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how to flip a HBITMAP horizontally?As an option, I thought to get an array of colors from BITMAP and write them to another BITMAP, but somehow it's too busy. Are there built-in functions or other options to do this?
You can use StretchBlt with a negative dimension as below:
HBITMAP FlipBitmapHorizontally(HBITMAP hbm) {
BITMAP bm;
GetObject(hbm, sizeof(BITMAP), &bm);
int wd = bm.bmWidth;
int hgt = bm.bmHeight;
HDC hdcScr = GetDC(NULL);
HDC hdcFlipped = CreateCompatibleDC(hdcScr);
HBITMAP hbmFlipped = CreateCompatibleBitmap(hdcScr, wd, hgt);
HGDIOBJ oldFlipped = SelectObject(hdcFlipped, hbmFlipped);
HDC hdcSrc = CreateCompatibleDC(hdcScr);
HGDIOBJ oldSrc = SelectObject(hdcSrc, hbm);
StretchBlt(hdcFlipped, wd, 0, -wd, hgt, hdcSrc, 0, 0, wd, hgt, SRCCOPY);
SelectObject(hdcSrc, oldSrc);
DeleteDC(hdcSrc);
SelectObject(hdcFlipped, oldFlipped);
DeleteDC(hdcFlipped);
ReleaseDC(NULL, hdcScr);
return hbmFlipped;
}
I got stuck with a problem - I need to create a bitmap in memory, draw some text i it and save it as a BMP file and then print out the bitmap with physical printer. I can do this drawing in the dialog window context - it works fine. But when I try to do the same drawing in printer context the text doesn't appear. I really can't figure out why it is so. Please, help me guys. Thanks in advance. Here is the code:
void CMy2Dlg::OnButton1()
{
// TODO: Add your control notification handler code here
CPrintDialog pd(false);
if (pd.DoModal()==IDOK)
{
CDC PrintDC;
HDC hdc = pd.CreatePrinterDC();
PrintDC.Attach(hdc);
DOCINFO infStru;
::ZeroMemory (&infStru, sizeof (DOCINFO));
CString title="Print test";
infStru.cbSize = sizeof (DOCINFO);
infStru.lpszDocName=title;
infStru.lpszOutput=NULL;
PrintDC.StartDoc(&infStru);
PrintDC.StartPage();
{
CRect r, r2;
CBitmap memBMP, * pOldBitmap;
CPaintDC dc(this);
CDC memDC, *pDC = &memDC;
CFont font, * pOldFont;
int width = 2000;
int height = 1500;
int textwidth = 300;
int textheight = 150;
int oldMapMode = 0;
int oldbkmode = 0;
int i, j;
LOGFONT logFont, lf;
COLORREF oldTextColor;
memset(&logFont, 0, sizeof(logFont));
logFont.lfHeight = 16;
logFont.lfWidth = 0;
logFont.lfEscapement = 0;
logFont.lfOrientation = 0;
logFont.lfWeight = FW_NORMAL;
logFont.lfItalic = FALSE;
logFont.lfUnderline = FALSE;
logFont.lfStrikeOut = 0;
logFont.lfCharSet = ANSI_CHARSET;
logFont.lfOutPrecision = OUT_DEFAULT_PRECIS;
logFont.lfClipPrecision = CLIP_DEFAULT_PRECIS;
logFont.lfQuality = DEFAULT_QUALITY;
logFont.lfPitchAndFamily = DEFAULT_PITCH | FF_SWISS;
strcpy(logFont.lfFaceName, "Arial");
if(memDC.CreateCompatibleDC(&PrintDC)) {
if (memBMP.CreateCompatibleBitmap(&PrintDC, width, height)) {
pOldBitmap = pDC->SelectObject(&memBMP);
pDC->FillSolidRect(0, 0, width, height, RGB(200, 200, 200));
oldTextColor = pDC->SetTextColor(RGB(255,0,0));
oldMapMode = pDC->SetMapMode(MM_LOMETRIC);
oldbkmode = pDC->SetBkMode(TRANSPARENT);
lf = logFont;
lf.lfHeight = -MulDiv(lf.lfHeight, GetDeviceCaps(pDC->GetSafeHdc(), LOGPIXELSY), 72);
//lf.lfHeight = 100;
font.CreateFontIndirect(&lf);
pOldFont = pDC->SelectObject(&font);
r.left = 10;
r.top = 10;
r.right = r.left + textwidth;
r.bottom = r.top + textheight;
r.top *= -1;
r.bottom *= -1;
pDC->MoveTo(r.left, r.top);
pDC->LineTo(r.right, r.top);
pDC->LineTo(r.right, r.bottom);
pDC->LineTo(r.left, r.bottom);
pDC->LineTo(r.left, r.top);
pDC->DrawText("qwerty", &r, DT_CENTER | DT_SINGLELINE | DT_VCENTER);
pDC->SetMapMode(oldMapMode);
pDC->SetTextColor(oldTextColor);
pDC->SetBkMode(oldbkmode);
PrintDC.BitBlt(10, 10, width, height, pDC, 0, 0, SRCCOPY);
pDC->SelectObject(pOldBitmap);
pDC->SelectObject(pOldFont);
font.DeleteObject();
memBMP.DeleteObject();
pDC->DeleteDC();
}
}
}
PrintDC.EndPage();
PrintDC.EndDoc();
PrintDC.Detach();
DeleteDC(hdc);
}
}
If SetMapMode(MM_LOMETRIC) is used on memory DC, then memory DC has to be drawn upside down when using BitBlt to copy to printer/display DC. The width/height will have to be adjusted as well. Just use the default map mode (MM_TEXT). Use SetMapMode(MM_LOMETRIC) when you are drawing on printer DC and you want that specific measurement units.
