HDC to HDC for HDC [closed] - c

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I would like to blit hdc to an other hdc, and this hdc will be blit into hdc containing "BeginPaint". But a problem appears, nothing have been drawn.
this is the code, thanks,
HDC hdcMem3 = CreateCompatibleDC(NULL);
SelectObject(hdcMem3, Picture);
BITMAP bitmap;
GetObject(Picture, sizeof(bitmap), &bitmap);
HDC hdcMem2 = CreateCompatibleDC(NULL);
BitBlt(hdcMem2, 0, 0, bitmap.bmWidth, bitmap.bmHeight, hdcMem3, 0, 0, SRCCOPY);
DeleteDC(hdcMem3);
BitBlt(hdcMem, 0, 0, bitmap.bmWidth, bitmap.bmHeight, hdcMem2, 0, 0, SRCCOPY);
DeleteDC(hdcMem2);

Answer 1

CreateCompatibleDC creates a device context with a 1-pixel monochrome bitmap.
In your example, the device context referenced by hdcMem3 has a real bitmap, but the DC referenced by hdcMem2 has only the 1-pixel monochrome bitmap. When you blit from hdcMem3 to hdcMem2, you probably end up with 1 black pixel.
What you need is to create a memory bitmap to select into hdcMem2. I assume that, eventually, you're going to display this in a window. Let's assume that you have a device context for the window called hdcWindow.
// Create a memory bitmap that's compatible with the window (screen) and
// the same size as Picture.
hbmpMem2 = CreateCompatibleBitmap(hdcWindow, bitmap.bmWidth, bitmap.bmHeight);
hbmpOld2 = SelectObject(hdcMem2, hbmpMem2);
Now when you do stuff to hdcMem2, it will draw to a real bitmap.
When you're done with hdcMem2, you need to first take care of hbmpMem2:
SelectObject(hdcMem2, hbmpOld2);
DeleteObject(hbmpMem2);
DestroyDC(hdcMem2);

Answer 2

Okay work ! but i've found one thing see :
BITMAP bitmap;
GetObject(picture, sizeof(bitmap), &bitmap);
LPBITMAPINFO Hbitmap = new BITMAPINFO;
Hbitmap->bmiHeader.biSize = sizeof(Hbitmap->bmiHeader);
Hbitmap->bmiHeader.biWidth = 300;
Hbitmap->bmiHeader.biHeight = 300;
Hbitmap->bmiHeader.biPlanes = 1;
Hbitmap->bmiHeader.biBitCount = 32;
Hbitmap->bmiHeader.biCompression = BI_RGB;
Hbitmap->bmiHeader.biSizeImage = 300 * 4 * 300;
Hbitmap->bmiHeader.biClrUsed = 0;
Hbitmap->bmiHeader.biClrImportant = 0;
HDC hdcMem3 = CreateCompatibleDC(NULL);
SelectObject(hdcMem3, picture);
HDC hdcMem2 = CreateCompatibleDC(NULL);
HBITMAP BhdcMem2 = CreateDIBSection(hdcMem2, Hbitmap, DIB_RGB_COLORS,0, 0, 0);
SelectObject(hdcMem2, BhdcMem2);
BitBlt(hdcMem2, 0, 0, bitmap.bmWidth, bitmap.bmHeight, hdcMem3, 0, 0, SRCCOPY);
BitBlt(hdcMem, 0, 0, bitmap.bmWidth, bitmap.bmHeight, hdcMem2, 0, 0, SRCCOPY);
DeleteDC(hdcMem2);
DeleteDC(hdcMem3);
delete Hbitmap;