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I'm trying to write a text overlay function that generates a semitransparent background with text on it in the top right hand corner of the viewport. I wrote a test MFC application project with mostly default settings (I don't remember exactly, but AFAIK, none of the settings should cause the problems I'm seeing).
Here is the code:
void DrawSemitransparentRect(CDC& destDC, CRect rect, float percentGrayBackground, COLORREF overlayColour, float overlayPercentOpaque)
{
rect.NormalizeRect();
CDC temp_dc; // Temp dc for semitransparent text background
temp_dc.CreateCompatibleDC(&destDC);
CBitmap layer; // Layer for semitransparent text background
layer.CreateCompatibleBitmap(&destDC, 1, 1);
CBitmap* pOldBitmap = temp_dc.SelectObject(&layer);
BLENDFUNCTION blendFunction = { AC_SRC_OVER, 0, 0, 0 };
auto DrawSemitransparentRectHelper = [&](COLORREF colour, float transparency)
{
temp_dc.SetPixel(0, 0, colour);
blendFunction.SourceConstantAlpha = BYTE(transparency * 255 / 100);
// Draw semitransparent background
VERIFY(destDC.AlphaBlend(rect.left, rect.top, rect.Width(), rect.Height()
, &temp_dc, 0, 0, 1, 1, blendFunction));
};
// Lighten up the area to make more opaque without changing overlay colour.
DrawSemitransparentRectHelper(RGB(255, 255, 255), percentGrayBackground);
// Draw overlay colour
DrawSemitransparentRectHelper(overlayColour, overlayPercentOpaque);
temp_dc.SelectObject(pOldBitmap);
}
void DrawOverlayText(CDC & dc, CFont &windowFont, CRect const& windowRectDP, CString const& overlayText, CRect* pBoundingRectDP)
{
static bool debug = true;
int savedDC = dc.SaveDC();
::SetMapMode(dc.GetSafeHdc(), MM_TWIPS);
// Reset the window and viewport origins to (0, 0).
CPoint windowOrg, viewportOrg;
::SetWindowOrgEx(dc.GetSafeHdc(), 0, 0, &windowOrg);
::SetViewportOrgEx(dc.GetSafeHdc(), 0, 0, &viewportOrg);
LOGFONT logFont;// = { 12 * 10, 0, 0, 0, 100, 0, 0, 0, 0, 0, 0, 0, 255, _T("Times New Roman") };
windowFont.GetLogFont(&logFont);
logFont.lfHeight = 12 * 10; // 12 point font? Why isn't this *20? TWIPS are 20ths of a point.
// Font for the overlay text
CFont font;
font.CreatePointFontIndirect(&logFont, &dc);
CFont* pOldFont = dc.SelectObject(&font);
// window rect in Logical Points
CRect windowRect(windowRectDP);
dc.DPtoLP(windowRect);
// Get text extent in Logical Points
CRect textRect;
dc.DrawText(overlayText, textRect, DT_CALCRECT);
// inflation rectangle to add pixels around text
CRect inflate(8, 0, 8, 4);
dc.DPtoLP(&inflate);
// Create the bounding rect on the right hand of the view, making it a few pixels wider.
CRect boundingRect(textRect);
if (!debug)
{
boundingRect.InflateRect(inflate);
}
boundingRect.NormalizeRect();
boundingRect += CPoint(windowRect.Width() - boundingRect.Width(), 0);
CRect boundingRectDP(boundingRect);
if (pBoundingRectDP || !debug)
{
// Get the bounding rect in device coordinates
dc.LPtoDP(boundingRectDP);
*pBoundingRectDP = boundingRectDP;
}
if (!debug)
{
// round the bottom corners of the text box by clipping it
CRgn clip;
boundingRectDP.NormalizeRect();
clip.CreateRoundRectRgn(
boundingRectDP.left + 1 // +1 needed to make rounding coner match more closely to bottom right coner
, boundingRectDP.top - boundingRectDP.Height() // Getting rid of top rounded corners
, boundingRectDP.right
, boundingRectDP.bottom + 1
, 16, 16 // rounding corner may have to be more dynamic for different DPI screens
);
::SelectClipRgn(dc.GetSafeHdc(), (HRGN)clip.GetSafeHandle());
clip.DeleteObject();
}
// Calculatte centre position of text
CPoint centrePos(
boundingRect.left + (boundingRect.Width() - textRect.Width()) / 2 + 1
, boundingRect.top + (boundingRect.Height() - textRect.Height()) / 2 + 1);
if (debug)
{
// in debug mode, output text and then put semitransparent bounding rect over it.
