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I have an HBITMAP handle to a device-dependent bitmap, resulting from this code:
// copy screen to bitmap
HDC hScreen = GetDC(NULL);//don't use hwnd, it doesn't work for non native windows
HDC hDC = CreateCompatibleDC(hScreen);
HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, w, h);
HGDIOBJ old_obj = SelectObject(hDC, hBitmap);
BOOL bRet = BitBlt(hDC, 0, 0, w, h, hScreen, x1, y1, SRCCOPY);
I want to access (read-only) the bits of the bitmap, read some values, do some calculations, then discard it.
According to this answer, I shouldn't use GetDIBits() or GetBitmapBits() since they copy the data, but instead I should use:
BITMAP bitmap;
GetObject(hBitmap, sizeof(bitmap), (LPVOID)&bitmap);
But according to GetObject's documentation:
If hgdiobj is a handle to a bitmap created by calling CreateDIBSection, and the specified buffer is large enough, the GetObject function returns a DIBSECTION structure. In addition, the bmBits member of the BITMAP structure contained within the DIBSECTION will contain a pointer to the bitmap's bit values.
If hgdiobj is a handle to a bitmap created by any other means, GetObject returns only the width, height, and color format information of the bitmap. You can obtain the bitmap's bit values by calling the GetDIBits or GetBitmapBits function.
Which is pointed to in a comment on the above answer:
According to this https://msdn.microsoft.com/en-us/library/dd144904(v=vs.85).aspx if bitmap is not created by CreateDIBSection bitmap.bmBit pointer will be null.
So, is there anyway to access the bits of the bitmap (RGB values), without copying them?
If it helps, the device on which the bitmap is dependent is always a screen, so I guess it's always a 24bit or 32bit bitmap.
In this article, regarding how to save an HBITMAP to a file, there's this section:
// Allocate memory for the BITMAPINFO structure. (This structure
// contains a BITMAPINFOHEADER structure and an array of RGBQUAD
// data structures.)
if (cClrBits < 24) pbmi = (PBITMAPINFO)LocalAlloc(LPTR, sizeof(BITMAPINFOHEADER) + sizeof(RGBQUAD) * (1 << cClrBits));
// There is no RGBQUAD array for these formats: 24-bit-per-pixel or 32-bit-per-pixel
else pbmi = (PBITMAPINFO)LocalAlloc(LPTR, sizeof(BITMAPINFOHEADER));
So, I don't really understand what's happening here, and which is right?
I want to use GDI+ method Image::Save() to save a DDB to a file in the following scenario:
HBITMAP hBitmap = CreateCompatibleBitmap(hDC, 200, 200) ;
...
//hBitmap is a DDB so I need to pass an HPALETTE
Gdiplus::Bitmap(hBitmap, ???HPALETTE??? ).Save(L"file.png", ...) ;
The problem is that Bitmap constructor asks for an HPALETTE when the bitmap is not a device-independent bitmap.
Where do I get the necessary HPALETTE from?
FOLLOWUP:
One of the answers suggests passing NULL as the HPALETTE parameter.
Here is a working example that does so. The result is a purely black and white image where all colors are lost.
#include <windows.h>
#include <gdiplus.h>
int main(){
using namespace Gdiplus ;
GdiplusStartupInput gdiplusStartupInput ;
ULONG_PTR gdiplusToken ;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL) ;
CLSID pngEncoder = {0x557cf406, 0x1a04, 0x11d3, {0x9a, 0x73, 0x00, 0x00, 0xf8, 0x1e, 0xf3, 0x2e} } ;
HDC dcHndl = CreateCompatibleDC(NULL) ;
HBITMAP hBitmap = CreateCompatibleBitmap(dcHndl, 200, 200) ;
SelectObject(dcHndl, hBitmap) ;
BitBlt(dcHndl, 0,0, 200,200, GetDC(NULL), 0,0, SRCCOPY|CAPTUREBLT) ;
Bitmap(hBitmap, NULL).Save(L"file.png", &pngEncoder) ;
}
First (and this is unrelated to your main question):
When creating a bitmap for screen shot, don't use a memory dc because that creates a monochrome bitmap. That's the main reason you are getting a black and white image (on my computer I just get a black image).