void CMy2Dlg::OnButton1()
{
//create the bitmap
int w = 600, h = 400;
CClientDC dc(this);
CBitmap bmp;
CDC memdc;
memdc.CreateCompatibleDC(&dc);
bmp.CreateCompatibleBitmap(&dc, w, h);
auto oldbmp = memdc.SelectObject(bmp);
//draw on bitmap
memdc.FillSolidRect(0, 0, w, h, RGB(200, 200, 200));
memdc.SetTextColor(RGB(255, 0, 0));
CRect rc(0, 0, w, h);
memdc.DrawText(L"qwerty", &rc, 0);
dc.BitBlt(0, 0, w, h, &memdc, 0, 0, SRCCOPY);//optional: draw the bitmap on dialog
CPrintDialog pd(false);
if(pd.DoModal() == IDOK)
{
CDC PrintDC;
HDC hdc = pd.GetPrinterDC();
PrintDC.Attach(hdc);
DOCINFO docinfo = { sizeof(docinfo) };
docinfo.lpszDocName = L"Print test";
PrintDC.StartDoc(&docinfo);
PrintDC.StartPage();
PrintDC.BitBlt(0, 0, w, h, &memdc, 0, 0, SRCCOPY);
PrintDC.EndPage();
PrintDC.EndDoc();
}
dc.SelectObject(oldbmp);
}
I am trying to get HBIPMAP working by reusing the HBITMAP and the HDC for performance reasons.
This is a small test project I wanted to do to learn more about CPU based Rasterization. For the window, im using SDL2.
The below code works if we comment out:
DeleteDC(hdcMem);
hdcMem = CreateCompatibleDC(device);
I can not find any example in the year 2018+.
mBackBuffer is just a Vector(DWORD)
void Device::createDeviceFromHWND(const HWND& hwnd, const int& width, const int& height)
{
// This is hacked code for an example.
