A while ago, I have created a CredentialProvider for Windows 7 that showed a custom tile image for the user. When I tested my CredentialProvider on Windows 10, I noticed that the tile image is not round as the usual Windows user image is, so I assumed, I have to provide my own round image with transparency. I tried to load a transparent PNG with the round shape and pass the corresponding HBITMAP in the ICredentialProviderCredentiall::GetBitmapValue() function. Unfortunately, instead of being transparent, the background of the PNG is white. Is there any way to show the actual transparency? Since the HBITMAP is drawn by LogonUI itself, I cannot modify the drawing behavior.
To create the HBITMAP out of my PNG resource, I use the following function:
HBITMAP LoadPNG(HINSTANCE hInst, int resourceId)
{
HGLOBAL hGlobal;
LPSTREAM pStream;
HBITMAP tBmp = NULL;
ULONG_PTR token = 0;
Gdiplus::GdiplusStartupInput input = NULL;
Gdiplus::GdiplusStartup(&token, &input, NULL);
if (token != 0)
{
HRSRC hRsrc = FindResource(hInst, MAKEINTRESOURCE(resourceId), TEXT("PNG"));
HGLOBAL hGlob1 = LoadResource(hInst, hRsrc);
int size = SizeofResource(hInst, hRsrc);
hGlobal = GlobalAlloc(GMEM_FIXED, size);
LPVOID resPtr = LockResource(hGlob1);
memcpy(hGlobal, resPtr, size);
FreeResource(hGlob1);
CreateStreamOnHGlobal(hGlobal, true, &pStream);
Gdiplus::Bitmap* bmp = new Gdiplus::Bitmap(pStream, false);
bmp->GetHBITMAP(Gdiplus::Color::Transparent, &tBmp);
Gdiplus::GdiplusShutdown(token);
}
return tBmp;
}
I tried also other values for the GetHBITMAP() background color parameter such as AlphaMask and AlphaShift, but these did not work either (instead, the white background turned black)
Is there any way to accomplish my goal?
The newest Credential Provider Technical Reference (which is not that easy to find on MSDN) actually tells what the issue with the tile image is:
In Windows 10, the selected User/V1/PLAP credential provider has an
image size of 192x192. The ones on the bottom left list is of 48x48.
Note LogonUI uses circular image for user and square image for V1/PLAP
according to the new design direction. The image size of V2 Credential
Provider tile under a selected user is 48x48.
If I read the documentation correctly then the challenge must be somehow to convince the LogonUI that its a User and not a V1/PLAP, I think this could be archieved returning a dummy user in the GetSerialization call.
Related
I am using this code to add a toolbar to the window with one button having a custom image:
HWND hToolbar = CreateWindow(TOOLBARCLASSNAME, NULL,WS_CHILD |
TBSTYLE_FLAT|TBSTYLE_AUTOSIZE |TBSTYLE_LIST|CCS_BOTTOM, 0, 0, 0, 0,
hwnd, NULL, ghInstance, NULL); //create the toolbar
SendMessage(hToolbar, WM_SETFONT, (WPARAM)hFontBold,
static_cast<LPARAM>(MAKELONG(TRUE, 0))); //set the font. there cannot be the problem
//↓↓↓↓↓**ILC_COLOR32 is specificied here but 32bit bmp is still not showing**//
auto hImagelist = ImageList_Create(32, 32,ILC_COLOR32|ILC_MASK,1, 0);
//↑↑↑↑↑**ILC_COLOR32 is specificied here but 32bit bmp is still not showing**//
HBITMAP bitmap = static_cast<HBITMAP>(ghInstance,
MAKEINTRESOURCE(ID_IMG_SPAWN),// <- ID_IMG_SPAWN is my custom resource
IMAGE_BITMAP, 32, 32, NULL));
ImageList_Add(hImagelist, bitmap, nullptr);
SendMessage(hToolbar, TB_SETIMAGELIST,static_cast<WPARAM>(0),(LPARAM)hImagelist);
In the code above, ID_IMG_SPAWN is the resource bmp image I imported to Visual Studio. However, Visual Studio threw an error saying it didn't recognize my bmp, and the bmp showed up blank when running the application.