Don't use GetDC(0) inside another function. Every call to GetDC match have a matching ReleaseDC to avoid resource leak.
After calling BitBlt it is good practice to select hbitmap out of dc because you are basically finished drawing on dc.
The following code will work on Windows 10
int w = 800;
int h = 600;
HDC hdc = GetDC(HWND_DESKTOP);
HDC memdc = CreateCompatibleDC(hdc);
HBITMAP hbitmap = CreateCompatibleBitmap(hdc, w, h);
HBITMAP oldbmp = (HBITMAP)SelectObject(memdc, hbitmap);
BitBlt(memdc, 0, 0, w, h, hdc, 0, 0, SRCCOPY | CAPTUREBLT);
SelectObject(memdc, oldbmp);
Bitmap(hbitmap, NULL).Save(filename, &pngEncoder);
DeleteObject(hbitmap);
DeleteDC(memdc);
ReleaseDC(HWND_DESKTOP, hdc);
Back to your question regarding the documentation:
Type: HPALETTE
Handle to a GDI palette used to define the bitmap colors if hbm is not a device-independent bitmap (DIB).
In addition,
Do not pass to the Bitmap::FromHBITMAP method a GDI bitmap or a GDI palette that is currently (or was previously) selected into a device context.
The code I posted obeys only one rule, that GDI bitmap is not currently selected in to a device context (but it was previously selected).
The documentation may apply to older versions of Windows. As far as I can see MFC's CImage class does not follow all these rules. New computer displays are all 24 or 32 bit, I don't know how you would get a palette for it.
To follow the documentation to the letter, you can convert DDB to DIB section, using CreateDIBSection and GetDIBits. Use the new DIB section hbitmap_dib in Bitmap::FromHBITMAP. This will satisfy all of the conditions: hbitmap is dib, it is not (and was not) selected in to a device context.
Or, Gdiplus::Bitmap has another method Bitmap::FromBITMAPINFO. If there is no palette, you can use this code instead:
HDC hdc = GetDC(HWND_DESKTOP);
HDC memdc = CreateCompatibleDC(hdc);
HBITMAP hbitmap = CreateCompatibleBitmap(hdc, w, h);
HBITMAP oldbmp = (HBITMAP)SelectObject(memdc, hbitmap);
BitBlt(memdc, 0, 0, 800, 600, hdc, 0, 0, SRCCOPY | CAPTUREBLT);
SelectObject(memdc, oldbmp);
BITMAP bm;
GetObject(hbitmap, sizeof(bm), &bm);
int size = ((bm.bmWidth * bm.bmBitsPixel + 31) / 32) * 4 * bm.bmHeight;
BITMAPINFO info{ sizeof(info), bm.bmWidth, bm.bmHeight, 1, bm.bmBitsPixel, BI_RGB, size };
std::vector<char> bits(size);
GetDIBits(memdc, hbitmap, 0, bm.bmHeight, &bits[0], &info, DIB_RGB_COLORS);
Bitmap *bitmap = Bitmap::FromBITMAPINFO(&info, &bits[0]);
bitmap->Save(filename, &pngEncoder);
delete bitmap;
DeleteObject(hbitmap);
DeleteDC(memdc);
ReleaseDC(HWND_DESKTOP, hdc);
As CreateCompatibleBitmap remarks sate if you are dealing with color bitmaps we can also assume that hDC is a nonmemory device context (because memory device context will only create monochrome bitmaps) and the color palette used by this bitmap is the same color palette used by this device context. You can query it using GetCurrentObject method. However remarks to Bitmap.Bitmap(HBITMAP, HPALETTE) constructor state:
Do not pass to the GDI+ Bitmap::Bitmap constructor a GDI bitmap or a GDI palette that is currently (or was previously) selected into a device context.
So you can not used current device context palette directly and need to create a copy of it instead.
/// <returns>
/// Handle to palette currently selected into device context without granting ownership.
/// </returns>
_Check_return_ ::HPALETTE
Fetch_CurrentPalette(_In_ ::HDC const h_dc)
{
assert(h_dc);
::HGDIOBJ const h_palette_object{::GetCurrentObject(h_dc, OBJ_PAL)}; // not owned
assert(h_palette_object);
assert(OBJ_PAL == ::GetObjectType(h_palette_object));
// Perform unchecked conversion of generic GDI object descriptor to GDI palette descriptor.
