DrawIconEx leaving mask artifacts - c++

I'm extracting jumbo icons for any given path using IImageList and SHGetFileInfo. Once I have that, I then render the HICON into a HBITMAP using DrawIconEx for eventual rendering with GDI+ Bitmap and Graphics objects.
Now, this all works great, except that when I do the final rendering of the bitmap, the very left edge always has a black artifact on it. This is true for pretty much any icon I get, and is always the left edge.
Any ideas where the dark line could be coming from?
The code I'm using is roughly:
1. Extract Icon:
// Get the image list index of the icon
SHFILEINFO sfi;
if (!SHGetFileInfo(pszPath, 0, &sfi, sizeof(sfi), SHGFI_SYSICONINDEX)) return NULL;
// Get the jumbo image list
IImageList *piml;
if (FAILED(SHGetImageList(SHIL_JUMBO, IID_PPV_ARGS(&piml)))) return NULL;
// Extract an icon
HICON hicon;
piml->GetIcon(sfi.iIcon, ILD_SCALE|ILD_TRANSPARENT, &hicon);
return hicon;
2. Generate Bitmap
HDC hDC = GetDC(NULL);
HDC hMemDC = CreateCompatibleDC(hDC);
HBITMAP hMemBmp = CreateCompatibleBitmap(hDC, x, y);
HBITMAP hResultBmp = NULL;
HGDIOBJ hOrgBMP = SelectObject(hMemDC, hMemBmp);
HBRUSH hbr = CreateSolidBrush(bg);
RECT rr = { 0, 0, 256, 256 }; // jumbo icons
FillRect(hMemDC, &rr, hbr);
DeleteBrush(hbr);
DrawIconEx(hMemDC, 0, 0, hicon, size, size, 0, NULL, DI_NORMAL);
hResultBmp = hMemBmp;
hMemBmp = NULL;
SelectObject(hMemDC, hOrgBMP);
return hResultBitmap;
3. Render GDI+ Bitmap to "window bitmap":
Bitmap *b = ::New Bitmap(hResultBitmap, NULL);
Graphics graphics(hdc);
graphics.SetTextRenderingHint(TextRenderingHintClearTypeGridFit);
SolidBrush bgbrush(Color(255, 255, 255, 255));
Rect r(0, 0, hwnd_w, hwnd_h);
graphics.FillRectangle(&bgbrush, r);
graphics.SetInterpolationMode(InterpolationModeHighQualityBicubic);
Rect r(5, 5, 128, 128);
graphics.DrawImage(dpd->image_to_draw, r);

Wow, I spent another while last night playing with it. It's the ILD_SCALE in IImageList::GetIcon.
Get rid of that and it all works perfectly fine again. Go figure …
1. Extract Icon:
// Get the image list index of the icon
SHFILEINFO sfi;
if (!SHGetFileInfo(pszPath, 0, &sfi, sizeof(sfi), SHGFI_SYSICONINDEX)) return NULL;
// Get the jumbo image list
IImageList *piml;
if (FAILED(SHGetImageList(SHIL_JUMBO, IID_PPV_ARGS(&piml)))) return NULL;
// Extract an icon
HICON hicon;
piml->GetIcon(sfi.iIcon, ILD_TRANSPARENT, &hicon);
return hicon;

Related

How to show menu bitmaps with transparent background

I am using this code:
m_bmpSwap.LoadBitmap(IDB_BITMAP2);
pMnuPopup->SetMenuItemBitmaps(0, MF_BYPOSITION, &m_bmpSwap, &m_bmpSwap);
It looks like:
It was only a test image:
How exactly do I get my image to look as if it has a transparent background?
It is 24 bit image.
I have seen this but I can't work it out.
I adjusted to a 8 bit image with 192/192/192 as the background and loaded like this:
HBITMAP hBmp;
hBmp = (HBITMAP)::LoadImage(AfxGetResourceHandle(),
MAKEINTRESOURCE(IDB_BITMAP2),
IMAGE_BITMAP,
0, 0, // cx,cy
LR_CREATEDIBSECTION | LR_LOADMAP3DCOLORS);
m_bmpSwap.Attach(hBmp);
pMnuPopup->SetMenuItemBitmaps(0, MF_BYPOSITION, &m_bmpSwap, &m_bmpSwap);
That seems better if I am not running WindowsBlinds:
But when I put WindowsBlinds back on and show it again:
I am colourblind myself, but I can tell that the background actually matches the dialog background and not the menu colour background.