Visual Studio told me my bmp wasn't recognized, see the below error:
When the app runs it looks as below:
I learned that Visual Studio hereby recognizes ONLY 24bit bmp.
So, I converted the bmp to 24bit and imported it again, changed ILC_COLOR32 to ILC_COLOR24, that really worked. No error and my image were shown on the button.
However, I lost my alpha channel. Because 24bit bitmap does not support an alpha channel, my image ended up having an ugly square background.
Try something like this (Note I used a "BINARY" resource.. maybe it will work with others too but not sure.. This code works with 32-bit bitmaps, alpha-transparent PNGs, and JPEG):
#include <windows.h>
#include <gdiplus.h>
HBITMAP LoadBitmapFromResource(DWORD ResourceID, bool transparent = true)
{
HANDLE hGlobal = NULL;
ULONG_PTR GDIToken = 0;
Gdiplus::Image* Img = NULL;
Gdiplus::GdiplusStartupInput GDIStartInput = NULL;
Gdiplus::GdiplusStartup(&GDIToken, &GDIStartInput, NULL);
HRSRC hResource = FindResource(NULL, MAKEINTRESOURCE(ResourceID), "BINARY");
if (!hResource) {return NULL;}
HGLOBAL hFileResource = LoadResource(NULL, hResource);
if (!hFileResource) {return NULL;}
LPVOID lpFile = LockResource(hFileResource);
if (!lpFile) {return NULL;}
DWORD dwSize = SizeofResource(NULL, hResource);
if (!dwSize) {return NULL;}
void* data = LockResource(hFileResource);
if (!data) {return NULL;}
IStream* pStream = NULL;
hGlobal = GlobalAlloc(GMEM_FIXED, dwSize);
memcpy(hGlobal, data, dwSize);
UnlockResource(hFileResource);
FreeResource(hFileResource);
if (CreateStreamOnHGlobal(hGlobal, true, &pStream) == S_OK)
{
Img = new Gdiplus::Image(pStream, false);
pStream->Release();
GlobalFree(hGlobal);
hGlobal = NULL;
HBITMAP hBitmap = NULL;
static_cast<Gdiplus::Bitmap*>(Img)->GetHBITMAP(transparent ? Gdiplus::Color::Transparent : Gdiplus::Color(0, 0, 0), &hBitmap);
delete Img;
Gdiplus::GdiplusShutdown(GdiImage::GDIToken);
GDIStartInput = NULL;
GDIToken = 0;
return hBitmap;
}
GlobalFree(hGlobal);
hGlobal = NULL;
Gdiplus::GdiplusShutdown(GdiImage::GDIToken);
GDIStartInput = NULL;
GDIToken = 0;
return NULL;
}
You will have to link against GDIPlus. It's not very nice to constantly startup and shutdown GDIPlus for every image you load.. so it's best to move that somewhere.. but other than that, everything should work just fine.
There are other ways without GDIPlus but it makes for a long post..
I learned that Visual Studio hereby recognizes ONLY 24bit bmp.
No, that's wrong. Visual Studio supports alpha-premultiplied 32-bit bitmaps.
32-bit bitmap has 8 bits for ALPHA, it's capable to make a smooth effect.
To show a 32-bit bitmap properly, you have to:
specify ILC_COLOR32
change the resource of ID_IMG_SPAWN to a 32-bit bitmap with premultiplied alpha.
create a DIB section to your bitmap when loading
(Win32's format requirement is very strict)
Q: How to create a DIB section to the bitmap?
A: Specify LR_CREATEDIBSECTION in the last parameter of LoadImage.
Explanation:
LoadImage((HINSTANCE)GetWindowLong(hwnd,GWL_HINSTANCE),MAKEINTRESOURCE(ID_IMG_SPAWN), IMAGE_BITMAP,32, 32,NULL)
This is your code of the LoadImage function. See the MSDN document of LoadImage, to create the DIB section, all you need is to specify LR_CREATEDIBSECTION in the last parameter of LoadImage.
Q: How to get a BMP with premultiplied alpha?
A: Pixelformer can help you convert your alpha-channeled file to a premultiplied-alpha BMP.