dc.SetBkMode(debug ? OPAQUE : TRANSPARENT);
dc.SetBkColor(RGB(255, 0, 0));
dc.SetTextColor(RGB(0, 0, 0));
dc.TextOut(centrePos.x, centrePos.y, overlayText);
DrawSemitransparentRect(dc, boundingRect, 60, RGB(0, .25 * 255, .75 * 255), 40);
}
else
{
// 2 pixel offset in Logical Points
CPoint textShadowOffset(2, 2);
dc.DPtoLP(&textShadowOffset);
// in !debug mode, output semitransparent bounding rect and then put text over it.
DrawSemitransparentRect(dc, boundingRect, 60, RGB(0, .25 * 255, .75 * 255), 40);
dc.SetBkMode(debug ? OPAQUE : TRANSPARENT);
dc.SetTextColor(RGB(0, 0, 0));
dc.TextOut(centrePos.x, centrePos.y, overlayText);
dc.SetTextColor(RGB(255, 255, 255));
dc.TextOut(centrePos.x - textShadowOffset.x, centrePos.y - textShadowOffset.y, overlayText);
}
// Restore DC's state
dc.SelectObject(pOldFont);
dc.RestoreDC(savedDC);
}
// OnPaint() function for CView derived class.
void COverlayOnCViewView::OnPaint()
{
CPaintDC dc(this); // device context for painting
CString m_overlayText = _T("abcdefg ABCDEFG");
CFont windowFont;
LOGFONT logFont = { -12, 0, 0, 0, 400, 0, 0, 0, DEFAULT_CHARSET, 0, 0, CLEARTYPE_QUALITY, 0, _T("Segoe UI") };
windowFont.CreatePointFontIndirect(&logFont, &dc);
CRect windowRect;
GetClientRect(windowRect);
DrawOverlayText(dc, windowFont, windowRect, m_overlayText, nullptr);
}
Now, this works perfectly well in the default project, where I get the following:
But when I put it into another preexisting project, I get this:
You can see that the text is actually positioned above the translucent rectangle.
If I move the rectangle down the height of the text box, by changing
boundingRect += CPoint(windowRect.Width() - boundingRect.Width(), 0);
to
boundingRect += CPoint(windowRect.Width() - boundingRect.Width(), textRect.Height());
I get:
It's like the text function is specifying the bottom left corner rather than the top left corner for placement.
I wrote the free functions so that it should work with any DC, even if that DC has had its coordinate system manipulated, but perhaps I've forgotten to reset something?
The default project is using MFC 14.0.24212.0, but the project I tried to import this code into is using MFC 12.0.21005.1. Could that be an issue? I'm not sure how to change the default project to use the earlier version of MFC to test that.
Edit
Note that in the default project, I could have put the code into the OnDraw() function like this:
void COverlayOnCViewView::OnDraw(CDC* pDC)
{
COverlayOnCViewDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;
// TODO: add draw code for native data here
CString m_overlayText = _T("abcdefg ABCDEFG");
CFont windowFont;
LOGFONT logFont = { -12, 0, 0, 0, 400, 0, 0, 0, DEFAULT_CHARSET, 0, 0, CLEARTYPE_QUALITY, 0, _T("Segoe UI") };
windowFont.CreatePointFontIndirect(&logFont, pDC);
CRect windowRect;
GetClientRect(windowRect);
DrawOverlayText(*pDC, windowFont, windowRect, m_overlayText, nullptr);
}
The only reason why I didn't was because the application I'm putting this into doesn't have one and I wanted to mimic that project as closely as possible. If you create a default application to test this, remember either to put the ON_WM_PAINT() macro in the MESSAGE MAP or use the OnDraw() function shown instead. They both seem to have the same results in the default project.
