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POGDI+ Font Rendering, especially in layered windows
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copied!<p>This my friends, is a going to be long one...</p> <p>I am getting some quite bizarre behaviour when I try to render text in a layered window.</p> <p>The strange thing is that for some combinations of font/font-style/font-size, GDI+ changes the rendering method. For Tahoma-Bold fonts sizes <em>between</em> 8.49 and 16.49 (Pixel-Units) inclusive "fail". For other fonts and styles I get "fails" at different sizes.</p> <p><img src="https://i.stack.imgur.com/lFvX4.png" alt="output from code below"></p> <p><strong>For clarity I have provided a complete executable example further down.</strong> The two key parameters to play with are on line 23:</p> <pre><code>Color g_oTextColor( 255, 240, 0, 0 ); // Simply change Color to ( 254, 240, 0, 0 ) [to add slight transparency] and everything will work! #define USE_LAYERED_WINDOW // or just comment this line out [to use a regular window], and everything will work! </code></pre> <hr> <p>When using layered windows and full opacity the fonts draw a transparent "hole" in the background. However if I add a slight transparency to the text colour (alpha-channel = 254) the fonts become opaque. Or if I use regular (non-layered) windows the fonts render opaque. <strong>What is going on here??</strong></p> <p>But even without the layered/transparency problems it is clear that something strange is happening here. The fonts size 8.49 - 16.48 get rendered pixel perfect, the other fonts have slight blurry quality, especially the small ones. So it seems that the system takes a different approach to rendering these medium sizes. <strong>Can somebody shed some light on this, how can I possibly render for example fonts size 8.0 pixels without the blurriness above?</strong> I have tried all sorts of settings for <code>SetTextRenderingHint()</code> and <code>SetTextContrast()</code> but none looked crisp for fonts of size 8. I have tried Tahoma & Arial only...</p> <hr> <p><strong>Side question 1:</strong> I wanted to use pure GDI+ for the off-screen drawing but I could not get it work by simply creating <code>Bitmap</code> & <code>Graphics</code> objects. I still had to use old GDI stuff to create a DC and to select the HBitmap into it. How can I do it all in GDI+?</p> <p><strong>Side question 2 (Geeks only):</strong> I also tried to draw the fonts in good-old GDI but there I got some even more bizarre effects: <strong>(1)</strong> In a layered window the text became transparent but in an <em>additive</em> way. (So a red text would look fine if the window behind was dark but if the window behind it was whit the text disappeared completely!) Furthermore if I filled my own window with a semi-transparent square, then that behave as expected. (A red square would turn dark red if the window behind it was black, and the square would turn light red over a white window). And I can observe both these behaviours simultaneously in one layered window. And <strong>(2)</strong> as a highly undesired bonus the drawn text lost it's hit-test and became un-clickable? <strong>Any explanations out there?</strong> </p> <p>And if you have read this far, thanks for enduring, and thanks for any answers!