Is this the best I can do?
Just how can I have a 24 bit or 32 bit image as a menu bitmap?
Add LR_LOADTRANSPARENT flag as well as LR_LOADMAP3DCOLORS
This will work with 8-bit or 4-bit images (not tested with Windows blind)
Or you can manually change the background color
void swap_color(HBITMAP hbmp)
{
if(!hbmp)
return;
HDC hdc = ::GetDC(HWND_DESKTOP);
BITMAP bm;
GetObject(hbmp, sizeof(bm), &bm);
BITMAPINFO bi = { 0 };
bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bi.bmiHeader.biWidth = bm.bmWidth;
bi.bmiHeader.biHeight = bm.bmHeight;
bi.bmiHeader.biPlanes = 1;
bi.bmiHeader.biBitCount = 32;
std::vector<uint32_t> pixels(bm.bmWidth * bm.bmHeight);
GetDIBits(hdc, hbmp, 0, bm.bmHeight, &pixels[0], &bi, DIB_RGB_COLORS);
//assume that the color at (0,0) is the background color
uint32_t color_old = pixels[0];
//this is the new background color
uint32_t bk = GetSysColor(COLOR_MENU);
//swap RGB with BGR
uint32_t color_new = RGB(GetBValue(bk), GetGValue(bk), GetRValue(bk));
for (auto &pixel : pixels)
if(pixel == color_old)
pixel = color_new;
SetDIBits(hdc, hbmp, 0, bm.bmHeight, &pixels[0], &bi, DIB_RGB_COLORS);
::ReleaseDC(HWND_DESKTOP, hdc);
}
Usage:
CBitmap bmp;
bmp.LoadBitmap(IDB_BITMAP1);
swap_color(bmp);
menu.SetMenuItemBitmaps(0, MF_BYPOSITION, &bmp, &bmp);
I found this article. I replicate the made code here:
#define COLORREF2RGB(Color) (Color & 0xff00) | ((Color >> 16) & 0xff) \
| ((Color << 16) & 0xff0000)
//-------------------------------------------------------------------------------
// ReplaceColor
//
// Author : Dimitri Rochette drochette#coldcat.fr
// Specials Thanks to Joe Woodbury for his comments and code corrections
//
// Includes : Only <windows.h>
//
// hBmp : Source Bitmap
// cOldColor : Color to replace in hBmp
// cNewColor : Color used for replacement
// hBmpDC : DC of hBmp ( default NULL ) could be NULL if hBmp is not selected
//
// Retcode : HBITMAP of the modified bitmap or NULL for errors
//
//-------------------------------------------------------------------------------
HBITMAP ReplaceColor(HBITMAP hBmp,COLORREF cOldColor,COLORREF cNewColor,HDC hBmpDC)
{
HBITMAP RetBmp=NULL;
if (hBmp)
{
HDC BufferDC=CreateCompatibleDC(NULL); // DC for Source Bitmap
if (BufferDC)
{
HBITMAP hTmpBitmap = (HBITMAP) NULL;
if (hBmpDC)
if (hBmp == (HBITMAP)GetCurrentObject(hBmpDC, OBJ_BITMAP))
{
hTmpBitmap = CreateBitmap(1, 1, 1, 1, NULL);
SelectObject(hBmpDC, hTmpBitmap);
}
HGDIOBJ PreviousBufferObject=SelectObject(BufferDC,hBmp);
// here BufferDC contains the bitmap
HDC DirectDC=CreateCompatibleDC(NULL); // DC for working
if (DirectDC)
{
// Get bitmap size
BITMAP bm;
GetObject(hBmp, sizeof(bm), &bm);
// create a BITMAPINFO with minimal initilisation
// for the CreateDIBSection
BITMAPINFO RGB32BitsBITMAPINFO;
ZeroMemory(&RGB32BitsBITMAPINFO,sizeof(BITMAPINFO));
RGB32BitsBITMAPINFO.bmiHeader.biSize=sizeof(BITMAPINFOHEADER);
RGB32BitsBITMAPINFO.bmiHeader.biWidth=bm.bmWidth;
RGB32BitsBITMAPINFO.bmiHeader.biHeight=bm.bmHeight;