I have to use GDI to print documents with printers in general.I can get the device no problem. I also communicate it desired page size like:
HANDLE hPrinter;
OpenPrinterW( printerName, &hPrinter, 0 );
DocumentPropertiesW( 0, hPrinter, printerName,
pDevMode, NULL, DM_OUT_BUFFER);
if( settings.paperLength > 0 && settings.paperWidth > 0 )
{
if( pDevMode->dmFields & DM_PAPERSIZE )
{
pDevMode->dmPaperSize = 0;
}
if( pDevMode->dmFields & DM_PAPERLENGTH )
{
pDevMode->dmPaperLength = settings.paperLength;
}
if( pDevMode->dmFields & DM_PAPERWIDTH )
{
pDevMode->dmPaperWidth = settings.paperWidth;
}
}
DocumentPropertiesW( 0, hPrinter, printerName, 0, pDevMode,
DM_IN_BUFFER | DM_OUT_BUFFER );
ClosePrinter( hPrinter );
Then I StretchBlt my document and print it.
DOCINFOW di;
memset ((void *) &di, 0, sizeof (di));
di.cbSize = sizeof (DOCINFOW);
di.lpszDocName = utf_to_widechar("Document").data();
HDC hdc = this->deviceContext;
auto cxpage = GetDeviceCaps( hdc, HORZRES );
auto cypage = GetDeviceCaps( hdc, VERTRES );
auto hdcMem = CreateCompatibleDC( hdc );
BITMAPINFO bi;
bi.bmiHeader = {sizeof(bi.bmiHeader), settings.width, settings.height,
1, 24, BI_RGB, 0, 0x0ec4, 0x0ec4, 0, 0};
LPVOID ppvBits;
auto hBitmap = CreateDIBSection( 0, &bi, DIB_RGB_COLORS, &ppvBits, 0, 0 );
auto hbmOld = SelectObject( hdcMem, hBitmap );
StartDocW( hdc, &di);
for(int i = 0; i < this->colorTables.size(); ++i)
{
int size = settings.width * settings.height * 3;
StartPage( hdc );
SetDIBits( 0, hBitmap, 0, settings.height,
(PVOID)&(colorTables[i][0]), &bi, DIB_RGB_COLORS );
SetMapMode( hdc, MM_ISOTROPIC )
SetWindowExtEx( hdc, cxpage, cypage, 0 );
SetViewportExtEx( hdc, cxpage, cypage, 0 );
SetViewportOrgEx( hdc, 0, 0, 0 );
StretchBlt( hdc, 0, 0, cxpage, cypage, hdcMem, 0, 0,
settings.width, settings.height, SRCCOPY );
EndPage( hdc );
}
EndDoc( hdc );
SelectObject( hdcMem, hbmOld );
DeleteDC( hdcMem );
Now, my document is 210mmx99mm. Most printers more or less properly handle this: the print size is proper, and either is it located left top corner, or top in the middle, if a printer supports smaller paper sizes. The issue is, I am working with HP printer now and it just doesn't work this way. The print is stretched all over A4 [which means that it is resized to cover whole A4 page, which is both wrong size and wrong proportions]. I know the printer can actually do it. I can use other software to print such documents properly. It just seems HP doesn't fully support some GDI functions. Is there some way to sort it out?
I am new to Win32 and trying to get a GDI based code in C++ ( for technical reasons don't want to use GDI+)
Edit: Simplied the question:
I need to draw a rectangle around the text that is drawn in the middle of the window.
- How can I populate the rectangle co-ordinates?
- Can any one help with the line - Rectangle(x1,y1,x2,y2)? - How to calculate these (x1,y1) & (x2,y2) values?
Thank you..
hdc = BeginPaint(hWnd, &ps);
GetClientRect(hWnd, &rcClient);
SelectObject(hdc, GetStockObject(DEFAULT_GUI_FONT));
SetTextColor(hdc, RGB(255, 0, 0));
DrawText(hdc, wstring(s.begin(),s.end()).c_str(), -1, &rectResult, DT_SINGLELINE | DT_CALCRECT);
DrawText(hdc, wstring(s.begin(),s.end()).c_str(), -1, &rcClient, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
// Here I need help - How to I place the rectangle around the Text - which is drawn in the middle of the window?
// It looks like need to use - rectResult.bottom/top/left/right - but don't know how..