::HPALETTE h_current_palette{}; // not owned
{
static_assert(sizeof(h_palette_object) == sizeof(h_current_palette), "wat");
::memcpy
(
::std::addressof(h_current_palette)
, ::std::addressof(h_palette_object)
, sizeof(h_current_palette)
);
}
return(h_current_palette);
}
/// <returns>
/// Handle to palette copy with granting ownership.
/// </returns>
_Check_return_ ::HPALETTE
Make_PaletteCopy(_In_ ::HPALETTE const h_palette)
{
assert(h_palette);
::UINT const first_entry_index{};
::UINT entries_count{};
::LPPALETTEENTRY p_entries{};
// Figure out how many entries palette contains.
entries_count = ::GetPaletteEntries(h_palette, first_entry_index, entries_count, p_entries);
assert(1 < entries_count);
assert(entries_count <= ::std::numeric_limits< decltype(LOGPALETTE::palNumEntries) >::max());
// This buffer will hold palette description which contains first PALETTEENTRY as last field.
// followed by the rest of PALETTEENTRY items.
::std::unique_ptr< ::std::uint8_t[] > const p_buffer
{
new ::std::uint8_t[sizeof(::LOGPALETTE) + (sizeof(::PALETTEENTRY) * (entries_count - 1u))]
};
// Perform unchecked conversion of buffer pointer to palette description pointer.
::LOGPALETTE * p_description{};
{
::std::uint8_t * const p_buffer_bytes{p_buffer.get()};
static_assert(sizeof(p_buffer_bytes) == sizeof(p_description), "wat");
::memcpy
(
::std::addressof(p_description)
, ::std::addressof(p_buffer_bytes)
, sizeof(p_description)
);
}
// Copy palette entries into buffer.
p_entries = static_cast< ::LPPALETTEENTRY >(p_description->palPalEntry);
::UINT const copied_entries_count
{
::GetPaletteEntries(h_palette, first_entry_index, entries_count, p_entries)
};
assert(copied_entries_count == entries_count);
// Create palette copy.
p_description->palVersion = 0x300; // magic
p_description->palNumEntries = static_cast< ::WORD >(copied_entries_count);
::HPALETTE const h_copied_palette{::CreatePalette(p_description)}; // owned
assert(h_copied_palette);
return(h_copied_palette);
}
::HPALETTE const hPal{Make_PaletteCopy(Fetch_CurrentPalette(hDC))}; // owned
assert(hPal);
::HBITMAP const hBitmap{::CreateCompatibleBitmap(hDC, 200, 200)}; // owned
assert(hBitmap);
{
::Gdiplus::Bitmap bmp{hBitmap, hPal};
assert(::Gdiplus::Status::Ok == bmp.GetLastStatus());
// Do something...
}
// Delete palette and bitmap after GDI+ bitmap object went out of scope.
if(FALSE == ::DeleteObject(hPal))
{
assert(false);
}
if(FALSE == ::DeleteObject(hBitmap))
{
assert(false);
}
You can pass NULL. Sample code below.
int main()
{
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
GUID encoder = {};
GetGdiplusEncoderClsid(L"image/png", &encoder); // https://stackoverflow.com/a/5346026/104458
HDC hdc = GetDC(NULL);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, 200, 200);
Bitmap bmp(hBitmap, NULL);
bmp.Save(L"File.png", &encoder);
return 0;
}
How to convert HICON to HBITMAP in VC++?
I know this is an FAQ but all the solutions I've found on Google don't work. What I need is a function which takes a parameter HICON and returns HBITMAP.
Greatest if possible to make conversion to 32-bit bitmap even the icon is 24-bit, 16-bit or 8-bit.