RGB32BitsBITMAPINFO.bmiHeader.biPlanes=1;
RGB32BitsBITMAPINFO.bmiHeader.biBitCount=32;
// pointer used for direct Bitmap pixels access
UINT * ptPixels;
HBITMAP DirectBitmap = CreateDIBSection(DirectDC,
(BITMAPINFO *)&RGB32BitsBITMAPINFO,
DIB_RGB_COLORS,
(void **)&ptPixels,
NULL, 0);
if (DirectBitmap)
{
// here DirectBitmap!=NULL so ptPixels!=NULL no need to test
HGDIOBJ PreviousObject=SelectObject(DirectDC, DirectBitmap);
BitBlt(DirectDC,0,0,
bm.bmWidth,bm.bmHeight,
BufferDC,0,0,SRCCOPY);
// here the DirectDC contains the bitmap
// Convert COLORREF to RGB (Invert RED and BLUE)
cOldColor=COLORREF2RGB(cOldColor);
cNewColor=COLORREF2RGB(cNewColor);
// After all the inits we can do the job : Replace Color
for (int i=((bm.bmWidth*bm.bmHeight)-1);i>=0;i--)
{
if (ptPixels[i]==cOldColor) ptPixels[i]=cNewColor;
}
// little clean up
// Don't delete the result of SelectObject because it's
// our modified bitmap (DirectBitmap)
SelectObject(DirectDC,PreviousObject);
// finish
RetBmp=DirectBitmap;
}
// clean up
DeleteDC(DirectDC);
}
if (hTmpBitmap)
{
SelectObject(hBmpDC, hBmp);
DeleteObject(hTmpBitmap);
}
SelectObject(BufferDC,PreviousBufferObject);
// BufferDC is now useless
DeleteDC(BufferDC);
}
}
return RetBmp;
}
Now, if I add a 24 bit bitmap to my project, and set the background as 71/71/71 and load it like this:
HBITMAP hBmp = (HBITMAP)::LoadImage(AfxGetResourceHandle(),
MAKEINTRESOURCE(IDB_BITMAP1),
IMAGE_BITMAP,
0, 0, // cx,cy
LR_LOADTRANSPARENT | LR_LOADMAP3DCOLORS);
HBITMAP hBmp2 = ReplaceColor(hBmp, RGB(71, 71, 71), GetSysColor(COLOR_MENU), NULL);
DeleteObject(hBmp);
m_bmpSwap.Attach(hBmp2);
pMnuPopup->SetMenuItemBitmaps(0, MF_BYPOSITION, &m_bmpSwap, &m_bmpSwap);
The result:

How to maintain transparency when writing text on a Windows System Tray icon from unmanaged C program

I have a MFC C++ (unmanaged) Windows application that uses a “standard” icon in the System Tray. This icon was created & edited using Visual Studio and is 32x32 pixels with only 4bit colour (according to VS's Resource Editor).
With Visual Studio, I also set a transparent background (shown as white in the “before” image).
I wish to dynamically change the icon by writing 2 digits (1-99) on top of it.
Using the code below (based on that in this question: How to draw text with transparency using GDI?) to superimpose “55” in yellow on the icon, it works except that the transparency disappears (it appears black in the “after” image and on the System Tray). My actual code differs very very slightly in that the font size (20), font name (Courier New), text colour (yellow - RGB(255, 255, 0)) and the numeric value (55) are run-time variables rather than fixed values.
Any suggestions on how to make the background remain transparent as far as the System Tray is concerned gratefully received.
These images have been captured using MS’s Snipping tool with the image open in MS Paint as a 32x32 icon wouldn't be very visible as-is.
