I have an HBITMAP provided by a 3rd party library, and need to write it rescaled on disk as a JPEG.
I have never used WIC, so I've been following this tutorial: https://msdn.microsoft.com/en-us/library/windows/desktop/ff973956.aspx
I have created a WicBitmap from my HBITMAP.
In Listing 9 it becomes apparent that I need a decoder, but the only way to create it I have found is with IWICImagingFactory::CreateDecoderFromFilename. There is an Initialize method that receives a IStream, but I'm not sure of the correct way to use it.
Is this the correct way to save an HBITMAP to disk? If so, how can I get a decoder from my HBITMAP or WicBitmap?
IWICImagingFactory::CreateBitmapFromHBITMAP imports GDI bitmap into WIC as decoded bitmap for which you already need no decoder. That is, you are good to go with your encoding part and saving to disk.
The code snippet below does gets it done in full: 800x600 bitmap from the top left desktop corner as HBITMAP and then saved into JPEG file.
#include "stdafx.h"
#include <wincodecsdk.h>
#include <atlbase.h>
#define __C ATLENSURE_SUCCEEDED
int _tmain(int argc, _TCHAR* argv[])
{
CoInitialize(NULL);
{
HBITMAP hBitmap;
{
HDC hDc = GetDC(NULL);
hBitmap = CreateCompatibleBitmap(hDc, 800, 600);
HDC hBitmapDc = CreateCompatibleDC(hDc);
HGDIOBJ hPreviousBitmap = SelectObject(hBitmapDc, hBitmap);
BitBlt(hBitmapDc, 0, 0, 800, 600, hDc, 0, 0, SRCCOPY);
SelectObject(hBitmapDc, hPreviousBitmap);
DeleteDC(hBitmapDc);
ReleaseDC(NULL, hDc);
}
CComPtr<IWICImagingFactory> pFactory;
__C(pFactory.CoCreateInstance(CLSID_WICImagingFactory));
CComPtr<IWICBitmap> pBitmap;
__C(pFactory->CreateBitmapFromHBITMAP(hBitmap, NULL, WICBitmapIgnoreAlpha, &pBitmap));
CComPtr<IWICBitmapEncoder> pBitmapEncoder;
__C(pFactory->CreateEncoder(GUID_ContainerFormatJpeg, NULL, &pBitmapEncoder));
CComPtr<IWICStream> pFileStream;
__C(pFactory->CreateStream(&pFileStream));
__C(pFileStream->InitializeFromFilename(L"D:\\Output.jpg", GENERIC_WRITE));
__C(pBitmapEncoder->Initialize(pFileStream, WICBitmapEncoderNoCache));
CComPtr<IWICBitmapFrameEncode> pBitmapFrameEncode;
CComPtr<IPropertyBag2> pPropertyBag;
__C(pBitmapEncoder->CreateNewFrame(&pBitmapFrameEncode, &pPropertyBag));
PROPBAG2 Property;
ZeroMemory(&Property, sizeof Property);
Property.pstrName = L"ImageQuality";
CComVariant vQuality(0.85f);
__C(pPropertyBag->Write(1, &Property, &vQuality));
__C(pBitmapFrameEncode->Initialize(pPropertyBag));
__C(pBitmapFrameEncode->WriteSource(pBitmap, NULL));
__C(pBitmapFrameEncode->Commit());
__C(pBitmapEncoder->Commit());
}
CoUninitialize();
return 0;
}
Related
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;
}
I have a bitmap class that has a load function for loading the bitmap from either file path or resource ID. This part works fine.
void GtBitmap::Load()
{
LPTSTR szFileName;
szFileName = (LPTSTR)m_strPath.c_str();
// Check for valid .BMP file path
if (m_strPath.size() > 0)
{
// Open .BMP file
m_pFile = fopen(m_strPath.c_str(), ("rb"));
if (m_pFile != NULL)
{
m_hBitmap = (HBITMAP)LoadImage (GetModuleHandle(NULL), szFileName, IMAGE_BITMAP, 0, 0, LR_SHARED | LR_LOADFROMFILE);
GetObject(m_hBitmap, sizeof(m_bmap), &m_bmap);
int i = 1;
}
}
else if (m_intResourceID != 0)
{
m_hBitmap = (HBITMAP)LoadImage(GetModuleHandle(NULL), MAKEINTRESOURCE(m_intResourceID), IMAGE_BITMAP, 0, 0, LR_SHARED);
GetObject(m_hBitmap, sizeof(m_bmap), &m_bmap);
int i = 1;
}
}
However, when I try to render it in my code block, the SelectObject returns null. Here is the code for that section of the painter class.
void GtPainterGDI::GtDrawBitmap(GtRectI & target, GtBitmap & bitmap, bool blnOffset)
{
GtCanvas topCv = m_arrCanvas.back();
HDC hdcMem = CreateCompatibleDC(topCv.m_hdcParent);
HBITMAP hbmOld = (HBITMAP)SelectObject(hdcMem, bitmap.m_hBitmap);
DWORD lastError = GetLastError();
bool success = BitBlt(hdcMem, target.GetLeft(), target.GetTop(),
target.Width(), target.Height(), hdcMem, 0, 0, SRCCOPY);
SelectObject(hdcMem, bitmap.m_hBitmap);
DeleteDC(hdcMem);
};
The SelectObject() returns null and the image is not drawn. I can only get the image to show up if I use a LoadImage() in that paint function. However I don't want to load the image every time I want to paint. I should be able to load the image once in the Load function or constructor of the bitmap, then use the handle in the paint function.