Rectangle(hdc, 0,0,100,100);
You don't actually have to center the text yourself. The GDI text output functions can do that for you if you pass the appropriate flags.
For example, if you call DrawText and pass the DT_CENTER flag, it will automatically draw the text in the middle of the specified rectangle (horizontally centered).
Assuming you have only a single line of text (which it sounds like you do), you can get it to automatically vertically center the text by passing the DT_SINGLELINE and DT_VCENTER flags.
So all you really have to do is write code to divide your window's client area up into 4 equal parts, and then pass those rectangles to the DrawText function. That's not terribly difficult. Put a pencil and paper to it if you can't visualize it in your head.
void PaintWindow(HWND hWnd)
{
// Set up the device context for drawing.
PAINTSTRUCT ps;
HDC hDC = BeginPaint(hWnd, &ps);
HPEN hpenOld = static_cast<HPEN>(SelectObject(hDC, GetStockObject(DC_PEN)));
HBRUSH hbrushOld = static_cast<HBRUSH>(SelectObject(hDC, GetStockObject(NULL_BRUSH)));
// Calculate the dimensions of the 4 equal rectangles.
RECT rcWindow;
GetClientRect(hWnd, &rcWindow);
RECT rc1, rc2, rc3, rc4;
rc1 = rc2 = rc3 = rc4 = rcWindow;
rc1.right -= (rcWindow.right - rcWindow.left) / 2;
rc1.bottom -= (rcWindow.bottom - rcWindow.top) / 2;
rc2.left = rc1.right;
rc2.bottom = rc1.bottom;
rc3.top = rc1.bottom;
rc3.right = rc1.right;
rc4.top = rc1.bottom;
rc4.left = rc1.right;
// Optionally, deflate each of the rectangles by an arbitrary amount so that
// they don't butt up right next to each other and we can distinguish them.
InflateRect(&rc1, -5, -5);
InflateRect(&rc2, -5, -5);
InflateRect(&rc3, -5, -5);
InflateRect(&rc4, -5, -5);
// Draw (differently-colored) borders around these rectangles.
SetDCPenColor(hDC, RGB(255, 0, 0)); // red
Rectangle(hDC, rc1.left, rc1.top, rc1.right, rc1.bottom);
SetDCPenColor(hDC, RGB(0, 255, 0)); // green
Rectangle(hDC, rc2.left, rc2.top, rc2.right, rc2.bottom);
SetDCPenColor(hDC, RGB(0, 0, 255)); // blue
Rectangle(hDC, rc3.left, rc3.top, rc3.right, rc3.bottom);
SetDCPenColor(hDC, RGB(255, 128, 0)); // orange
Rectangle(hDC, rc4.left, rc4.top, rc4.right, rc4.bottom);
// Draw the text into the center of each of the rectangles.
SetBkMode(hDC, TRANSPARENT);
SetBkColor(hDC, RGB(0, 0, 0)); // black
// TODO: Optionally, set a nicer font than the default.
DrawText(hDC, TEXT("Hello World!"), -1, &rc1, DT_CENTER | DT_SINGLELINE | DT_VCENTER);
DrawText(hDC, TEXT("Hello World!"), -1, &rc2, DT_CENTER | DT_SINGLELINE | DT_VCENTER);
DrawText(hDC, TEXT("Hello World!"), -1, &rc3, DT_CENTER | DT_SINGLELINE | DT_VCENTER);
DrawText(hDC, TEXT("Hello World!"), -1, &rc4, DT_CENTER | DT_SINGLELINE | DT_VCENTER);
// Clean up after ourselves.
SelectObject(hDC, hpenOld);
SelectObject(hDC, hbrushOld);
EndPaint(hWnd, &ps);
}
RECT rect={0,0,0,0};
const char *str="Test Text";
DrawText(hDC, str, strlen(str), &rect, DT_CALCRECT | DT_NOCLIP);
Rectangle(hDC,rect.left,rect.top,rect.right,rect.bottom);
DrawText(hDC, str, strlen(str), &rect, DT_CENTER | DT_VCENTER | DT_SINGLELINE|DT_NOCLIP);
Got it finally :) Thanks a lot Cody Gray for pointing me in right direction about this :)
GetTextExtentPoint32(hDC, str, strlen(str), &sz2);
rect2.top=rect2.bottom+sz2.cy;
rect2.right=rect2.top+sz2.cx;
Rectangle(hDC,rect2.left,rect2.top,rect2.right,rect2.bottom);
DrawText(hDC, str, -1, &rect2, DT_CENTER | DT_VCENTER | DT_SINGLELINE|DT_NOCLIP);
I need to make bird animation in WS_OVERLAPPED window (as shown below). Animation is represented by 8 images:
The blue color in the image (which is RGB(0, 255, 255)) has to be transparent (see screenshot below).