Before Image:
After image:
Code:
void CreateNewIcon(HICON &hNewIcon, HICON hBackgroundIcon)
{
::DestroyIcon(hNewIcon);
// First create font
LOGFONT lf = { 0 };
lf.lfHeight = -20;
lf.lfWeight = FW_BOLD;
lf.lfOutPrecision = OUT_TT_PRECIS;
lf.lfQuality = CLEARTYPE_QUALITY;
wmemset(lf.lfFaceName, 0, LF_FACESIZE);
lstrcpy(lf.lfFaceName, L"Courier New");
HFONT hFont = ::CreateFontIndirect(&lf);
ICONINFO ii = { 0 };
::GetIconInfo(hBackgroundIcon, &ii);
BITMAP bm = { 0 };
::GetObject(ii.hbmColor, sizeof(bm), &bm);
SIZE szBmp = { bm.bmWidth, bm.bmHeight };
HDC hDc = ::GetDC(NULL);
HDC hMemDC = ::CreateCompatibleDC(hDc);
HGDIOBJ hOldBmp = ::SelectObject(hMemDC, ii.hbmColor);
HGDIOBJ hOldFont = ::SelectObject(hMemDC, hFont);
::SetBkMode(hMemDC, TRANSPARENT);
::SetTextColor(hMemDC, RGB(255, 255, 0));
::TextOut(hMemDC, 0, 8, L"55", 2);
::SelectObject(hMemDC, hOldFont);
::SelectObject(hMemDC, hOldBmp);
// We need a simple mask bitmap for the icon
HBITMAP hBmpMsk = ::CreateBitmap(szBmp.cx, szBmp.cy, 1, 1, NULL);
ICONINFO ii2 = { 0 };
ii2.fIcon = TRUE;
ii2.hbmColor = ii.hbmColor;
ii2.hbmMask = hBmpMsk;
// Create updated icon
hNewIcon = ::CreateIconIndirect(&ii2);
// Cleanup
::DeleteObject(hBmpMsk);
::DeleteDC(hMemDC);
::ReleaseDC(NULL, hDc);
::DeleteObject(ii.hbmColor);
::DeleteObject(ii.hbmMask);
::DeleteObject(hFont);
}
There are multiple issues with our code:
You are trying to draw cleartype-quality text over transparent icon part. But cleartype font rendering must be performed over opaque background because it needs to inspect background color. So you should switch to Anitialiased quality (or to not antialiased quality) or provide opaque background for your text.
When you create hBmpMsk you skip it's content initialization by supplying NULL for bits pointer, so resulting icon will actually have completely random transparency. You need to fill this mask bitmat appropriately.
Also you probably need to switch to higher bit depth because monochrome bitmap mask can't handle semitransparent parts of antialiased text.
update
I think you should draw cleartype text but with opaque background, then get text rectangle using something like GetTextExtentPoint32, then copy data from the original bitmap mask into hBmpMsk and then finally fill white (text) rectangle on it so the new icon will preserve transparency from original and has opaque text block.
Thanks for all the help from VTT without which I wouldn't have been able to get this far. This appears to work for me.