</p> <pre><code>// Create as a console application project // + Unicode charset // + Precompiled headers off // + make sure to add linker input: gdiplus.lib #ifndef _WIN32_WINNT // Allow use of features specific to Windows XP or later. #define _WIN32_WINNT 0x0501 // Change this to the appropriate value to target other versions of Windows. #endif // Standard and GDI+ stuffstuff #include <stdio.h> #include <tchar.h> #include <windows.h> #include <iostream> #include <cassert> #include <Gdiplus.h> using namespace Gdiplus; GdiplusStartupInput g_oGdiPlusStartupInput; ULONG_PTR g_pGdiPlusToken = NULL; // #*#*#*#*#*#*#*#*# LINES TO CHANGE ---------->---------->----------> Color g_oTextColor( 255, 240, 0, 0 ); // Simply change Color to ( 254, 240, 0, 0 ) [to add slight transparency] and everything will work! #define USE_LAYERED_WINDOW // or just comment this line out [to use a regular window], and everything will work! // Forward declarations void RegWndClass(); LRESULT CALLBACK WndProc( HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam ); void CreateWindows(); void Draw(); void MsgLoop(); // Other Globals ATOM g_iWndClass = 0; HWND g_hWndGdiPlus = NULL; HWND g_hWndGdi = NULL; const wchar_t* g_pWndClass = L"TST"; int g_iWidth = 200; int g_iHeight = 200; // Main entry-point int _tmain( int argc, _TCHAR* argv[] ) { GdiplusStartup( &g_pGdiPlusToken, &g_oGdiPlusStartupInput, NULL ); RegWndClass(); CreateWindows(); Draw(); MsgLoop(); ::UnregisterClass( g_pWndClass, NULL ); ::Sleep( 500 ); GdiplusShutdown( g_pGdiPlusToken ); return 0; } // _tmain void CreateWindows() { #ifdef USE_LAYERED_WINDOW // The key trick is to create a window with style WS_EX_LAYERED, but WITHOUT any subsequent calls to SetLayeredWindowAttributes() // This gives us a magic window that must be updated with UpdateLayeredWindow() ( and it does NOT recieve any WM_PAINT messages ) // as brilliantly described in: http://alexkr.com/source-code/50/layered-windows-and-updatelayeredwindow/ g_hWndGdiPlus = ::CreateWindowEx( WS_EX_LAYERED, g_pWndClass, L"", WS_POPUP | WS_VISIBLE, 1000, 200, g_iWidth, g_iHeight, NULL, NULL, NULL, NULL ); #else g_hWndGdiPlus = ::CreateWindowEx( 0, g_pWndClass, L"", WS_OVERLAPPEDWINDOW | WS_POPUP | WS_VISIBLE, 1000, 200, g_iWidth, g_iHeight, NULL, NULL, NULL, NULL ); #endif //g_hWndGdi = ::CreateWindowEx( WS_EX_LAYERED, g_pWndClass, L"", WS_POPUP | WS_VISIBLE, 720, 500, 200, 200, NULL, NULL, NULL, NULL ); } // CreateWindows void Draw() { // Init GDI+ surface HDC hOff = ::CreateCompatibleDC( NULL ); Bitmap oDaBigOne( g_iWidth, g_iHeight, PixelFormat32bppARGB ); HBITMAP hBMit = NULL; Color oCol( 0, 0, 0, 0 ); oDaBigOne.GetHBITMAP( oCol, &hBMit ); HGDIOBJ hSave = ::SelectObject( hOff, hBMit ); #ifdef USE_LAYERED_WINDOW Graphics oGraph( hOff ); #else Graphics oGraph( g_hWndGdiPlus ); #endif oGraph.Clear( Color( 255, 55, 155, 255 ) ); // Draw text oGraph.SetTextRenderingHint( TextRenderingHintAntiAliasGridFit ); oGraph.SetTextContrast( 0xffffffff ); oGraph.SetCompositingMode( CompositingModeSourceOver ); oGraph.SetCompositingQuality( CompositingQualityHighQuality ); oGraph.SetPixelOffsetMode( PixelOffsetModeHighQuality ); const FontFamily oFamily( L"Tahoma", NULL ); #if 1 // Use bold Font oF600( &oFamily, 6.00, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF800( &oFamily, 8.00, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF848( &oFamily, 8.48, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF849( &oFamily, 8.49, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1200( &oFamily, 12.00, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1500( &oFamily, 15.00, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1648( &oFamily, 16.48, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1649( &oFamily, 