Accessing pixel data using the RawBlocks object
To iterate through pixel blocks and pixel values to change the pixel values and persist the changes in the raster dataset using the RawBlocks object, see the following code example:
[C#]
public static void ReadWriteRawBlocks(IRasterDataset rasDs)
{
IRasterBandCollection rasBandCol = (IRasterBandCollection)rasDs;
IRawBlocks rawBlocks;
IRasterInfo rasInfo;
IPixelBlock pb;
// Iterate through each band of the dataset.
for (int m = 0; m <= rasBandCol.Count - 1; m++)
{
// QI to IRawBlocks from IRasterBandCollection.
rawBlocks = (IRawBlocks)rasBandCol.Item(m);
rasInfo = rawBlocks.RasterInfo;
// Create the pixel block.
pb = rawBlocks.CreatePixelBlock();
// Determine the tiling scheme for the raster dataset.
int bStartX = (int)Math.Floor((rasInfo.Extent.Envelope.XMin -
rasInfo.Origin.X) / (rasInfo.BlockWidth * rasInfo.CellSize.X));
int bEndX = (int)Math.Ceiling((rasInfo.Extent.Envelope.XMax -
rasInfo.Origin.X) / (rasInfo.BlockWidth * rasInfo.CellSize.X));
int bStartY = (int)Math.Floor((rasInfo.Origin.Y -
rasInfo.Extent.Envelope.YMax) / (rasInfo.BlockHeight *
rasInfo.CellSize.Y));
int bEndY = (int)Math.Ceiling((rasInfo.Origin.Y -
rasInfo.Extent.Envelope.YMin) / (rasInfo.BlockHeight *
rasInfo.CellSize.Y));
// Iterate through the pixel blocks.
for (int pbYcursor = startY; pbYcursor < endY; pbYcursor++)
{
for (int pbXcursor = startX; pbXcursor < endX; pbXcursor++)
{
// Get the pixel block.
rawBlocks.ReadBlock(pbXcursor, pbYcursor, 0, pb);
System.Array safeArray;
// Put the pixel block into a SafeArray for manipulation.
safeArray = (System.Array)pb.get_SafeArray(0);
// Iterate through the pixels in the pixel block.
for (int safeArrayHeight = 0; safeArrayHeight < pb.Height;
safeArrayHeight++)
{
for (int safeArrayWidth = 0; safeArrayWidth < pb.Width;
safeArrayWidth++)
{
// Use System.Array.SetValue to write the new pixel value back into the SafeArray.
safeArray.SetValue(Convert.ToByte(128), safeArrayWidth,
safeArrayHeight);
}
}
// Set the SafeArray back to the pixel block.
pb.set_SafeArray(0, safeArray);
// Write the pixel block back to the dataset.
rawBlocks.WriteBlock(pbXcursor, pbYcursor, 0, pb);
}
}
}
}
[VB.NET]
Public Sub ReadWriteRawBlocks(ByVal rasDs As IRasterDataset)
Dim rasBandCol As IRasterBandCollection
rasBandCol = rasDs
Dim rawBlocks As IRawBlocks
Dim rasInfo As IRasterInfo
Dim pb As IPixelBlock
' Iterate through each band of the dataset.
For m = 0 To rasBandCol.Count - 1
' QI to IRawBlocks from IRasterBandCollection.
rawBlocks = rasBandCol.Item(m)
rasInfo = rawBlocks.RasterInfo
' Create the pixel block.
pb = rawBlocks.CreatePixelBlock
' Determine the tiling scheme for the raster dataset.
Dim startX, startY, endX, endY As Integer
Dim bStartX As Integer = CInt(Math.Floor((rasInfo.Extent.Envelope.XMin - rasInfo.Origin.X) / _
(rasInfo.BlockWidth * rasInfo.CellSize.X)))
Dim bEndX As Integer = CInt(Math.Ceiling((rasInfo.Extent.Envelope.XMax - rasInfo.Origin.X) / _
(rasInfo.BlockWidth * rasInfo.CellSize.X)))
Dim bStartY As Integer = CInt(Math.Floor((rasInfo.Origin.Y - rasInfo.Extent.Envelope.YMax) / _
(rasInfo.BlockHeight * rasInfo.CellSize.Y)))
Dim bEndY As Integer = CInt(Math.Ceiling((rasInfo.Origin.Y - rasInfo.Extent.Envelope.YMin) / _
(rasInfo.BlockHeight * rasInfo.CellSize.Y)))
' Iterate through the pixel blocks.
For pbYcursor = startY To endY - 1
For pbXcursor = startX To endX - 1
' Get the pixel block.
rawBlocks.ReadBlock(pbXcursor, pbYcursor, 0, pb)
Dim safeArray As System.Array
' Put the pixel block into a SafeArray for manipulation.
safeArray = pb.SafeArray(0)
' Iterate through the pixels in the pixel block.
For safeArrayHeight = 0 To pb.Height
For safeArrayWidth = 0 To pb.Width
' Use System.Array.SetValue to write the new pixel value (128) back into the SafeArray.
safeArray.SetValue(CType(128, Byte), safeArrayWidth, safeArrayHeight)
Next
Next
' Set the SafeArray back to the pixel block.
pb.SafeArray(0) = safeArray
' Write the pixel block back to the dataset.
rawBlocks.WriteBlock(pbXcursor, pbYcursor, 0, pb)
Next
Next
Next
End Sub
See Also:
How to access pixel data using a raster cursorTo use the code in this topic, reference the following assemblies in your Visual Studio project. In the code files, you will need using (C#) or Imports (VB .NET) directives for the corresponding namespaces (given in parenthesis below if different from the assembly name):
ESRI.ArcGIS.System (ESRI.ArcGIS.esriSystem)ESRI.ArcGIS.Geodatabase ESRI.ArcGIS.Geometry ESRI.ArcGIS.DataSourcesRaster
Development licensing | Deployment licensing |
---|---|
ArcGIS for Desktop Basic | ArcGIS for Desktop Basic |
ArcGIS for Desktop Standard | ArcGIS for Desktop Standard |
ArcGIS for Desktop Advanced | ArcGIS for Desktop Advanced |
Engine Developer Kit | Engine |