void CreateNewIcon(HICON &hNewIcon, HICON hBackgroundIcon)
{
::DestroyIcon(hNewIcon);
HDC hDc = ::GetDC(NULL);
HDC hMemDC = ::CreateCompatibleDC(hDc);
// Load up background icon
ICONINFO ii = { 0 };
::GetIconInfo(hBackgroundIcon, &ii);
HGDIOBJ hOldBmp = ::SelectObject(hMemDC, ii.hbmColor);
// Create font
LOGFONT lf = { 0 };
lf.lfHeight = -20;
lf.lfWeight = FW_BOLD;
lf.lfOutPrecision = OUT_TT_PRECIS;
lf.lfQuality = ANTIALIASED_QUALITY;
wmemset(lf.lfFaceName, 0, LF_FACESIZE);
lstrcpy(lf.lfFaceName, L"Courier New");
HFONT hFont = ::CreateFontIndirect(&lf);
HGDIOBJ hOldFont = ::SelectObject(hMemDC, hFont);
// Write text
::SetBkMode(hMemDC, TRANSPARENT);
::SetTextColor(hMemDC, RGB(255, 255, 0));
::TextOut(hMemDC, 0, 8, L"55", 2);
// Set up mask
HDC hMaskDC = ::CreateCompatibleDC(hDc);
HGDIOBJ hOldMaskBmp = ::SelectObject(hMaskDC, ii.hbmMask);
// Also write text on here
HGDIOBJ hOldMaskFont = ::SelectObject(hMaskDC, hFont);
::SetBkMode(hMaskDC, TRANSPARENT);
::SetTextColor(hMaskDC, RGB(255, 255, 0));
::TextOut(hMaskDC, 0, 8, L"55", 2);
// Get handle to create mask bitmap
HBITMAP hMaskBmp = (HBITMAP)::SelectObject(hMaskDC, hOldMaskBmp);
// Use new icon bitmap with text and new mask bitmap with text
ICONINFO ii2 = { 0 };
ii2.fIcon = TRUE;
ii2.hbmMask = hMaskBmp;
ii2.hbmColor = ii.hbmColor;
// Create updated icon
hNewIcon = ::CreateIconIndirect(&ii2);
// Cleanup bitmap mask
::DeleteObject(hMaskBmp);
::DeleteDC(hMaskDC);
// Cleanup font
::SelectObject(hMaskDC, hOldMaskFont);
::SelectObject(hMemDC, hOldFont);
::DeleteObject(hFont);
// Release background bitmap
::SelectObject(hMemDC, hOldBmp);
// Delete background icon bitmap info
::DeleteObject(ii.hbmColor);
::DeleteObject(ii.hbmMask);
::DeleteDC(hMemDC);
::ReleaseDC(NULL, hDc);
}

How to draw text with transparency using GDI?

My goal is to dynamically put some arbitrary text into an HICON image (at runtime.) I'm using the following code:
//Error checks are omitted for brevity
//First create font
LOGFONT lf = {0};
lf.lfHeight = -58;
lf.lfWeight = FW_NORMAL;
lf.lfOutPrecision = OUT_TT_PRECIS; //Use TrueType fonts for anti-alliasing
lf.lfQuality = CLEARTYPE_QUALITY;
lstrcpy(lf.lfFaceName, L"Segoe UI");
HFONT hFont = ::CreateFontIndirect(&lf);
//HICON hIcon = original icon to use as a source
//I'm using a large 256x256 pixel icon
hIcon = (HICON)::LoadImage(theApp.m_hInstance, MAKEINTRESOURCE(IDI_ICON_GREEN_DIAMOND), IMAGE_ICON, 256, 256, LR_DEFAULTCOLOR);
ICONINFO ii = {0};
::GetIconInfo(hIcon, &ii);
BITMAP bm = {0};
::GetObject(ii.hbmColor, sizeof(bm), &bm);
SIZE szBmp = {bm.bmWidth, bm.bmHeight};
HDC hDc = ::GetDC(hWnd);
HDC hMemDC = ::CreateCompatibleDC(hDc);
HGDIOBJ hOldBmp = ::SelectObject(hMemDC, ii.hbmColor);
HGDIOBJ hOldFont = ::SelectObject(hMemDC, hFont);
::SetBkMode(hMemDC, TRANSPARENT);
::SetTextColor(hMemDC, RGB(255, 0, 0)); //Red text
//Draw text
//NOTE that DrawText API behaves in a similar way
::TextOut(hMemDC, 0, 0, L"Hello", 5);
::SelectObject(hMemDC, hOldFont);
::SelectObject(hMemDC, hOldBmp);
//We need a simple mask bitmap for the icon
HBITMAP hBmpMsk = ::CreateBitmap(szBmp.cx, szBmp.cy, 1, 1, NULL);
ICONINFO ii2 = {0};
ii2.fIcon = TRUE;
ii2.hbmColor = ii.hbmColor;
ii2.hbmMask = hBmpMsk;
//Create updated icon
HICON hIcon2 = ::CreateIconIndirect(&ii2);
//Cleanup
::DeleteObject(hBmpMsk);
::DeleteDC(hMemDC);
::ReleaseDC(hWnd, hDc);
::DeleteObject(ii.hbmColor);
::DeleteObject(ii.hbmMask);
::DeleteObject(hFont);
and then I can display the icon in my window from OnPaint() handler (so that I can see how it turns out) as such:
::DrawIconEx(dc.GetSafeHdc(), 0, 0,
hIcon2,
256, 256, NULL,
::GetSysColorBrush(COLOR_BTNFACE),
DI_NORMAL);
So here's what I get:
To see what's going on pixel-wise in my hIcon2 I called GetDIBits on its ii.hbmColor from the code above. The resulting pixel array where my word "Hello" was supposed to be shown looked like this:
The pixels are encoded as BGRA in that memory dump, so the 4th byte in each DWORD stands for transparency: 0=transparent, FF=opaque. But in this case TextOut doesn't fill out transparency, or leaves it as 0, which is interpreted as "fully transparent." Instead it seems to pre-multiply it into the RGB colors themselves.