This is the code, I don't know where it goes wrong:
HBITMAP icon_to_bitmap(HICON Icon_Handle) {
HDC Screen_Handle = GetDC(NULL);
HDC Device_Handle = CreateCompatibleDC(Screen_Handle);
HBITMAP Bitmap_Handle =
CreateCompatibleBitmap(Device_Handle,GetSystemMetrics(SM_CXICON),
GetSystemMetrics(SM_CYICON));
HBITMAP Old_Bitmap = (HBITMAP)SelectObject(Device_Handle,Bitmap_Handle);
DrawIcon(Device_Handle, 0,0, Icon_Handle);
SelectObject(Device_Handle,Old_Bitmap);
DeleteDC(Device_Handle);
ReleaseDC(NULL,Screen_Handle);
return Bitmap_Handle;
}
this code do it:
HICON hIcon = (HICON)LoadImage(instance, MAKEINTRESOURCEW(IDI_ICON), IMAGE_ICON, width, height, 0);
ICONINFO iconinfo;
GetIconInfo(hIcon, &iconinfo);
HBITMAP hBitmap = iconinfo.hbmColor;
and this is the code in the *.rc file:
IDI_ICON ICON "example.ico"
and this is the code in the *.h file:
#define IDI_ICON 4000
HDC hDC = GetDC(NULL);
HDC hMemDC = CreateCompatibleDC(hDC);
HBITMAP hMemBmp = CreateCompatibleBitmap(hDC, x, y);
HBITMAP hResultBmp = NULL;
HGDIOBJ hOrgBMP = SelectObject(hMemDC, hMemBmp);
DrawIconEx(hMemDC, 0, 0, hIcon, x, y, 0, NULL, DI_NORMAL);
hResultBmp = hMemBmp;
hMemBmp = NULL;
SelectObject(hMemDC, hOrgBMP);
DeleteDC(hMemDC);
ReleaseDC(NULL, hDC);
DestroyIcon(hIcon);
return hResultBmp;
I don't have code readily available to share, but I think this is pretty easy. You have to create the HBITMAP, create a device context, select the bitmap into the DC (this will make the bitmap the drawing area for this DC). Finally call the DrawIcon() function to draw your icon on this DC. After that detach the bitmap from the DC and destroy the DC. Your bitmap now should be ready to go.
Update after looking at your code:
I believe the problem is in the createCompatibleBitmap call. You are asking for a bitmap compatible with the memory DC, but memory DCs start with a 1 bit/pixel bitmap selected into them. Try asking for a bitmap compatible with the screen DC instead.
Update 2: you may want to look at this question as it seems related to your problem.
I found this(similar code works for me - 32x32 icons with or without alpha data):
used CopyImage (msdn link)
HICON hICON = /*your code here*/
HBITMAP hBITMAPcopy;
ICONINFOEX IconInfo;
BITMAP BM_32_bit_color;
BITMAP BM_1_bit_mask;
// 1. From HICON to HBITMAP for color and mask separately
//.cbSize required
//memset((void*)&IconInfo, 0, sizeof(ICONINFOEX));
IconInfo.cbSize = sizeof(ICONINFOEX);
GetIconInfoEx( hICON , &IconInfo);
//HBITMAP IconInfo.hbmColor is 32bit per pxl, however alpha bytes can be zeroed or can be not.
//HBITMAP IconInfo.hbmMask is 1bit per pxl
// 2. From HBITMAP to BITMAP for color
// (HBITMAP without raw data -> HBITMAP with raw data)
// LR_CREATEDIBSECTION - DIB section will be created,
// so .bmBits pointer will not be null
hBITMAPcopy = (HBITMAP)CopyImage(IconInfo.hbmColor, IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION);
// (HBITMAP to BITMAP)
GetObject(hBITMAPcopy, sizeof(BITMAP), &BM_32_bit_color);
//Now: BM_32_bit_color.bmBits pointing to BGRA data.(.bmWidth * .bmHeight * (.bmBitsPixel/8))
// 3. From HBITMAP to BITMAP for mask
hBITMAPcopy = (HBITMAP)CopyImage(IconInfo.hbmMask, IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION);
GetObject(hBITMAPcopy, sizeof(BITMAP), &BM_1_bit_mask);
//Now: BM_1_bit_mask.bmBits pointing to mask data (.bmWidth * .bmHeight Bits!)