I wanted to do this using CreateWindowEx() (bird would be represented by layered window) with WS_EX_LAYERED argument. Unfortunately bird must be WS_CHILD. Mixing WS_EX_LAYERED | WS_CHILD is not legal in Windows 7:
Windows 8: The WS_EX_LAYERED style is supported for top-level windows and child windows. Previous Windows versions support WS_EX_LAYERED only for top-level windows.
Final effect should look like this (I've already painted window's background - the only problem is the bird):
How can I achieve this effect? How to animate bird in parent window?
If you have any idea how to implement bird animation with transparent background color please share.
Since animation is done even when there's no interaction with the window, we'll need a timer:
case WM_CREATE:
// load resources
SetTimer(hwnd, 0, 250, NULL); // set timer to 250 ms
return 0;
...
case WM_DESTROY:
KillTimer(hwnd, 0);
// release the resources
return 0;
We can invalidate the whole window each timer tick, but it would be better to redraw only needed part. We'll also update the current frame number here:
case WM_TIMER:
frame_number++;
if (frame_number >= 8)
frame_number = 0;
RECT rc = { 30, 30, 80, 80 }; // a rectangle from (30,30) to (80,80)
InvalidateRect(hwnd, &rc, FALSE);
return 0;
Then, we draw the current frame in the WM_PAINT handler:
case WM_PAINT:
// draw the sky
SelectObject(hDCMem, hBird);
TransparentBlt(hDC, 30, 30, 50, 50, hDCMem, frame_number * 51, 0, 50, 50, RGB(0, 255, 255)); // 51 is 50 (side of a bird frame) + 1 (gap between the frames)
// draw the rest
return 0;
I've finally find out how to do it. It's quite tricky.
The full description of the solution is available here - winprog.org/tutorial/transparency.html. For polish readers here is great translation.
Simple idea in brief:
Giving bitmaps the appearance of having transparent sections is quite simple, and involves the use of a black and white Mask image in addition to the colour image that we want to look transparent.
The following conditions need to be met for the effect to work correctly: First off, the colour image must be black in all areas that we want to display as transparent. And second, the mask image must be white in the areas we want transparent, and black elsewhere. The colour and mask images are displayed as the two left most images in the example picture on this page.
Simple solution in brief:
#define TRANSPARENCY_COLOR RGB(0, 255, 255)
birdBmp = (HBITMAP) LoadBitmap(hInstance, MAKEINTRESOURCE(IDB_BITMAP1));
hbmpMask = CreateBitmapMask(birdBmp, TRANSPARENCY_COLOR);
Painting:
case WM_PAINT:
{
hdc = BeginPaint(hWnd, &ps);
HDC birdMaskHdc = CreateCompatibleDC(hdc);
BITMAP bmInfo;
GetObject(birdBmp, sizeof(bmInfo), &bmInfo);
HBITMAP hbmpOld = (HBITMAP) SelectObject(birdMaskHdc, hbmpMask);
BitBlt(hdc, 0, 0, bmInfo.bmWidth, bmInfo.bmHeight, birdMaskHdc, 0, 0, SRCAND);
SelectObject(birdMaskHdc, birdBmp);
BitBlt(hdc, 0, 0, bmInfo.bmWidth, bmInfo.bmHeight, birdMaskHdc, 0, 0, SRCPAINT);
SelectObject(birdMaskHdc, hbmpOld);