auto device = GetDC(hwnd);
DWORD colorSize = 4; // ARGB;
// Create page section
// https://learn.microsoft.com/en-us/windows/desktop/memory/creating-named-shared-memory
HANDLE hMapFile;
LPCTSTR pBuf;
// https://learn.microsoft.com/en-us/windows/desktop/api/winbase/nf-winbase-createfilemappinga
hMapFile = CreateFileMappingA
(
INVALID_HANDLE_VALUE,
NULL,
PAGE_READWRITE,
0,
width * height * colorSize,
NULL
);
if (hMapFile == NULL)
{
return;
}
DWORD* buffer = (DWORD*)MapViewOfFile(
hMapFile,
FILE_MAP_ALL_ACCESS,
0,
0,
width * height * colorSize
);
BITMAPINFOHEADER header;
memset(&header, 0, sizeof(BITMAPINFOHEADER));
// https://msdn.microsoft.com/en-us/02f8ed65-8fed-4dda-9b94-7343a0cfa8c1
header.biSize = sizeof(BITMAPINFOHEADER);
header.biWidth = width;
header.biHeight = height;
header.biPlanes = 1;
header.biBitCount = 32;
header.biCompression = BI_RGB;
header.biSizeImage = width * height * sizeof(BYTE);
header.biXPelsPerMeter = 0;
header.biYPelsPerMeter = 0;
header.biClrUsed = 0;
header.biClrImportant = 0;
tagBITMAPINFO bitmap;
memset(&bitmap, 0, sizeof(tagBITMAPINFO));
// https://learn.microsoft.com/en-us/windows/desktop/api/wingdi/ns-wingdi-tagbitmapinfo
tagRGBQUAD RGBQUAD;
memset(&RGBQUAD, 0, sizeof(tagRGBQUAD));
bitmap.bmiHeader = header;
bitmap.bmiColors[0] = RGBQUAD;
LPVOID p;
// https://learn.microsoft.com/en-us/windows/desktop/api/wingdi/nf-wingdi-createdibsection
auto hBitMap = CreateDIBSection
(
device,
&bitmap,
DIB_RGB_COLORS,
&p,
hMapFile,
0
);
for (DWORD i = 0; i < width * height; ++i)
{
buffer[i] = 0xFF0000;
}
HDC hdcMem = CreateCompatibleDC(device);
auto oldHBITMAP = (HBITMAP)SelectObject(hdcMem, hBitMap);
BitBlt(
device,
0,
0,
width,
height,
hdcMem,
0,
0,
SRCCOPY
);
DeleteDC(hdcMem);
for (DWORD i = 0; i < width * height; ++i)
{
buffer[i] = 0;
}
hdcMem = CreateCompatibleDC(device);
BitBlt(
device,
400,
300,
width,
height,
hdcMem,
0,
0,
SRCCOPY
);
}
The output is a red screen, but you should see the black section in corner right.
There are several issues here, some not related to bitmap.
The handle from GetDC should be cleaned up by ReleaseDC when the handle is no longer needed.
The handle from CreateFileMapping should be cleaned up by CloseHandle, and MapViewOfFile should be cleaned up by UnmapViewOfFile.
HBITMAP handle must be cleaned up by DeleteObject
It is recommend to cleanup after SelectObject by calling SelectOject(hMemDC, oldHBitmap)
If you don't restore the old bitmap, and try to delete hMemDC, Windows cannot fulfill the request because there is another bitmap selected in device context. Windows will try to fix this error but it may fail if the code is too convoluted.
Note that Windows gives you a limit of 10,000 GDI handles. The application will crash very quickly if you don't manage these handles properly. Refer to WinAPI documentation for these functions. If in doubt, use the task manager to monitor "GDI handles" for your program.
The code should work as expected once you fix these problems, see the example below.
This of course is for demonstration only. In real world application you probably want to save the HBITMAP in the heap, instead of stack, as well as some other values. You want to minimize repeated creating these handles.
As noted in other answers and comments, painting should be done in response to WM_PAINT, where you get HDC from BeginPaint (and cleanup with EndPaint). Therefore you should avoid GetDC/ReleaseDC
void Device::createDeviceFromHWND(const HWND& hwnd, const int& width, const int& height)
{
auto hdc = GetDC(hwnd);
auto hMapFile = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, 0,
width * height * sizeof(DWORD), NULL);
auto buffer = (DWORD*)MapViewOfFile(hMapFile, FILE_MAP_ALL_ACCESS, 0, 0,
width * height * sizeof(DWORD));
BITMAPINFOHEADER biheader = { sizeof(biheader), width, height, 1, 32, BI_RGB };
LPVOID bits;
auto hbitmap = CreateDIBSection(hdc, (BITMAPINFO*)&biheader, DIB_RGB_COLORS,
&bits, hMapFile, 0);
for(int i = 0; i < width * height; ++i)
buffer[i] = 0xFF0000;
auto memdc = CreateCompatibleDC(hdc);
auto oldhbitmap = SelectObject(memdc, hbitmap);
BitBlt(hdc, 0, 0, width, height, memdc, 0, 0, SRCCOPY);
for(int i = 0; i < width * height; ++i)
buffer[i] = 0;
BitBlt(hdc, 0, 0, 100, 100, memdc, 0, 0, SRCCOPY);
SelectObject(memdc, oldhbitmap); //<- ***EDIT***
//oldhbitmap is selected in to memdc, now we can destroy hbitmap and memdc
DeleteObject(hbitmap);
DeleteDC(memdc);
ReleaseDC(hwnd, hdc);
UnmapViewOfFile(buffer);
CloseHandle(hMapFile);
}
Side note, you don't gain anything by using reference operator & for constant values. Just change the function prototype as follows:
void createDeviceFromHWND(const HWND hwnd, const int width, const int height);
Also, this can be done without CreateFileMapping, and use buffer shown below. buffer will be valid as long as hbitmap is valid.
