private static void TransferPixelsGreyscale(Bitmap bitmap_dest,
TwainDotNet.TwainNative.ImageInfo imageInfo, TwainDotNet.TwainNative.ImageMemXfer memxfer_src)
{
BitmapInfoHeaderIndexedColor bitmapInfo = new BitmapInfoHeaderIndexedColor();
bitmapInfo.Width = (int)memxfer_src.Columns;
bitmapInfo.Height = -(int)memxfer_src.Rows;
// bitmapInfo.Size = sizeof(BitmapInfoHeader); // requires unsafe
bitmapInfo.Size = 40; // the size of the initial header, not including color table
bitmapInfo.Planes = 1;
bitmapInfo.SizeImage = 0;
bitmapInfo.BitCount = imageInfo.BitsPerPixel;
if (imageInfo.Planar == (short)TwainNative.TwainBool.True)
{
throw new TwainException("Planar format invalid for greyscale data.");
}
if (imageInfo.BitsPerPixel == 8)
{
BitmapInfoHeaderIndexedColor.setupGreyscaleIndices(ref bitmapInfo);
bitmapInfo.ClrUsed = 256;
}
else if (imageInfo.BitsPerPixel == 1)
{
BitmapInfoHeaderIndexedColor.setupBWIndices(ref bitmapInfo);
bitmapInfo.ClrUsed = 2;
}
else
{
throw new TwainException("TransferPixelsGreyscale() only supports 8 bits per pixel");
}
using (Graphics graphics = Graphics.FromImage(bitmap_dest))
{
IntPtr hdc = graphics.GetHdc();
try
{
Gdi32Native.SetDIBitsToDevice(
hdc,
(int)memxfer_src.XOffset,
(int)memxfer_src.YOffset,
(int)memxfer_src.Columns,
(int)memxfer_src.Rows,
0, 0, 0,
(int)memxfer_src.Rows,
memxfer_src.Memory.TheMem,
bitmapInfo,
0);
}
finally
{
graphics.ReleaseHdc(hdc);
}
}
}
public static void setupGreyscaleIndices(ref BitmapInfoHeaderIndexedColor hdr)
{
// we use reflection to populate the greyscale table to avoid typing a giant hardcoded table
Object ohdr = hdr;
Type otype = hdr.GetType();
for (int i = 0; i < 256; i++)
{
var field = otype.GetField(String.Format("bmiColor_{0}", i), BindingFlags.Instance | BindingFlags.NonPublic);
field.SetValue(ohdr, new RGBQuad((byte)i, (byte)i, (byte)i));
}
hdr = (BitmapInfoHeaderIndexedColor)ohdr;
}
public static void setupBWIndices(ref BitmapInfoHeaderIndexedColor hdr)
{
hdr.bmiColor_0 = new RGBQuad(0, 0, 0); // black
hdr.bmiColor_1 = new RGBQuad(255, 255, 255); // white
}
public static extern int SetDIBitsToDevice(IntPtr hdc, int xdst, int ydst, int width, int height,
int xsrc, int ysrc, int start, int lines, IntPtr bitsptr, [In] BitmapInfoHeaderIndexedColor bmiptr, int colorUse);