16.49, FontStyle::FontStyleBold, Unit::UnitPixel ); #else // Use regular Font oF600( &oFamily, 6.00, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF800( &oFamily, 8.00, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF848( &oFamily, 8.48, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF849( &oFamily, 8.49, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1200( &oFamily, 12.00, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1500( &oFamily, 15.00, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1648( &oFamily, 16.48, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1649( &oFamily, 16.49, FontStyle::FontStyleRegular, Unit::UnitPixel ); #endif assert( oF600.GetLastStatus() == Ok ); // Make sure font is OK SolidBrush oBrush( g_oTextColor ); double dy = 1.0; oGraph.DrawString( L"Size 6.00", -1, &oF600, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 8.00", -1, &oF800, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 8.48", -1, &oF848, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 8.49", -1, &oF849, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 12.00", -1, &oF1200, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 15.00", -1, &oF1500, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 16.48", -1, &oF1648, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 16.49", -1, &oF1649, PointF( 30.0, dy += 18.0 ), &oBrush ); #ifndef USE_LAYERED_WINDOW return; #endif // Do da layered window magic stuff BLENDFUNCTION oBF = { 0 }; oBF.BlendOp = AC_SRC_OVER; oBF.BlendFlags = 0; oBF.SourceConstantAlpha = 255; oBF.AlphaFormat = AC_SRC_ALPHA; SIZE oSize = { 0 }; oSize.cx = g_iWidth; oSize.cy = g_iHeight; POINT oPTZero = { 0 }; RECT oRect = { 0 }; ::GetWindowRect( g_hWndGdiPlus, &oRect ); POINT oPTWnd = { 0 }; oPTWnd.x = oRect.left; oPTWnd.y = oRect.top; //HDC hDC = oGraph.GetHDC(); BOOL bOK = ::UpdateLayeredWindow( g_hWndGdiPlus, NULL, //HDC hdcDst, &oPTWnd, // POINT &oPtNull, &oSize, // SIZE *psize, hOff, // HDC hdcSrc, &oPTZero, // POINT *pptSrc, RGB(255,255,255), // COLORREF crKey, &oBF, // BLENDFUNCTION *pblend, ULW_ALPHA // DWORD dwFlags ); } // Draw void MsgLoop() { ::SetTimer( g_hWndGdiPlus, 0, 19999, NULL ); // Self-destruct timer MSG msg = { 0 }; while ( ::GetMessage( &msg, NULL, 0, 0 ) ) { ::TranslateMessage(&msg); ::DispatchMessage(&msg); } } // MsgLoop void RegWndClass() { WNDCLASSEX wcex = { 0 }; wcex.cbSize = sizeof(WNDCLASSEX); wcex.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC; wcex.lpfnWndProc = WndProc; wcex.cbClsExtra = 0; wcex.cbWndExtra = 8; // 8 bytes, to allow for 64-bit architecture wcex.hInstance = NULL; // CHECK wcex.hIcon = NULL; wcex.hCursor = ::LoadCursor(NULL, IDC_ARROW); wcex.hbrBackground = (HBRUSH)NULL_BRUSH; // CHECK wcex.lpszMenuName = NULL; wcex.lpszClassName = g_pWndClass; wcex.hIconSm = NULL; g_iWndClass = ::RegisterClassEx(&wcex); } // RegWndClass LRESULT CALLBACK WndProc( HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam ) { switch( uiMsg ) { case WM_TIMER: { std::wstring s; std::wcout << L"Let´s quit" ; ::PostQuitMessage( 0 ); return 0; } case WM_PAINT: Draw(); break; default: { return DefWindowProc( hWnd, uiMsg, wParam, lParam ); } } return DefWindowProc( hWnd, uiMsg, wParam, lParam ); } // WndProc </code></pre> <p><strong>[EDIT] Problem solved! Code below according to <a href="https://stackoverflow.com/users/865874/rodrigo">Rodrogo´s</a> excellent suggestions. Kudos and an immense amount of thanks to him. I am really grateful.