BM_32_bit_color bitmap may be have Alpha *channel*(each 4th byte) already set! So - check for it before u add mask bit to color data.
was using XP without issue for a long time. switched to 7 and trying to capture screenshots with my previously functioning code no longer works. simple concept and relatively generic code...just find the window that i call and save it as a .png. any ideas what might make this bad boy run again? can't debug with my current setup, but it makes it all the way and spits out the error message after bmp->save(...) ...couldn't save image file. edit: also a file does get created/saved, but it is blank and not written to. perhaps the bitmap encoding or GDI is screwed up?
bool CScreenShot::Snap(CString wintitle, CString file, CString& ermsg)
{
ermsg = ""; // no error message
// create screen shot bitmap
EnumWinProcStruct prm = {0, (LPSTR)(LPCTSTR)wintitle, 0};
// Find the descriptor of the window with the caption wintitle
EnumDesktopWindows(0, EnumWindowsProc, (LPARAM)&prm);
if(!prm.hwnd)
{
ermsg.Format("couldn't find window \"%s\"", wintitle);
return false;
}
// Make the window the topmost window
SetWindowPos(prm.hwnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE);
Sleep(300);
// Get device context for the top-level window and client rect
HDC hDC = GetDC(prm.hwnd);
RECT rc;
GetClientRect(prm.hwnd, &rc);
HDC memDC = CreateCompatibleDC(hDC);
// Set the size and color depth for the screen shot image
BITMAPINFO bmpInfo;
memset(&bmpInfo, 0, sizeof(bmpInfo));
bmpInfo.bmiHeader.biSize = sizeof(bmpInfo.bmiHeader);
bmpInfo.bmiHeader.biWidth = rc.right - rc.left;
bmpInfo.bmiHeader.biHeight = rc.bottom - rc.top;
bmpInfo.bmiHeader.biPlanes = 1;
bmpInfo.bmiHeader.biBitCount = 24;
bmpInfo.bmiHeader.biCompression = BI_RGB;
bmpInfo.bmiHeader.biSizeImage = bmpInfo.bmiHeader.biWidth * bmpInfo.bmiHeader.biHeight * 3;
// Create memory buffer and perform a bit-block transfer of the color data from the window to the memory
LPVOID addr;
HBITMAP memBM = CreateDIBSection(memDC, &bmpInfo, DIB_RGB_COLORS, &addr, 0, 0);
HGDIOBJ stdBM = SelectObject(memDC, memBM);
BOOL OK = BitBlt(memDC, 0, 0, bmpInfo.bmiHeader.biWidth, bmpInfo.bmiHeader.biHeight, hDC, 0, 0, SRCCOPY);
ReleaseDC(prm.hwnd, hDC);
SetWindowPos(prm.hwnd, HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE);
// Initialize GDI+.
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
if(GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL) != Ok)
{
ermsg.Format("couldn't start GDI+");
return false;
}
// Create a Bitmap object for work with images defined by pixel data from the GDI HBitmap and the GDI HPalette.
Bitmap* bmp = ::new Bitmap(memBM, DIB_RGB_COLORS);
SelectObject(memDC, stdBM);
DeleteObject(memBM);
DeleteDC(memDC);
// Find the encoder for "image/png" mime type
CLSID encoderClsid;
EncoderParameters encoderParameters;
GetEncoderClsid(L"image/png", &encoderClsid);
encoderParameters.Count = 0;
// Convert file name to Unicode (wide-char) string.
WCHAR fn[_MAX_PATH];
MultiByteToWideChar(CP_THREAD_ACP, MB_PRECOMPOSED, file, file.GetLength() + 1, fn, _MAX_PATH);
// Save the screen shot into the specified file using image encoder with the mime style "image/png"
if(bmp->Save(fn, &encoderClsid, &encoderParameters) != Ok)
{
ermsg.Format("couldn't save image file \"%s\"", file);
return false;
}
::delete bmp;
GdiplusShutdown(gdiplusToken);
return true;
}
The error message implies that you're trying to save the file to a folder that you don't have permission to write to. Many folders such as Program Files are now protected. Since you didn't include the path in your sample code I'm unable to determine if this is the actual problem.
