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RasterPaintDibInfo Class

Summary

This class describes the image data expected by the custom paint callbacks. It is used with the RasterPaintCallbacks callbacks.

Syntax

C++

public class RasterPaintDibInfo

Public Class RasterPaintDibInfo

public ref class RasterPaintDibInfo

Remarks

The user will typically allocate this class and return it from the RasterImagePaintCallbackFunction.GetDibInfoCallback callback.

Example

This example will show how to indicate that the graphics device expects a 16-bit image with the image data in the low 12 bits. Also, this particular card expected the data to be top-down, unlike the usual GDI functions which expect the data to be upside-down.

The example is in C++/CLI because this is the most useful language for implementing these classes.

// macro that calculates the number of bytes per line, rounding up to a multiple of 4 bytes 
#define DIB_WIDTH_BYTES(pixels) ((((pixels) + 31) & ~31) >> 3) 
              
Object^ myPaintCallbacks::GetDibInfoCallback(RasterImage^ image, array<Object^>^ args) 
{ 
   // make sure the parameters are correct 
   if(args->Length != 2 ||   image == nullptr) 
   { 
      throw gcnew RasterException(RasterExceptionCode::InvalidParameter); 
      return nullptr; 
   } 
   UInt32 uWidth = (UInt32)args[1]; 
   RasterPaintDibInfo^ pDibInfo = gcnew RasterPaintDibInfo; 
   if(pDibInfo == nullptr) 
   { 
      throw gcnew RasterException(RasterExceptionCode::NoMemory); 
      return nullptr; 
   } 
             
   pDibInfo->Default(); 
   pDibInfo->BitsPerPixel = 16;          // paint using 16-bit data, although there are only 12 significant bits 
   pDibInfo->PlaneCount = 1;             // One plane 
   pDibInfo->BytesPerLine = DIB_WIDTH_BYTES(uWidth * 16);   // bytes per line is a multiple of 4 bytes 
   pDibInfo->ViewPerspective = RasterViewPerspective::TopLeft; // the data should be TOP_LEFT, not BOTTOM_LEFT like the data in the regular GDI functions 
   pDibInfo->Order = RasterByteOrder::Gray;         // gray bitmap 
             
   // indicate that the data should be in the low 12 bits 
   pDibInfo->Flags = RasterPaintDibInfoFlags::LowHighBitValid; 
   pDibInfo->LowBit = 0; 
   pDibInfo->HighBit = 11; 
             
   return pDibInfo; 
}