</strong></p> <p>All edits are marked with //#MOD</p> <pre><code>// Create as a console application project // + Unicode charset // + Precompiled headers off // + make sure to add linker input: gdiplus.lib #ifndef _WIN32_WINNT // Allow use of features specific to Windows XP or later. #define _WIN32_WINNT 0x0501 // Change this to the appropriate value to target other versions of Windows. #endif // Standard stuff #include <stdio.h> #include <tchar.h> #include <windows.h> #include <iostream> #include <cassert> // GDI+ stuff #include <Gdiplus.h> using namespace Gdiplus; GdiplusStartupInput g_oGdiPlusStartupInput; ULONG_PTR g_pGdiPlusToken = NULL; // #*#*#*#*#*#*#*#*# LINES TO CHANGE ---------->---------->----------> Color g_oTextColor( 255, 240, 0, 0 ); // Simply change Color to ( 254, 240, 0, 0 ) [to add slight transparency] and everything will work! #define USE_LAYERED_WINDOW // or just omment this line [to use a regular window], and everything will work! // Forward declarations void RegWndClass(); LRESULT CALLBACK WndProc( HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam ); void CreateWindows(); void Draw(); void MsgLoop(); // Other Globals ATOM g_iWndClass = 0; HWND g_hWndGdiPlus = NULL; HWND g_hWndGdi = NULL; const wchar_t* g_pWndClass = L"TST"; int g_iWidth = 200; int g_iHeight = 200; // Main entry-point int _tmain( int argc, _TCHAR* argv[] ) { GdiplusStartup( &g_pGdiPlusToken, &g_oGdiPlusStartupInput, NULL ); RegWndClass(); CreateWindows(); Draw(); MsgLoop(); ::UnregisterClass( g_pWndClass, NULL ); ::Sleep( 500 ); GdiplusShutdown( g_pGdiPlusToken ); return 0; } // _tmain void CreateWindows() { #ifdef USE_LAYERED_WINDOW // The key trick is to create a window with style WS_EX_LAYERED, but WITHOUT any subsequent calls to SetLayeredWindowAttributes() // This gives us a magic window that must be updated with UpdateLayeredWindow() ( and it does NOT recieve any WM_PAINT messages ) // as brilliantly described in: http://alexkr.com/source-code/50/layered-windows-and-updatelayeredwindow/ g_hWndGdiPlus = ::CreateWindowEx( WS_EX_LAYERED, g_pWndClass, L"", WS_POPUP | WS_VISIBLE, 1000, 200, g_iWidth, g_iHeight, NULL, NULL, NULL, NULL ); #else g_hWndGdiPlus = ::CreateWindowEx( 0, g_pWndClass, L"", WS_OVERLAPPEDWINDOW | WS_POPUP | WS_VISIBLE, 1000, 200, g_iWidth, g_iHeight, NULL, NULL, NULL, NULL ); #endif //g_hWndGdi = ::CreateWindowEx( WS_EX_LAYERED, g_pWndClass, L"", WS_POPUP | WS_VISIBLE, 720, 500, 200, 200, NULL, NULL, NULL, NULL ); } // CreateWindows void Draw() { // Init GDI+ surface HDC hOff = ::CreateCompatibleDC( NULL ); Bitmap oDaBigOne( g_iWidth, g_iHeight, PixelFormat32bppARGB ); HBITMAP hBMit = NULL; Color oCol( 0, 0, 0, 0 ); // oDaBigOne.GetHBITMAP( oCol, &hBMit ); //#MOD // HGDIOBJ hSave = ::SelectObject( hOff, hBMit ); //#MOD { // Limit oGraph scope //#MOD #ifdef USE_LAYERED_WINDOW //Graphics oGraph( hOff ); //#MOD Graphics oGraph( &oDaBigOne ); //#MOD #else Graphics oGraph( g_hWndGdiPlus ); #endif oGraph.Clear( Color( 255, 55, 155, 255 ) ); // Draw text oGraph.SetTextRenderingHint( TextRenderingHintAntiAliasGridFit ); oGraph.SetCompositingMode( CompositingModeSourceOver ); oGraph.SetCompositingQuality( CompositingQualityHighQuality ); oGraph.SetPixelOffsetMode( PixelOffsetModeHighQuality ); const FontFamily oFamily( L"Tahoma", NULL ); #if 1 // Use bold Font oF600( &oFamily, 6.00, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF848( &oFamily, 8.48, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF849( &oFamily, 8.49, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1200( &oFamily, 