void test(const HWND hwnd, const int w, const int h)
{
auto hdc = GetDC(hwnd);
//use the negative value of height, so bitmap bits are not upside-down
BITMAPINFOHEADER bi = { sizeof(bi), w, -h, 1, 32, BI_RGB };
DWORD* buffer;
auto hbitmap = CreateDIBSection(hdc, (BITMAPINFO*)&bi, DIB_RGB_COLORS,
(void**)&buffer, NULL, 0);
auto memdc = CreateCompatibleDC(hdc);
auto oldbmp = SelectObject(memdc, hbitmap);
for(int i = 0; i < w * h; ++i) buffer[i] = 0xFF0000;
BitBlt(hdc, 0, 0, w, h, memdc, 0, 0, SRCCOPY);
//draw black square on top-left
for(int y = 0; y < 100; y++)
for(int x = 0; x < 100; x++)
buffer[y * w + x] = 0;
BitBlt(hdc, 0, 0, 100, 100, memdc, 0, 0, SRCCOPY);
//cleanup:
SelectObject(memdc, oldbmp);
DeleteObject(hbitmap); //<- buffer is not valid after hbitmap is destroyed
DeleteDC(memdc);
ReleaseDC(hwnd, hdc);
}
This approach is wrong. When the target window gets WM_PAINT all your work will be undone.
Always paint your windows the way you want them with WM_PAINT and BeginPaint.
You are not editing the bitmap here:
for (unsigned int i = 0; i < width * height; ++i)
{
mBackBuffer[i] = 0;
}
just filling the array, the bitmap was created from, with nulls.
According to MSDN documentation on GDI function RealizePalette():
The RealizePalette function modifies the palette for the device
associated with the specified device context. If the device context is
a memory DC, the color table for the bitmap selected into the DC is
modified.
Behavior described in italics doesn't seem to work in the following code:
void test_color_tbl_modify(HWND hWnd) {
// initialize BITMAPINFO struct for a mono bitmap(red&white)
const int bmp_w = 16, bmp_h = 32;
std::vector<BYTE> vBytes(sizeof(BITMAPINFO) + sizeof(RGBQUAD) * 2); // for mono bitmaps, bmiColors member of BITMAPINFO contains two RGBQUAD elems
BITMAPINFO* pbmi = reinterpret_cast<BITMAPINFO*>(vBytes.data());
{
BITMAPINFOHEADER bih{};
{
bih.biSize = sizeof(BITMAPINFOHEADER);
bih.biWidth = bmp_w;
bih.biHeight = bmp_h;
bih.biPlanes = 1;
bih.biBitCount = 1;
bih.biCompression = BI_RGB;
bih.biSizeImage = ((bih.biWidth * bih.biBitCount + 31) & ~31) / 8 // each scanline aligned on DWORD boundary
* bih.biHeight;
bih.biClrUsed = 2;
bih.biClrImportant = 0;
}
pbmi->bmiHeader = bih;
pbmi->bmiColors[0] = RGBQUAD{0,0,255,0}; // red
pbmi->bmiColors[1] = RGBQUAD{255,255,255,0}; // white
}
// create a mono DDB
HDC hdc = GetDC(hWnd);
HDC hdcmem = CreateCompatibleDC(hdc); // has 1x1 mono bitmap selected into it by default
HBITMAP hbitmap = CreateCompatibleBitmap(hdcmem, bmp_w, bmp_h); // creates a mono-bitmap(see above)
// draw something
HGDIOBJ hOldBmp = SelectObject(hdcmem, hbitmap);
for(int y = 0; y < bmp_h; ++y) {
for(int x = 0; x < bmp_w; ++x) {
COLORREF col = x & 1 && y & 1 ? RGB(255, 255, 255) : RGB(0, 0, 0);
SetPixel(hdcmem, x, y, col);
}
}
// blit image to client area by creating a DIB section and
// copying DIBits to it from hbitmap(works as expected: red&white image)
{
// get DIBits
std::vector<BYTE> vDIBits_buf(pbmi->bmiHeader.biSizeImage);
void* pvBits = vDIBits_buf.data();
SelectObject(hdcmem, hOldBmp); // hbitmap must NOT be selected into a DC before GetDIBits() call as per documentation
if(!GetDIBits(hdc, hbitmap,
0, (UINT)bmp_h,
pvBits, pbmi, DIB_RGB_COLORS)) { // resets biClrUsed & biClrImportant to 0, and pbmi->bmiColors to black&white -- why??
