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ChangeViewPerspective Method
See Also  Example
Leadtools Namespace > RasterImage Class : ChangeViewPerspective Method



viewPerspective
Desired view perspective.
Rotates and flips the image data as necessary to achieve the desired view perspective.

Syntax

Visual Basic (Declaration) 
Public Sub ChangeViewPerspective( _
   ByVal viewPerspective As RasterViewPerspective _
)
Visual Basic (Usage)Copy Code
Dim instance As RasterImage
Dim viewPerspective As RasterViewPerspective
 
instance.ChangeViewPerspective(viewPerspective)
C# 
public void ChangeViewPerspective( 
   RasterViewPerspective viewPerspective
)
C++/CLI 
public:
void ChangeViewPerspective( 
   RasterViewPerspective viewPerspective
)

Parameters

viewPerspective
Desired view perspective.

Example

This example demonstrates the low-level methods for accessing 1-bit compressed image data. It demonstrates the ability to get and put rows, and the ability to process rows in buffer-to-buffer processing. The result of the function is an the first 50 lines are inverted.

Visual BasicCopy Code
Public Sub GetRowCompressedExample()
   RasterCodecs.Startup()
   Dim codecs As RasterCodecs = New RasterCodecs()
   ' Load the bitmap, at 1 bit per pixel, compressed
   codecs.Options.Load.Compressed = True
   Dim image As RasterImage = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "OCR1.TIF", 1, CodecsLoadByteOrder.Bgr, 1, 1)

   ' This example does not work with rotated view perspectives.
   If (image.ViewPerspective <> RasterViewPerspective.TopLeft) OrElse (image.ViewPerspective <> RasterViewPerspective.BottomLeft) Then
      image.ChangeViewPerspective(RasterViewPerspective.TopLeft)
   End If

   ' Adjust the YOffset if the view perspective is bottom left.
   Dim nRow As Integer = 500 ' first row to get.
   Dim nYSize As Integer = 500 ' number of rows to get.

   If image.ViewPerspective = RasterViewPerspective.BottomLeft Then
      nRow = image.Height - nRow - nYSize
   End If

   ' Allocate the buffers.
   Dim pBuffer As Byte() = New Byte(Convert.ToInt32((((image.Width + 31) And Not (31)) / 8)) * nYSize - 1) {} ' Buffer to hold the expanded row.
   Dim pRunBuffer As System.UInt16() = New System.UInt16(((image.Width + 3) * 2) * nYSize - 1) {} ' Buffer to hold the compressed row.

   If image.IsGlobalMemory Then
      image.Access()
   End If
   ' Get the top nRow lines.
   image.GetRowCompressed(Nothing, pRunBuffer, 0, nRow, nYSize)
   ' Expand the compressed data.
   RasterRleCompressor.ExpandRows(pRunBuffer, pBuffer, 0, image.Width, nYSize)
   ' Invert the data.

   Dim n As Integer = 0
   Do While n < (image.BytesPerLine * nYSize)
      pBuffer(n) = pBuffer(n) Xor Convert.ToByte(&HFF)
      n += 1
   Loop


   ' Compress the inverted data.
   RasterRleCompressor.CompressRows(pRunBuffer, pBuffer, 0, image.Width, nYSize)

   ' Put the inverted, compressed data back into the image.
   image.SetRowCompressed(Nothing, pRunBuffer, 0, nRow, nYSize)

   If image.IsGlobalMemory Then
      image.Release()
   End If

   codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "IMAGE1_getrowcompresed.BMP", RasterImageFormat.Bmp, 0)

   image.Dispose()
   codecs.Dispose()
   RasterCodecs.Shutdown()
End Sub
C#Copy Code
public void GetRowCompressedExample() 
{ 
   RasterCodecs.Startup(); 
   RasterCodecs codecs = new RasterCodecs(); 
   // Load the bitmap, at 1 bit per pixel, compressed 
   codecs.Options.Load.Compressed = true; 
   RasterImage image = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "OCR1.TIF", 1, Leadtools.Codecs.CodecsLoadByteOrder.Bgr, 1, 1); 
 
   // This example does not work with rotated view perspectives. 
   if((image.ViewPerspective != RasterViewPerspective.TopLeft) || (image.ViewPerspective != RasterViewPerspective.BottomLeft)) 
      image.ChangeViewPerspective(RasterViewPerspective.TopLeft); 
 
   // Adjust the YOffset if the view perspective is bottom left. 
   int nRow = 500; // first row to get. 
   int nYSize = 500; // number of rows to get. 
 
   if(image.ViewPerspective == RasterViewPerspective.BottomLeft) 
      nRow = image.Height - nRow - nYSize; 
 
   // Allocate the buffers. 
   byte[] pBuffer = new byte[Convert.ToInt32((((image.Width + 31) & ~(31)) / 8)) * nYSize]; // Buffer to hold the expanded row. 
   ushort[] pRunBuffer = new ushort[((image.Width + 3) * 2) * nYSize]; // Buffer to hold the compressed row. 
 
   if(image.IsGlobalMemory) 
      image.Access(); 
   // Get the top nRow lines. 
   image.GetRowCompressed(null, pRunBuffer, 0, nRow, nYSize); 
   // Expand the compressed data. 
   RasterRleCompressor.ExpandRows(pRunBuffer, pBuffer, 0, image.Width, nYSize); 
   // Invert the data. 
 
   for(int n = 0; n < (image.BytesPerLine * nYSize); n++) 
      pBuffer[n] ^= 0xff; 
 
 
   // Compress the inverted data. 
   RasterRleCompressor.CompressRows(pRunBuffer, pBuffer, 0, image.Width, nYSize); 
 
   // Put the inverted, compressed data back into the image. 
   image.SetRowCompressed(null, pRunBuffer, 0, nRow, nYSize); 
 
   if(image.IsGlobalMemory) 
      image.Release(); 
 
   codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "IMAGE1_getrowcompresed.BMP", RasterImageFormat.Bmp, 0); 
 
   image.Dispose(); 
   codecs.Dispose(); 
   RasterCodecs.Shutdown(); 
}

Remarks

The ViewPerspective is the arrangement of pixels in the image. This method references image coordinates, which are often different from the display coordinates of an image.

Use this method to change the data and the ViewPerspective to simplify calculations that involve image coordinates. This method does not affect the image display. For more information, refer to Accounting for View Perspective.

Requirements

Target Platforms: Microsoft .NET Framework 3.0, Windows XP, Windows Server 2003 family, Windows Server 2008 family

See Also