Retrieves (into an unmanaged memory buffer) a row (or part of a row) of 1-bit compressed data from an image that
has been loaded in its compressed format.
Syntax
| Visual Basic (Usage) |  Copy Code |
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Dim instance As RasterImage
Dim workBuffer As IntPtr
Dim runBuffer As IntPtr
Dim row As Integer
Dim column As Integer
Dim width As Integer
Dim value As Integer
value = instance.GetRowColumnCompressed(workBuffer, runBuffer, row, column, width)
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Parameters
- workBuffer
- Pointer to optional unmanaged memory work buffer. Allocating the work buffer speeds
processing if you call this method more than once, because if you do not allocate a work buffer, the method
allocates and frees a temporary buffer each time it is called. The size of this buffer should be the same as the
BytesPerLine property. Pass IntPtr.Zero for workBuffer if you do not want to use
the work buffer
- runBuffer
- Pointer to the output unmanaged memory buffer, which will be filled with 1-bit compressed image data.
Calculate the required size of this buffer as follows: bytes required = (Width + 3) * 2.
- row
- The number of the row to retrieve. The first row is 0, and the last row is 1 less than the image
height.
- column
- The column offset within the row to retrieve. The first column offset is 0, and the last column
offset is 1 less than the image width.
- width
- The number of pixels to retrieve.
Return Value
The number of pixels processed.
Example
This example demonstrates the low-level methods for accessing 1-bit compressed bitmap data.
It demonstrates the ability to get and set partial rows, and the ability to process partial rows in
buffer-to-buffer processing. The result of the method is an inverted rectangle in the middle of the image.
| Visual Basic | Copy Code |
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Public Sub GetRowColumnCompressedExample()
RasterCodecs.Startup()
Dim codecs As RasterCodecs = New RasterCodecs()
codecs.Options.Load.Compressed = True
Dim image As RasterImage = codecs.Load(LeadtoolsExamples.Common.ImagesPath.Path + "OCR1.TIF", 1, CodecsLoadByteOrder.Bgr, 1, 1)
Dim xOffset As Integer
Dim xSize As Integer
Dim yOffset As Integer
Dim ySize As Integer
Dim i, n As Integer
Dim buffer As Byte()
Dim runBuffer As System.UInt16()
Dim workBuffer As Byte()
If (image.ViewPerspective <> RasterViewPerspective.TopLeft) OrElse (image.ViewPerspective <> RasterViewPerspective.BottomLeft) Then
image.ChangeViewPerspective(RasterViewPerspective.TopLeft)
End If
xOffset = image.Width \ 3
xSize = image.Width - xOffset
yOffset = image.Height \ 3
ySize = image.Height \ 3
If image.ViewPerspective = RasterViewPerspective.BottomLeft Then
yOffset = image.Height - yOffset - ySize
End If
If image.IsGlobalMemory Then
image.Access()
End If
buffer = New Byte((xSize + 7) \ 8 - 1) {}
runBuffer = New System.UInt16((xSize + 3) * 2 - 1) {}
workBuffer = New Byte(image.BytesPerLine - 1) {}
i = yOffset
Do While i < (yOffset + ySize)
image.GetRowColumnCompressed(workBuffer, runBuffer, 0, i, xOffset, xSize)
RasterRleCompressor.ExpandRow(runBuffer, buffer, 0, 0, xSize)
n = 0
Do While n < (xSize / 16)
buffer(n) = buffer(n) Xor Convert.ToByte(&HFF)
n += 1
Loop
RasterRleCompressor.CompressRow(runBuffer, buffer, 0, 0, xSize)
image.SetRowColumnCompressed(workBuffer, runBuffer, 0, i, xOffset, xSize)
i += 1
Loop
If image.IsGlobalMemory Then
image.Release()
End If
codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "IMAGE1_getrowcolcompresed.BMP", RasterImageFormat.Bmp, 0)
image.Dispose()
codecs.Dispose()
RasterCodecs.Shutdown()
End Sub |
| C# | Copy Code |
|---|
public void GetRowColumnCompressedExample()
{
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);
int xOffset; // Column offset of the rectangle to process.
int xSize; // Pixel width of the rectangle to process.
int yOffset; // Row offset of the rectangle to process.
int ySize; // Pixel height of the rectangle to process.
int i, n; // Counters.
byte[] buffer; // Buffer to hold the expanded row.
ushort[] runBuffer; // Buffer to hold the compressed row.
byte[] workBuffer; // Work buffer.
// This example does not work with rotated view perspectives.
if((image.ViewPerspective != RasterViewPerspective.TopLeft) || (image.ViewPerspective != RasterViewPerspective.BottomLeft))
image.ChangeViewPerspective(RasterViewPerspective.TopLeft);
// Specify a rectangle in the middle right part of the displayed image.
xOffset = image.Width / 3;
xSize = image.Width - xOffset;
yOffset = image.Height / 3;
ySize = image.Height / 3;
// Adjust the YOffset if the view perspective is bottom left.
if(image.ViewPerspective == RasterViewPerspective.BottomLeft)
{
yOffset = image.Height - yOffset - ySize;
}
if(image.IsGlobalMemory)
image.Access();
// Allocate the buffers.
buffer = new Byte[(xSize + 7) / 8];
runBuffer = new ushort[(xSize + 3) * 2];
workBuffer = new Byte[image.BytesPerLine];
// Invert the colors of pixels in the left half of the rectangle.
// Notice that we get the whole rectangle, but process only half of it.
for(i = yOffset; i < (yOffset + ySize); i++)
{
image.GetRowColumnCompressed(workBuffer, runBuffer, 0, i, xOffset, xSize);
RasterRleCompressor.ExpandRow(runBuffer, buffer, 0, 0, xSize);
for(n = 0; n < (xSize / 16); n++)
buffer[n] ^= 0xFF;
RasterRleCompressor.CompressRow(runBuffer, buffer, 0, 0, xSize);
image.SetRowColumnCompressed(workBuffer, runBuffer, 0, i, xOffset, xSize);
}
if(image.IsGlobalMemory)
image.Release();
codecs.Save(image, LeadtoolsExamples.Common.ImagesPath.Path + "IMAGE1_getrowcolcompresed.BMP", RasterImageFormat.Bmp, 0);
image.Dispose();
codecs.Dispose();
RasterCodecs.Shutdown();
} |
Remarks
Requirements
Target Platforms: Microsoft .NET Framework 3.0, Windows XP, Windows Server 2003 family, Windows Server 2008 family
See Also