MessageBox(hWnd, L"GetDIBits has failed", L"Failed", MB_OK);
}
// reset members modified(for some reason) by GetDIBits()
// back to their original values
pbmi->bmiHeader.biClrUsed = 2;
pbmi->bmiColors[0] = RGBQUAD{0,0,255,0};
pbmi->bmiColors[1] = RGBQUAD{255,255,255,0};
// copy DIBits from hbitmap to hDIBSecion
void* pvBits_dest = nullptr;
HBITMAP hDIBSecion = CreateDIBSection(hdc, pbmi, DIB_RGB_COLORS, &pvBits_dest, NULL, 0);
memcpy(pvBits_dest, pvBits, pbmi->bmiHeader.biSizeImage);
// blit hDIBSecion to client area
HGDIOBJ hOldBmp = SelectObject(hdcmem, hDIBSecion);
BitBlt(hdc, 0, 0, bmp_w, bmp_h, hdcmem, 0, 0, SRCCOPY); // blits a red&white image as expected
// clean up
SelectObject(hdcmem, hOldBmp);
DeleteObject(hDIBSecion);
}
// blit image to client area by modifying color table of hbitmap
// (does not work as expected: black&white image instead of green&black)
{
// initialize palette(green&black)
std::vector<BYTE> log_palette_buf(sizeof(LOGPALETTE) + sizeof(PALETTEENTRY) * 2);
LOGPALETTE* plplt = reinterpret_cast<LOGPALETTE*>(log_palette_buf.data());
plplt->palNumEntries = 2;
plplt->palVersion = 0x0300;
PALETTEENTRY pe_black{0,0,0,0};
PALETTEENTRY pe_green{0,255,0,0};
plplt->palPalEntry[0] = pe_green;
plplt->palPalEntry[1] = pe_black;
// modify color table of hbitmap to green&black
HGDIOBJ hOldBmp = SelectObject(hdcmem, hbitmap); // select hbitmap into memory DC first
HPALETTE hp = CreatePalette(plplt);
HPALETTE hp_old = SelectPalette(hdcmem, hp, FALSE);
RealizePalette(hdcmem); // supposed to modify color table of selected bitmap(hbitmap) according to documentation
// blit hbitmap to client area
BitBlt(hdc, bmp_w, 0, bmp_w, bmp_h, hdcmem, 0, 0, SRCCOPY); // ???blits a black&white image???
// clean-up
SelectObject(hdcmem, hOldBmp);
SelectPalette(hdcmem, hp_old, FALSE);
DeleteObject(hp);
}
// clean up
DeleteObject(hbitmap);
DeleteDC(hdcmem);
ReleaseDC(hWnd, hdc);
}
What am I missing?
I have a pointer to RGB data (640x480x3 bytes) that I want to draw into a window using BitBlt or something else equally fast. How do I convert the RGB data into something usable with BitBlt (for example).
Here is what I tried so far (without success)
unsigned char *buf = theVI->getPixels(0);
int size = theVI->getSize(0);
int h = theVI->getHeight(0);
int w = theVI->getWidth(0);
HDC dc = GetDC(hwnd);
HDC dcMem = CreateCompatibleDC(dc);
HBITMAP bmp = CreateBitmap(w, h, 1, 24, buf);
SelectObject(dcMem, bmp);
BitBlt(dc, 0, 0, w, h, dcMem, 0, 0, SRCCOPY);
Thanks
UPDATE: this is the working code...
HDC dc = GetDC(hwnd);
BITMAPINFO info;
ZeroMemory(&info, sizeof(BITMAPINFO));
info.bmiHeader.biBitCount = 24;
info.bmiHeader.biWidth = w;
info.bmiHeader.biHeight = h;
info.bmiHeader.biPlanes = 1;
info.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
info.bmiHeader.biSizeImage = size;
info.bmiHeader.biCompression = BI_RGB;
StretchDIBits(dc, 0, 0, w, h, 0, 0, w, h, buf, &info, DIB_RGB_COLORS, SRCCOPY);
ReleaseDC(hwnd, dc);
You can render your bytes ( that are so called DIB device independent bitmap ) to HDC using StretchDIBits API function.
And yet check DIB article in MSDN