// ported form VB6 (Ctls\PortUtil\StdCtl.cpp:6176)
private unsafe bool DICopy(IntPtr hdcDest, IntPtr hdcSrc, RECT rect, bool bStretch)
{
long i;
// Get the bitmap from the DC by selecting in a 1x1 pixel temp bitmap
IntPtr hNullBitmap = SafeNativeMethods.CreateBitmap(1, 1, 1, 1, IntPtr.Zero);
if (hNullBitmap == IntPtr.Zero)
{
return(false);
}
try
{
IntPtr hBitmap = Gdi32.SelectObject(hdcSrc, hNullBitmap);
if (hBitmap == IntPtr.Zero)
{
return(false);
}
// Restore original bitmap
Gdi32.SelectObject(hdcSrc, hBitmap);
if (!Gdi32.GetObjectW(hBitmap, out Gdi32.BITMAP bmp))
{
return(false);
}
var lpbmi = new Gdi32.BITMAPINFO
{
bmiHeader = new Gdi32.BITMAPINFOHEADER
{
biSize = (uint)sizeof(Gdi32.BITMAPINFOHEADER),
biWidth = bmp.bmWidth,
biHeight = bmp.bmHeight,
biPlanes = 1,
biBitCount = bmp.bmBitsPixel,
biCompression = Gdi32.BI.RGB
},
bmiColors = new byte[Gdi32.BITMAPINFO.MaxColorSize * 4]
};
// Include the palette for 256 color bitmaps
long iColors = 1 << (bmp.bmBitsPixel * bmp.bmPlanes);
if (iColors <= 256)
{
byte[] aj = new byte[sizeof(Gdi32.PALETTEENTRY) * 256];
SafeNativeMethods.GetSystemPaletteEntries(hdcSrc, 0, (int)iColors, aj);
fixed(byte *pcolors = lpbmi.bmiColors)
{
fixed(byte *ppal = aj)
{
Gdi32.RGBQUAD * prgb = (Gdi32.RGBQUAD *)pcolors;
Gdi32.PALETTEENTRY *lppe = (Gdi32.PALETTEENTRY *)ppal;
// Convert the palette entries to RGB quad entries
for (i = 0; i < (int)iColors; i++)
{
prgb[i].rgbRed = lppe[i].peRed;
prgb[i].rgbBlue = lppe[i].peBlue;
prgb[i].rgbGreen = lppe[i].peGreen;
}
}
}
}
// Allocate memory to hold the bitmap bits
long bitsPerScanLine = bmp.bmBitsPixel * (long)bmp.bmWidth;
long bytesPerScanLine = (bitsPerScanLine + 7) / 8;
long totalBytesReqd = bytesPerScanLine * bmp.bmHeight;
byte[] lpBits = new byte[totalBytesReqd];
// Get the bitmap bits
int diRet = Gdi32.GetDIBits(
hdcSrc,
hBitmap,
0,
(uint)bmp.bmHeight,
lpBits,
ref lpbmi,
Gdi32.DIB.RGB_COLORS);
if (diRet == 0)
{
return(false);
}
// Set the destination coordiates depending on whether stretch-to-fit was chosen
int xDest, yDest, cxDest, cyDest;
if (bStretch)
{
xDest = rect.left;
yDest = rect.top;
cxDest = rect.right - rect.left;
cyDest = rect.bottom - rect.top;
}
else
{
xDest = rect.left;
yDest = rect.top;
cxDest = bmp.bmWidth;
cyDest = bmp.bmHeight;
}
// Paint the bitmap
int iRet = Gdi32.StretchDIBits(
hdcDest,
xDest,
yDest,
cxDest,
cyDest,
0,
0,
bmp.bmWidth,
bmp.bmHeight,
lpBits,
ref lpbmi,
Gdi32.DIB.RGB_COLORS,
Gdi32.ROP.SRCCOPY);
if (iRet == NativeMethods.GDI_ERROR)
{
return(false);
}
}
finally
{
Gdi32.DeleteObject(hNullBitmap);
}
return(true);
}
/// <summary>
/// Copies a bitmap into a 1bpp/8bpp bitmap of the same dimensions, very fast.
/// </summary>
/// <param name="bitmap">A <see cref="Bitmap"/> with the output bitmap.</param>
/// <param name="bitPerPixel">1 or 8, target bits per pixel.</param>
/// <returns>A <see cref="Bitmap"/> with a converted copy of the bitmap.</returns>
public static Bitmap CopyToBpp(Bitmap bitmap, int bitPerPixel)
{
if (bitPerPixel != 1 && bitPerPixel != 8)
{
throw new System.ArgumentException("1 or 8", "bpp");
}
// Plan: built into Windows GDI is the ability to convert
// bitmaps from one format to another. Most of the time, this
// job is actually done by the graphics hardware accelerator card
// and so is extremely fast. The rest of the time, the job is done by
// very fast native code.