Edit: Another possibility is that the Bitmap is improperly constructed which causes the Save to fail. The second parameter to the constructor is supposed to be a handle to a palette, I think DIB_RGB_COLORS would be invalid here and you should use NULL. Also there are a couple of caveats noted in the Microsoft documentation and perhaps the different OS versions react differently when you break the rules:
You are responsible for deleting the GDI bitmap and the GDI palette. However, you should not delete the GDI bitmap or the GDI palette until after the GDI+ Bitmap::Bitmap object is deleted or goes out of scope.
Do not pass to the GDI+ Bitmap::Bitmap constructor a GDI bitmap or a GDI palette that is currently (or was previously) selected into a device context.
win7 won't accept encoderParameters.Count == 0 for some reason. Set that == 1 and you should be all set.
you probably could also just remove that parameter from Save() (overloaded)
In my code I quickly generate images on the fly, and I want to display them as quickly as possible. So the first time I create my image, I create a new BITMAP, but instead of deleting the old one and creating a new one for every subsequent image, I just want to copy my data back into the existing one. Here is my code to do both the initial creation and the updating. The creation works just fine, but the updating one doesn't work.
BITMAPINFO bi;
HBITMAP Frame::CreateBitmap(HWND hwnd, int tol1, int tol2, bool useWhite, bool useBackground)
{
ZeroMemory(&bi.bmiHeader, sizeof(BITMAPINFOHEADER));
bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bi.bmiHeader.biWidth = width;
bi.bmiHeader.biHeight = height;
bi.bmiHeader.biPlanes = 1;
bi.bmiHeader.biBitCount = 24;
bi.bmiHeader.biCompression = BI_RGB;
ZeroMemory(bi.bmiColors, sizeof(RGBQUAD));
// Allocate memory for bitmap bits
int size = height * width;
Pixel* newPixels = new Pixel[size];
// Recompute the output
//memcpy(newPixels, pixels, size*3);
ComputeOutput(newPixels, tol1, tol2, useWhite, useBackground);
HBITMAP bitmap = CreateDIBitmap(GetDC(hwnd), &bi.bmiHeader, CBM_INIT, newPixels, &bi, DIB_RGB_COLORS);
delete newPixels;
return bitmap;
}
and
void Frame::UpdateBitmap(HWND hwnd, HBITMAP bitmap, int tol1, int tol2, bool useWhite, bool useBackground)
{
ZeroMemory(&bi.bmiHeader, sizeof(BITMAPINFOHEADER));
bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
HDC hdc = GetDC(hwnd);
if(!GetDIBits(hdc, bitmap, 0, bi.bmiHeader.biHeight, NULL, &bi, DIB_RGB_COLORS))
MessageBox(NULL, "Can't get base image info!", "Error!", MB_ICONEXCLAMATION | MB_OK);
// Allocate memory for bitmap bits
int size = height * width;
Pixel* newPixels = new Pixel[size];
// Recompute the output
//memcpy(newPixels, pixels, size*3);
ComputeOutput(newPixels, tol1, tol2, useWhite, useBackground);
// Push back to windows
if(!SetDIBits(hdc, bitmap, 0, bi.bmiHeader.biHeight, newPixels, &bi, DIB_RGB_COLORS))
MessageBox(NULL, "Can't set pixel data!", "Error!", MB_ICONEXCLAMATION | MB_OK);
delete newPixels;
}
where the Pixel struct is just this:
struct Pixel { unsigned char b, g, r; };
Why does my update function not work. I always get the MessageBox for "Can't set pixel data!" I used code similar to this when I was loading in the original bitmap from file, then editing the data, but now when I manually create it, it doesn't work.
to write to a bitmap you have to Select it into a DeviceContext:
hdcMemDC = CreateCompatibleDC(hdc);
... // adjust hdcMem to right sizes (see MSDN : Capturing an Image)
SelectObject(hdcMemDC,bitmap);
... // your Bitmap drawing
BitBlt( hdcMemDC, ... ) // to copy to hdc.
ReleaseDC(hWnd, hdcMemDC);
Also CreateDIBitmap( GetDC(hwnd),... ) needs a ReleaseDC(hWnd ,??? );
You must assign GetDC(...) to a variable so you can release it.
Please, create your bitmap with CreateDIBSection.
This creates a HBITMAP to a bitmap and returns a pointer to a usermode accessible buffer. In the format you specify.