Note that if I keep looking further down the same bitmap, where the green diamond begins, the image pixels seem to have transparency bytes set correctly:
Any idea how to draw text so that the API could set those transparency bytes?
EDIT: As was suggested below I tried the following GDI+ method:
HGDIOBJ hOldBmp = ::SelectObject(hMemDC, ii.hbmColor);
Graphics grpx(hMemDC);
RectF rcfTxt(0.0f, 0.0f, (REAL)szBmp.cx, (REAL)szBmp.cy);
Font gdiFont(L"Segoe UI", 58.0f, FontStyleRegular, UnitPixel);
SolidBrush gdiBrush(Color(255, 0, 0));
StringFormat gdiSF;
gdiSF.SetAlignment(StringAlignmentNear);
gdiSF.SetFormatFlags(StringFormatFlagsNoWrap);
gdiSF.SetHotkeyPrefix(HotkeyPrefixNone);
//The reason I was using GDI was because I was setting
//spacing between letters using SetTextCharacterExtra()
//Unfortunately with GDI+ this does not work!
HDC hTmpDC = grpx.GetHDC();
::SetTextCharacterExtra(hTmpDC, -4); //This doesn't do anything!
grpx.ReleaseHDC(hTmpDC);
grpx.DrawString(L"Hello", 5, &gdiFont, rcfTxt, &gdiSF, &gdiBrush);
::SelectObject(hMemDC, hOldBmp);
and besides not being able to set character spacing (which I could with GDI using SetTextCharacterExtra) here's what I got (slightly enlarged for visibility):
So clearly still an issue with transparency.
Taken from an old post by Microsoft MVP Mike D Sutton here.
When you create a DC it initially has default 'stock' objects selected
into it, including the stock 1*1*1 Bitmap. Since there is a Bitmap
already selected into the DC when you call DrawText() it will still
try and render to it even though pretty much everything (apart from
one pixel) will be clipped.
What you need to do is to create a Bitmap,
either DDB or DIBSection, and select that into your DC before drawing
to it.
First though you need to find the size of your Bitmap since you
want it large enough to display your text in, so for that you use the
DrawText() call again on the initial DC but include the DT_CALCRECT
flag. What this does is rather than drawing anything it simply
measures how large the text is and dumps that into the RECT you pass
the call. From here you can go ahead and create your DIBSection using
those dimensions and select it into your DC. Finally perform your
existing DrawText ()call (you may also want to use SetBkMode/Color())
which will render the text to the DIBSection from which you can get at
the data.