// We will call into this GDI functionality from C#. Our plan:
// (1) Convert our Bitmap into a GDI hbitmap (ie. copy unmanaged->managed)
// (2) Create a GDI monochrome hbitmap
// (3) Use GDI "BitBlt" function to copy from hbitmap into monochrome (as above)
// (4) Convert the monochrone hbitmap into a Bitmap (ie. copy unmanaged->managed)
int w = bitmap.Width, h = bitmap.Height;
IntPtr hbm = bitmap.GetHbitmap(); // this is step (1)
// Step (2): create the monochrome bitmap.
// "BITMAPINFO" is an interop-struct which we define below.
// In GDI terms, it's a BITMAPHEADERINFO followed by an array of two RGBQUADs
Gdi32.BITMAPINFO bmi = new Gdi32.BITMAPINFO();
bmi.BiSize = 40; // the size of the BITMAPHEADERINFO struct
bmi.BiWidth = w;
bmi.BiHeight = h;
bmi.BiPlanes = 1; // "planes" are confusing. We always use just 1. Read MSDN for more info.
bmi.BiBitCount = (short)bitPerPixel; // ie. 1bpp or 8bpp
bmi.BiCompression = BIRGB; // ie. the pixels in our RGBQUAD table are stored as RGBs, not palette indexes
bmi.BiSizeImage = (uint)(((w + 7) & 0xFFFFFFF8) * h / 8);
bmi.BiXPelsPerMeter = 1000000; // not really important
bmi.BiYPelsPerMeter = 1000000; // not really important
// Now for the colour table.
uint ncols = (uint)1 << bitPerPixel; // 2 colours for 1bpp; 256 colours for 8bpp
bmi.BiClrUsed = ncols;
bmi.BiClrImportant = ncols;
bmi.Cols = new uint[256]; // The structure always has fixed size 256, even if we end up using fewer colours
if (bitPerPixel == 1)
{
bmi.Cols[0] = MAKERGB(0, 0, 0);
bmi.Cols[1] = MAKERGB(255, 255, 255);
}
else
{
for (int i = 0; i < 180; i++)
{
bmi.Cols[i] = MAKERGB(i, i, i);
}
}
// For 8bpp we've created an palette with just grayscale colours.
// You can set up any palette you want here. Here are some possibilities:
// greyscale: for (int i=0; i<256; i++) bmi.cols[i]=MAKERGB(i,i,i);
// rainbow: bmi.biClrUsed=216; bmi.biClrImportant=216; int[] colv=new int[6]{0,51,102,153,204,255};
// for (int i=0; i<216; i++) bmi.cols[i]=MAKERGB(colv[i/36],colv[(i/6)%6],colv[i%6]);
// optimal: a difficult topic: http://en.wikipedia.org/wiki/Color_quantization
//
// Now create the indexed bitmap "hbm0"
IntPtr bits0; // not used for our purposes. It returns a pointer to the raw bits that make up the bitmap.
IntPtr hbm0 = Gdi32.CreateDIBSection(
IntPtr.Zero,
ref bmi,
DIBRGBCOLORS,
out bits0,
IntPtr.Zero,
0);
// Step (3): use GDI's BitBlt function to copy from output hbitmap into monocrhome bitmap
// GDI programming is kind of confusing... nb. The GDI equivalent of "Graphics" is called a "DC".
IntPtr sdc = User32.GetDC(IntPtr.Zero); // First we obtain the DC for the screen
// Next, create a DC for the output hbitmap
IntPtr hdc = Gdi32.CreateCompatibleDC(sdc);
Gdi32.SelectObject(hdc, hbm);
// and create a DC for the monochrome hbitmap
IntPtr hdc0 = Gdi32.CreateCompatibleDC(sdc);
Gdi32.SelectObject(hdc0, hbm0);
// Now we can do the BitBlt:
Gdi32.BitBlt(hdc0, 0, 0, w, h, hdc, 0, 0, Gdi32.TernaryRasterOperations.SRCCOPY);
// Step (4): convert this monochrome hbitmap back into a Bitmap:
Bitmap b0 = Bitmap.FromHbitmap(hbm0);
// Finally some cleanup.
Gdi32.DeleteDC(hdc);
Gdi32.DeleteDC(hdc0);
User32.ReleaseDC(IntPtr.Zero, sdc);
Gdi32.DeleteObject(hbm);
Gdi32.DeleteObject(hbm0);
return(b0);
}