If anyone could please provide an example of loading an image in a constructor and then painting it elsewhere in the codes WM_PAINT or equivalent painting function I would appreciate it. The code is a new version of the GT graphical user interface library. I plan on posting a new version on codeproject in the next few days or so. I have to do some cleanup first...
Thanks in advance.
HINSTANCE parameter in LoadImage should be NULL when loading the image from file. Use GetModuleHandle(NULL) only when loading from resource.
m_hBitmap = (HBITMAP)LoadImage(NULL, m_strPath.c_str(),
IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
if (!m_hBitmap)
{
//report error
}
Also LR_SHARED is not necessary here.
When testing for file's exist, you can use std::ifstream. Example:
#include <fstream>
...
bool test = std::ifstream(m_strPath).good();
This will test for file and close the file handle right away.
Make sure to select hbmOld before deleting hdcMem:
HBITMAP hbmOld = (HBITMAP)SelectObject(hdcMem, bitmap.m_hBitmap);
BitBlt(...)
//SelectObject(hdcMem, bitmap.m_hBitmap); <<= remove this
SelectObject(hdcMem, hbmOld);
DeleteDC(hdcMem);
I'm trying to create a function which is equivalent to the windows API GetPixel() function, but I want to create a bitmap of my screen and then read that buffer.
This is what I've got (Mostly copy pasted from google searches), when I run it it only prints out 0's. I think I've got most of it right, and that my issue is that I don't know how to read the BYTE variable.
So my question is, what do I need to do in order to get it to print out some random colors (R,G or B) with my for loop?
#include <Windows.h>
#include <iostream>
#include <math.h>
#include <stdio.h>
using namespace std;
int main() {
HDC hdc,hdcMem;
hdc = GetDC(NULL);
hdcMem = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, 1680, 1050);
BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
// Get the BITMAPINFO structure from the bitmap
if(0 == GetDIBits(hdcMem, hBitmap, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error" << endl;
}
// create the bitmap buffer
BYTE* lpPixels = new BYTE[MyBMInfo.bmiHeader.biSizeImage];
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
MyBMInfo.bmiHeader.biBitCount = 32;
MyBMInfo.bmiHeader.biCompression = BI_RGB;
MyBMInfo.bmiHeader.biHeight = abs(MyBMInfo.bmiHeader.biHeight);
// get the actual bitmap buffer
if(0 == GetDIBits(hdc, hBitmap, 0, MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error2" << endl;
}
for(int i = 0; i < 100; i++) {
cout << (int)lpPixels[i] << endl;
}
return 0;
}
Windows 7
C::B 13.12 (Console Application)
Compiler: mingw32-gcc
Library gdi32 linked
As agreed, I'm adding a new answer with the working code snippet (I added the missing cleanup of lpPixels). See the discussions in my previous answer and the one made by #enhzflep.
#include <Windows.h>
#include <iostream>
#include <math.h>
#include <stdio.h>
using namespace std;
HBITMAP GetScreenBmp( HDC hdc) {
// Get screen dimensions
int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);
// Create compatible DC, create a compatible bitmap and copy the screen using BitBlt()
HDC hCaptureDC = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, nScreenWidth, nScreenHeight);
HGDIOBJ hOld = SelectObject(hCaptureDC, hBitmap);
BOOL bOK = BitBlt(hCaptureDC,0,0,nScreenWidth, nScreenHeight, hdc,0,0,SRCCOPY|CAPTUREBLT);
SelectObject(hCaptureDC, hOld); // always select the previously selected object once done
DeleteDC(hCaptureDC);
return hBitmap;
}
int main() {
HDC hdc = GetDC(0);
HBITMAP hBitmap = GetScreenBmp(hdc);
BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
// Get the BITMAPINFO structure from the bitmap
if(0 == GetDIBits(hdc, hBitmap, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error" << endl;
}
// create the bitmap buffer
BYTE* lpPixels = new BYTE[MyBMInfo.bmiHeader.biSizeImage];
// Better do this here - the original bitmap might have BI_BITFILEDS, which makes it
// necessary to read the color table - you might not want this.