DeleteDC(birdMaskHdc);
EndPaint(hWnd, &ps);
break;
}
Cleaning:
case WM_DESTROY:
{
DeleteObject(hbmpMask);
DeleteObject(birdBmp);
PostQuitMessage(0);
break;
}
Function which is responsible for creating bitmap mask:
HBITMAP CreateBitmapMask(HBITMAP hbmColour, COLORREF crTransparent)
{
HDC hdcMem, hdcMem2;
HBITMAP hbmMask, hbmOld, hbmOld2;
BITMAP bm;
GetObject( hbmColour, sizeof( BITMAP ), & bm );
hbmMask = CreateBitmap( bm.bmWidth, bm.bmHeight, 1, 1, NULL );
hdcMem = CreateCompatibleDC( NULL );
hdcMem2 = CreateCompatibleDC( NULL );
hbmOld =( HBITMAP ) SelectObject( hdcMem, hbmColour );
hbmOld2 =( HBITMAP ) SelectObject( hdcMem2, hbmMask );
SetBkColor( hdcMem, crTransparent );
BitBlt( hdcMem2, 0, 0, bm.bmWidth, bm.bmHeight, hdcMem, 0, 0, SRCCOPY );
BitBlt( hdcMem, 0, 0, bm.bmWidth, bm.bmHeight, hdcMem2, 0, 0, SRCINVERT );
SelectObject( hdcMem, hbmOld );
SelectObject( hdcMem2, hbmOld2 );
DeleteDC( hdcMem );
DeleteDC( hdcMem2 );
return hbmMask;
}
I'm on Windows 7, and i am trying to display an icon with transparency on my contextual menu but it doesn't work.
I am trying to use LoadImage like this :
m_hMenuBmp = (HBITMAP)::LoadImage(g_hInst, L"C:\\Users\\nicolas\\AppData\\Roaming\\MyApp\\icon.bmp", IMAGE_BITMAP, 16, 16, LR_LOADFROMFILE | LR_LOADTRANSPARENT );
and my icon.bmp is set to 256 colors with white ( 255, 255, 255 ) on background ...
I don't know why this isn't working ...
I tried the ARGB Method of Raymon Chen but it didn't work neither !
int cx = GetSystemMetrics(SM_CXSMICON);
int cy = GetSystemMetrics(SM_CYSMICON);
BITMAPINFO bmi = {0};
bmi.bmiHeader.biSize =sizeof(bmi.bmiHeader);
bmi.bmiHeader.biWidth = cx;
bmi.bmiHeader.biHeight = cy;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = BI_RGB;
DWORD *pBits;
m_hMenuBmp = CreateDIBSection(NULL, &bmi, DIB_RGB_COLORS, (void **)&pBits, NULL , 0);
if (m_hMenuBmp)
{
for (int y = 0; y < cy ; y++ )
{
for (int x = 0; x < cx; x++)
{
BYTE bAlpha = x * x * 255 / cx / cx;
DWORD dv = (bAlpha << 24) | (bAlpha << 16) | bAlpha ;
pBits[y *cx + x] - dv;
}
}
}
And I don't know why ... my icon isn't displayed with this method ..
I found a way to did this easily :
HICON hIcon = (HICON)LoadImage( NULL, L"icon.ico", IMAGE_ICON, 16, 16, LR_LOADFROMFILE );
HDC hDC = ::GetDC( NULL );
m_hMenuBmp = ::CreateCompatibleBitmap( hDC, 16, 16 );
HDC hDCTemp = ::CreateCompatibleDC( hDC );
::ReleaseDC( NULL, hDC );
HBITMAP hBitmapOld = ( HBITMAP ) ::SelectObject( hDCTemp, m_hMenuBmp );
::DrawIconEx( hDCTemp, 0, 0, hIcon, 16, 16, 0, ::GetSysColorBrush( COLOR_MENU ), DI_NORMAL );
::SelectObject( hDCTemp, hBitmapOld );
::DeleteDC( hDCTemp );
I was able to get this to work:
HBITMAP hBitmap = (HBITMAP)::LoadImage(NULL, "C:\\moo\\res\\bitmap1.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE | LR_LOADTRANSPARENT | LR_LOADMAP3DCOLORS);
m_pic.SetBitmap(hBitmap);
The trick was LR_LOADMAP3DCOLORS together with LR_LOADTRANSPARENT. This was for a dialog box, by the way. Without LR_LOADMAP3DCOLORS, my white background stayed white.