; 
     if (Makeselection) 
     { 
      picBox.Cursor = Cursors.Cross; 
      try 
      { 
       if (picBox.Image == null) 
        return; 


       if (e.Button == System.Windows.Forms.MouseButtons.Left) 
       { 
        picBox.Refresh(); 
        cropWidth = e.X - cropX; 
        cropHeight = e.Y - cropY; 
        picBox.CreateGraphics().DrawRectangle(cropPen, cropX, cropY, cropWidth, cropHeight); 
       } 
      } 
      catch (Exception ex) 
      { 
      } 
     } 
    } 

    private void picBox_MouseLeave(object sender, EventArgs e) 
    { 
     tabControl.Focus(); 
    } 

    private void picBox_MouseEnter(object sender, EventArgs e) 
    { 
     picBox.Focus(); 
    } 

现在，自带的按钮点击功能裁剪图像：

private void btnCrop_Click_1(object sender, EventArgs e) 
    { 
     Cursor = Cursors.Default; 

     try 
     { 
      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(picBoxScreenshot.Image, picBoxScreenshot.Width, picBoxScreenshot.Height); 
      //Original image 
      Bitmap _img = new Bitmap(cropWidth, cropHeight); 
      // for cropinfo 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); 

      picBox.Image = _img; 
      picBox.Width = _img.Width; 
      picBox.Height = _img.Height; 
      PictureBoxLocation(); 
      cropWidth = 0; 
     } 
     catch (Exception ex){} 
    } 

private void PictureBoxLocation() 
    { 
     int _x = 0; 
     int _y = 0; 
     if (panel1.Width > picBox.Width) 
     { 
      _x = (panel1.Width - picBox.Width)/2; 
     } 
     if (panel1.Height > picBox.Height) 
     { 
      _y = (panel1.Height - picBox.Height)/2; 
     } 
     picBox.Location = new Point(_x, _y); 
     picBox.Refresh(); 
    }