MyBMInfo.bmiHeader.biCompression = BI_RGB;
// get the actual bitmap buffer
if(0 == GetDIBits(hdc, hBitmap, 0, MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error2" << endl;
}
for(int i = 0; i < 100; i++) {
cout << (int)lpPixels[i];
}
DeleteObject(hBitmap);
ReleaseDC(NULL, hdc);
delete[] lpPixels;
return 0;
}
Basically, you need to have drawn some pixels in order to get back a result other than 0.
At present, the 4th line of code in your main creates an empty (blank, 0-initialized) image. You then get information about the size of this image with your first call to GetDIBits. You then get the actual (blank) pixels with your second call to GetDIBits.
To fix, just load a bitmap file from disk into your hBitmap and select this bitmap into your hdcMem.
I.e, change
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, 1680, 1050);
to something like this.
HBITMAP hBitmap = (HBITMAP)LoadImage(NULL, "xpButton.bmp", IMAGE_BITMAP, 0,0, LR_LOADFROMFILE);
HBITMAP old = (HBITMAP) SelectObject(hdcMem, hBitmap);
(make sure you use a valid bmp file name. Mine exists in the same folder as the .cpp file, since this is the 'current' directory when you run via the IDE. If you wish to run via explorer, place another copy of the bmp in the same folder as your exe)
Here's the bmp I've used (which has been converted to a png after upload to SO):
And here's the first 10 iterations through the loop.
255
5
253
0
255
5
253
0
255
5
Note that the pixel at 0,0 has the colour of: rgb(253,5,255) and it's an 8bit image, so there's no alpha channel, hence it has the value 0. The pixels are stored as [BGRA], [BGRA], [BGRA], etc, etc.
I'll leave it to you to fix the (non-existant) clean-up section of your program. Windows will de-allocate the memory you've used here, but you absolutely should not get into the habit of not freeing any memory you've allocated. :)
Your code seems a bit confused. Too many snippets I guess :).
Still, you're quite close:
The first GetDIBits() call is in order to get the properties of the bitmap filled in, as the comment in your code suggests.
You are using an unnecessary MemDC for this - which is probably from a snippet that wants to do a BitBlt with the screen.
You then can use the filled in structure to get the actual bitmap pixels with the second GetDIBits() call, but what you're doing is replacing the properties with hard coded values again, making the first GetDIBits() call useless.
So: Drop the MemDC - you don't need it - and replace hdcMem with hdc in the first call to GetDIBits(), then remove all the statements that overwrite bmiHeader members after the first GetDIBits call and you should get your pixels.
Oh, and of course don't forget to call ReleaseDC()/DeleteObject() on the dc and bitmap and delete[] the buffer :)
Context: I'm trying to take a screenshot of another window to feed it into OpenCV. I found some code on the web that should be able to convert a BITMAP to something OpenCV can work with. Unfortunately I ran into some trouble.
Question: Why is the bmBits attribute/member always null? (I also tried with PrintWindow instead of BitBlt the result was the same)
#include <iostream>
#include <string>
#include <Windows.h>
int main(int argc, char* argv[])
{
std::wstring windowName = L"Calculator";
RECT rect;
HWND hwnd = FindWindow(NULL, windowName.c_str());
if (hwnd == NULL)
{
return 0;
}
GetClientRect(hwnd, &rect);
HDC hdcScreen = GetDC(NULL);
HDC hdc = CreateCompatibleDC(hdcScreen);
HBITMAP hbmp = CreateCompatibleBitmap(hdcScreen,
rect.right - rect.left, rect.bottom - rect.top);
SelectObject(hdc, hbmp);
PrintWindow(hwnd, hdc, PW_CLIENTONLY);
BITMAP bmp;
GetObject(hbmp, sizeof(BITMAP), &bmp);
return 0;
}
The bmBits member is non-null for DIB sections. For device-dependent bitmaps (such as the one you're creating), the bmBits is not set because the pixels are on the video card, not in main memory.
In your example, you need to change CreateCompatibleBitmap to CreateDIBSection if you want direct access to the bits.
Just for information.
When loading bitmap from file and want to use BITMAP .bmBits (for glTexImage2D, glDrawPixels):
LoadImage(NULL, "path_to.bmp", IMAGE_BITMAP, 0, 0,
LR_LOADFROMFILE);
u must specify flag LR_CREATEDIBSECTION
HBITMAP hBmp = NULL;
BITMAP BMp;
hBmp = (HBITMAP) LoadImage(NULL, "bitmap.bmp", IMAGE_BITMAP, 0, 0,
LR_LOADFROMFILE | LR_CREATEDIBSECTION);
GetObject(hBmp, sizeof(BMp), &BMp);
//BMp.bmBits now points to data
From GetObject documentation on MSDN. Please note the second paragraph.
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.
One thing which you could do is to look at the return value of GetObject. If 0 you know something has gone wrong. Something wrong with the parameters of the call.
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.