This seems to work pretty well here:
HBITMAP CreateAlphaTextBitmap(LPCSTR inText, HFONT inFont, COLORREF inColour) {
int TextLength = (int)strlen(inText);
if (TextLength <= 0) return NULL;
// Create DC and select font into it
HDC hTextDC = CreateCompatibleDC(NULL);
HFONT hOldFont = (HFONT)SelectObject(hTextDC, inFont);
HBITMAP hMyDIB = NULL;
// Get text area
RECT TextArea = {0, 0, 0, 0};
DrawText(hTextDC, inText, TextLength, &TextArea, DT_CALCRECT);
if ((TextArea.right > TextArea.left) && (TextArea.bottom > TextArea.top)) {
BITMAPINFOHEADER BMIH;
memset(&BMIH, 0x0, sizeof(BITMAPINFOHEADER));
void *pvBits = NULL;
// Specify DIB setup
BMIH.biSize = sizeof(BMIH);
BMIH.biWidth = TextArea.right - TextArea.left;
BMIH.biHeight = TextArea.bottom - TextArea.top;
BMIH.biPlanes = 1;
BMIH.biBitCount = 32;
BMIH.biCompression = BI_RGB;
// Create and select DIB into DC
hMyDIB = CreateDIBSection(hTextDC, (LPBITMAPINFO)&BMIH, 0, (LPVOID*)&pvBits, NULL, 0);
HBITMAP hOldBMP = (HBITMAP)SelectObject(hTextDC, hMyDIB);
if (hOldBMP != NULL) {
// Set up DC properties
SetTextColor(hTextDC, 0x00FFFFFF);
SetBkColor(hTextDC, 0x00000000);
SetBkMode(hTextDC, OPAQUE);
// Draw text to buffer
DrawText(hTextDC, inText, TextLength, &TextArea, DT_NOCLIP);
BYTE* DataPtr = (BYTE*)pvBits;
BYTE FillR = GetRValue(inColour);
BYTE FillG = GetGValue(inColour);
BYTE FillB = GetBValue(inColour);
BYTE ThisA;
for (int LoopY = 0; LoopY < BMIH.biHeight; LoopY++) {
for (int LoopX = 0; LoopX < BMIH.biWidth; LoopX++) {
ThisA = *DataPtr; // Move alpha and pre-multiply with RGB
*DataPtr++ = (FillB * ThisA) >> 8;
*DataPtr++ = (FillG * ThisA) >> 8;
*DataPtr++ = (FillR * ThisA) >> 8;
*DataPtr++ = ThisA; // Set Alpha
}
}
// De-select bitmap
SelectObject(hTextDC, hOldBMP);
}
}
// De-select font and destroy temp DC
SelectObject(hTextDC, hOldFont);
DeleteDC(hTextDC);
// Return DIBSection
return hMyDIB;
}
If you need an example of how to call it then try something like this
(inDC is the DC to render to):
void TestAlphaText(HDC inDC, int inX, int inY) {
const char *DemoText = "Hello World!\0";
RECT TextArea = {0, 0, 0, 0};
HFONT TempFont = CreateFont(50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Arial\0");
HBITMAP MyBMP = CreateAlphaTextBitmap(DemoText, TempFont, 0xFF);
DeleteObject(TempFont);
if (MyBMP) { // Create temporary DC and select new Bitmap into it
HDC hTempDC = CreateCompatibleDC(inDC);
HBITMAP hOldBMP = (HBITMAP)SelectObject(hTempDC, MyBMP);
if (hOldBMP) {
BITMAP BMInf; // Get Bitmap image size
GetObject(MyBMP, sizeof(BITMAP), &BMInf);
// Fill blend function and blend new text to window
BLENDFUNCTION bf;
bf.BlendOp = AC_SRC_OVER;
bf.BlendFlags = 0;
bf.SourceConstantAlpha = 0x80;
bf.AlphaFormat = AC_SRC_ALPHA;
AlphaBlend(inDC, inX, inY, BMInf.bmWidth, BMInf.bmHeight,
hTempDC, 0, 0, BMInf.bmWidth, BMInf.bmHeight, bf);
// Clean up
SelectObject(hTempDC, hOldBMP);
DeleteObject(MyBMP);
DeleteDC(hTempDC);
}
}
}
All credit to answer and code go to original posters on that forum, I've simply reposted it so that this answer will be valid if the links die.
This reply is coming almost 3 years after the question was posted, but people still consult these things long into the future. So I'll explain what's happening.