12.00, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1500( &oFamily, 15.00, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1648( &oFamily, 16.48, FontStyle::FontStyleBold, Unit::UnitPixel ); Font oF1649( &oFamily, 16.49, FontStyle::FontStyleBold, Unit::UnitPixel ); #else // Use regular Font oF600( &oFamily, 6.00, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF848( &oFamily, 8.48, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF849( &oFamily, 8.49, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1200( &oFamily, 12.00, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1500( &oFamily, 15.00, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1648( &oFamily, 16.48, FontStyle::FontStyleRegular, Unit::UnitPixel ); Font oF1649( &oFamily, 16.49, FontStyle::FontStyleRegular, Unit::UnitPixel ); #endif assert( oF600.GetLastStatus() == Ok ); // Make sure font is OK SolidBrush oBrush( g_oTextColor ); double dy = 10.0; oGraph.DrawString( L"Size 6.00", -1, &oF600, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 8.48", -1, &oF848, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 8.49", -1, &oF849, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 12.00", -1, &oF1200, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 15.00", -1, &oF1500, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 16.48", -1, &oF1648, PointF( 30.0, dy += 18.0 ), &oBrush ); oGraph.DrawString( L"Size 16.49", -1, &oF1649, PointF( 30.0, dy += 18.0 ), &oBrush ); #ifndef USE_LAYERED_WINDOW return; #endif } // Limit oGraph scope //#MOD // Do da layered window magic stuff BLENDFUNCTION oBF = { 0 }; oBF.BlendOp = AC_SRC_OVER; oBF.BlendFlags = 0; oBF.SourceConstantAlpha = 255; oBF.AlphaFormat = AC_SRC_ALPHA; SIZE oSize = { 0 }; oSize.cx = g_iWidth; oSize.cy = g_iHeight; POINT oPTZero = { 0 }; RECT oRect = { 0 }; ::GetWindowRect( g_hWndGdiPlus, &oRect ); POINT oPTWnd = { 0 }; oPTWnd.x = oRect.left; oPTWnd.y = oRect.top; oDaBigOne.GetHBITMAP( oCol, &hBMit ); //#MOD HGDIOBJ hSave = ::SelectObject( hOff, hBMit ); //#MOD //HDC hDC = oGraph.GetHDC(); BOOL bOK = ::UpdateLayeredWindow( g_hWndGdiPlus, NULL, //HDC hdcDst, &oPTWnd, // POINT &oPtNull, &oSize, // SIZE *psize, hOff, // HDC hdcSrc, &oPTZero, // POINT *pptSrc, RGB(255,255,255), // COLORREF crKey, &oBF, // BLENDFUNCTION *pblend, ULW_ALPHA // DWORD dwFlags ); } // Draw void MsgLoop() { ::SetTimer( g_hWndGdiPlus, 0, 19999, NULL ); // Self-destruct timer MSG msg = { 0 }; while ( ::GetMessage( &msg, NULL, 0, 0 ) ) { ::TranslateMessage(&msg); ::DispatchMessage(&msg); } } // MsgLoop void RegWndClass() { WNDCLASSEX wcex = { 0 }; wcex.cbSize = sizeof(WNDCLASSEX); wcex.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC; wcex.lpfnWndProc = WndProc; wcex.cbClsExtra = 0; wcex.cbWndExtra = 8; // 8 bytes, to allow for 64-bit architecture wcex.hInstance = NULL; // CHECK wcex.hIcon = NULL; wcex.hCursor = ::LoadCursor(NULL, IDC_ARROW); wcex.hbrBackground = (HBRUSH)NULL_BRUSH; // CHECK wcex.lpszMenuName = NULL; wcex.lpszClassName = g_pWndClass; wcex.hIconSm = NULL; g_iWndClass = ::RegisterClassEx(&wcex); } // RegWndClass LRESULT CALLBACK WndProc( HWND hWnd, UINT uiMsg, WPARAM wParam, LPARAM lParam ) { switch( uiMsg ) { case WM_TIMER: { std::wstring s; std::wcout << L"Let´s quit" ; ::PostQuitMessage( 0 ); return 0; } case WM_PAINT: Draw(); break; default: { return DefWindowProc( hWnd, uiMsg, wParam, lParam ); } } return DefWindowProc( hWnd, uiMsg, wParam, lParam ); } // WndProc </code></pre>

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