GDI

Local

• Bitmaps
• Brushes
• DDB (Device Dependant Bitmaps)
• Functions
• Pixel Color, of a Desktop pixel
• Releasing
• Using an Object

External

• cursors

Bitmap, Reading one from a file

• Use ::LoadImage
• Select the image into a DC to get the palette (if it has one)

See also How To Use LoadImage() to Read a BMP file (with pallette support)

*pIconHandle = 0;

HBITMAP hbitmap;
hbitmap = (HBITMAP)LoadImage(0, filename, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE|LR_CREATEDIBSECTION|LR_DEFAULTSIZE);
if ( hbitmap == 0) {
	return E_FAIL;
}

DIBSECTION dibSection;
if ( ::GetObject( hbitmap, sizeof(dibSection), &dibSection) == 0) {
	::DeleteObject( hbitmap);
	return E_FAIL;
}

HDC hdcDisplay	= ::CreateDC( _T("DISPLAY"), NULL, NULL, NULL);
HDC hdcBitmap	= ::CreateCompatibleDC( hdcDisplay);

BITMAPINFO *pSrcBmi = (BITMAPINFO*)(new char[ sizeof(*pSrcBmi) + 4 * 256]);
memcpy( pSrcBmi, &(dibSection.dsBmih), sizeof(pSrcBmi->bmiHeader));

if ( dibSection.dsBm.bmBitsPixel * dibSection.dsBm.bmPlanes <= 8) {
	// has a palette
	HDC				hMemDc;
	HBITMAP			hOldBitmap;
	RGBQUAD			rgb[256];

	hMemDc = CreateCompatibleDC( NULL);
	hOldBitmap = (HBITMAP)::SelectObject( hMemDc, hbitmap);
	GetDIBColorTable( hMemDc, 0, 256, rgb);

	for ( int i = 0; i < 256; i++) {
		pSrcBmi->bmiColors[i].rgbRed	= rgb[i].rgbRed;
		pSrcBmi->bmiColors[i].rgbGreen	= rgb[i].rgbGreen;
		pSrcBmi->bmiColors[i].rgbBlue	= rgb[i].rgbBlue;
		pSrcBmi->bmiColors[i].rgbReserved = 0;
	}

	::SelectObject( hMemDc, hOldBitmap);
	DeleteDC( hMemDc);
}

BITMAPINFO targetBmi;
ZeroMemory( &targetBmi, sizeof(targetBmi));
targetBmi.bmiHeader.biSize = sizeof(targetBmi);
targetBmi.bmiHeader.biWidth = dibSection.dsBm.bmWidth;
targetBmi.bmiHeader.biHeight = dibSection.dsBm.bmHeight;
targetBmi.bmiHeader.biPlanes = 1;
targetBmi.bmiHeader.biBitCount = 32;

unsigned char *pDibData = 0;
HBITMAP hBitDib;
hBitDib = ::CreateDIBSection( hdcBitmap, &targetBmi, DIB_RGB_COLORS, (void**)(&pDibData), NULL, 0);
HGDIOBJ tmpObj = ::SelectObject( hdcBitmap, hBitDib);

int retcode;
retcode = StretchDIBits(
	hdcBitmap,
	0,0,
	dibSection.dsBm.bmWidth,
	dibSection.dsBm.bmHeight,
	0,0,
	dibSection.dsBm.bmWidth,
	dibSection.dsBm.bmHeight,
	dibSection.dsBm.bmBits,
	pSrcBmi,
	DIB_RGB_COLORS,
	SRCCOPY
	);

// pDibData now contains the 32 bit pixel data from the bmp

::SelectObject( hdcBitmap, tmpObj);
::DeleteObject( hBitDib);

::ReleaseDC( NULL, hdcBitmap);
::ReleaseDC( NULL, hdcDisplay);

::DeleteObject( hbitmap);

*pIconHandle = m_pSS->m_handleManager.GetNextHandle( pBit);

return S_OK;

Pixel Color, of a Desktop pixel

HDC hdcDesktop = ::CreateDC( _T("DISPLAY"), NULL, NULL, NULL);
COLORREF color;
color = ::GetPixel( hdcDesktop, int xPosLogical, int yPosLogical);
::DeleteDC( hdcDesktop);

Brushes

HBRUSH hBrush = ::CreateSolidBrush( RGB(0xff, 0x7f, 0x00));
HBRUSH hOld = ::SelectObject( hDc, hBrush);

// Use it Here ...

::SelectObject( hDc, hOld);
::DeleteObject( hBrush);

Bitmap in Memory (DIBSection)

HBITMAP hBitDib;

// Get the display DC
HDC hddc = ::CreateDC( _T("DISPLAY"), NULL, NULL, NULL);

// Make the DC to manipulate the bitmap
HDC dcMem = ::CreateCompatibleDC( hddc);

// (200,100) 24 bit bitmap
BITMAPINFO bmi;
ZeroMemory( &bmi, sizeof(bmi));
bmi.bmiHeader.biSize = sizeof(bmi);
bmi.bmiHeader.biWidth = 200;
bmi.bmiHeader.biHeight = 100;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 24;

// pBitsDib is the pointer to the bytes in the bitmap
unsigned char *pBitsDib = 0;
hBitDib = ::CreateDIBSection( dcMem, &bmi, DIB_RGB_COLORS, (void**)(&pBitsDib), NULL, 0);

// Make the bitmap be the drawing surface for dcMem
HGDIOBJ tmpObj = ::SelectObject( dcMem, hBitDib);

// Draw something into it
Rect pos = { 0, 0, 0, 0 };
pos.right = 200;
pos.bottom = 100;
::FillRect( dcCopy, &pos, (HBRUSH) ::GetStockObject(GRAY_BRUSH));

// Finish
::SelectObject( dcMem, tmpObj);
::ReleaseDC( dcMem);

// Note DeleteObject also frees the memory for the bits (unless
// you allocated it yourself)
::DeleteObject( hBitDib);

Bitmaps

• Bitmap in Memory (DIBSection)
• Bitmap, Reading one from a file

Functions

Functions

Font and Text

Using an Object

To use an object (Bitmap, Brush, Font, Pen, Region), you must select it into a DC through this:

HGDIOBJ SelectObject( HDC, HGDIOBJ);

It returns the previous Object

Releasing