DrawText (and other GDI text functions) will work on a transparent bitmap. The text is not coming out black even though it displays that way. The alpha channel is set to 0 on all pixels the text draws to, overriding whatever alpha you had set previously. If you set an alpha value in SetTextColor the text will render all black. If you're feeling ambitious you can run through pixel by pixel and target anything not your fill color (which requires a single fill color) but the problem then becomes one of the nature of ClearType being overridden and all alphas are set to whatever you set them to. The text ends up looking very funky. If you use a constant alpha for your background fill you can simply do a blanket run across the entire bitmap's bits after the text is drawn and reset all the alpha values. Since you have to read a byte to determine if it's background or not, you might as well just set every pixel's alpha to whatever the standard alpha is for that image and bypass the slow compares. This works reasonably well and I've found it to be very acceptable. In this day and age, MS should have taken care of this long ago but it's not to be.
https://learn.microsoft.com/en-us/windows/win32/gdiplus/-gdiplus-antialiasing-with-text-use
Gdiplus::Bitmap bmp( your_Width, your_Height, PixelFormat64bppARGB);
//PixelFormat64bppARGB ARGB needed
FontFamily fontFamily(L"Arial");
Font font(&fontFamily, 29, FontStyleRegular, UnitPoint);
Gdiplus::RectF rectF(00.0f, 10.0f, your_Width, your_Height);
StringFormat stringFormat;
SolidBrush solidBrush(Color(63, 0, 0, 255));
stringFormat.SetAlignment(StringAlignmentCenter);
//solidBrush Color(63, 0, 0, 255) ARGB neede
graphics.SetTextRenderingHint(TextRenderingHintAntiAlias);
graphics.DrawString("your_text", -1, &font, rectF, &stringFormat, &solidBrush);
//TextRenderingHintAntiAlias this needed

GDI+ DC in memory always monochrome

Working in mingw, having a terrible time creating a color DC in memory. For instance, in the following code snippet, as written, "foo_scratch.bmp" is a monochrome version of the
image (from an EMR_STRETCHDIBITS record). If instead aDC is omitted and srcDC uses the CreateDC directly, then that file has a color image.
Gdiplus::Bitmap *pbmp = NULL;
BITMAPINFO *pbitmapinfo = (BITMAPINFO *)((char *)lpEMFR + pEmr->offBmiSrc);
void *pBitsInMem = (char *)lpEMFR + pEmr->offBitsSrc;
HBITMAP hbmsrc;
HDC aDC = CreateDC("DISPLAY", "", NULL, NULL);
HDC srcDC = CreateCompatibleDC(aDC);
hbmsrc = CreateDIBitmap(
srcDC,
&(pbitmapinfo->bmiHeader),
CBM_INIT,
pBitsInMem,
pbitmapinfo,
DIB_RGB_COLORS);
if(hbmsrc){
CLSID pngClsid;
GetEncoderClsid(L"image/bmp", &pngClsid);
pbmp = Gdiplus::Bitmap::FromHBITMAP(hbmsrc,NULL);
pbmp->Save(L"C:\\Temp\\foo_scratch.bmp",&pngClsid, NULL);
This all comes to a head later when two images (hbmdst, hbmsrc) need to be put together with a bitblt operation. At present the best I have managed is monochrome. At worst the image is solid black. In this snippet the ROP has been hard coded to SRCCOPY, and I still have not succeeded in just copying the image from one HBITMAP to another. Very frustrating!
HDC dstDC = CreateCompatibleDC(aDC);
HBITMAP hbmdOld = (HBITMAP) SelectObject(dstDC, hbmdst);
HBITMAP hbmsOld = (HBITMAP) SelectObject(srcDC, hbmsrc);
GetObject(hbmsrc, sizeof(bm), &bm);
BitBlt(dstDC, 0, 0, bm.bmWidth, bm.bmHeight, srcDC, 0, 0, SRCCOPY);
SelectObject(srcDC, hbmsOld);
SelectObject(dstDC, hbmdOld);
(void) DeleteDC(dstDC);
pbmp = Gdiplus::Bitmap::FromHBITMAP(hbmdst,NULL);
pbmp->Save(L"C:\\Temp\\scratch.bmp",&pngClsid, NULL);
What am I doing wrong?
Thanks
Figured it out - wherever a bitmap is created have to use the DC directly associated with the display (or other device), not the "compatible" DC derived from the first DC.

How to convert HICON to HBITMAP in VC++?

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.