The steps are
Open your image (any format) in Pixelformer and choose Export from the menu
Select A8:R8:G8: B8 (32bpp) and Premultiplied Alpha, then click Ok.
Then you can save your BMP file! Import this BMP file to Visual Studio resources, replacing your previous 24-bit BMP.
Then, you don't need to use the ImageList_AddMasked (which makes the image sharp) anymore, because you already have a recognizable ALPHA in your 32-bit BMP. So, straight use ImageList_Add.
Okay, after the manipulations explained above your code should be this:
// Create the toolbar
HWND hToolbar = CreateWindow(TOOLBARCLASSNAME,NULL,
WS_CHILD | TBSTYLE_FLAT | TBSTYLE_AUTOSIZE | TBSTYLE_LIST | CCS_BOTTOM,
0, 0, 0, 0, hwnd, NULL, ghInstance, NULL);
// Set the font (this cannot be the problem)
SendMessage(hToolbar, WM_SETFONT, (WPARAM)hFontBold,
static_cast<LPARAM>(MAKELONG(TRUE, 0)));
auto hImagelist =
ImageList_Create(32, 32,ILC_COLOR32 /*DON'T NEED THE MASK. CHANGED TO ILC_COLOR32.*/, 1, 0);
HBITMAP bitmap = static_cast<HBITMAP>(LoadImage((HINSTANCE)GetWindowLong(hwnd,
GWL_HINSTANCE), MAKEINTRESOURCE(ID_IMG_SPAWN), IMAGE_BITMAP,
32, 32, LR_CREATEDIBSECTION /*THIS IS IMPORTANT*/ ));
ImageList_Add(hImagelist, bitmap, NULL);
SendMessage(hToolbar, TB_SETIMAGELIST, static_cast<WPARAM>(0), (LPARAM)hImagelist);
This worked fine as below.
These I answered above is well enough to solve this problem. You may wonder "What means DIB bitmaps?" "What is Premultiplied Alpha?". Those are the deep topics.
To learn DIB bitmaps and Premultiplied Alpha, see the links.
If you are using Visual Studio 2010 or higher (i guess), you can use PNG files. As stated here.
I have an MFC desktop application that generates a graphics image, and I want the user to be able to copy it to the clipboard as a bitmap. I use standard clipboard API routines and they have been working fine up to now. However, I have now activated GDI Scaling (via a manifest) so that the program can run (reasonably well) on HiDPI displays, and I find that the image placed on the clipboard is just the upper-left quadrant of the actual image.
This is presumably due to the internal scaling of the image - the display is running at 200%.
How do I copy the whole image?
The key is given in the answer to a previous question:
Saving Bitmaps on Windows 10 with GDI scaling active
but it took me some time to adapt that answer to my particular problem, so I thought I'd share in case it was helpful to others. (Disclaimer - I'm no expert, so there may be better ways...)
bool CopyRectToClipboard(CWnd *pW, CRect rctCopy)
{
if (!pW->OpenClipboard())
return false;
if (!EmptyClipboard())
return false;
CClientDC dc(pW);
CDC dcMem;
VERIFY(dcMem.CreateCompatibleDC(&dc));
CBitmap bmTrial; // need a trial bitmap to get GDI Scaled size
VERIFY(bmTrial.CreateCompatibleBitmap(&dc, rctCopy.Width(), rctCopy.Height()));
// see https://stackoverflow.com/questions/51169846/saving-bitmaps-on-windows-10-with-gdi-scaling-active
BITMAPINFO bi = {};
bi.bmiHeader.biSize = sizeof(bi);
int result = GetDIBits(dc.GetSafeHdc(), (HBITMAP)bmTrial.GetSafeHandle(), 0, 0, NULL, &bi, DIB_RGB_COLORS);
CBitmap bm;
VERIFY(bm.CreateCompatibleBitmap(&dc, bi.bmiHeader.biWidth, bi.bmiHeader.biHeight));
ASSERT(bm.m_hObject != NULL);
CBitmap* pbmOld = dcMem.SelectObject(&bm);
//dcMem.PatBlt(0, 0, bi.bmiHeader.biWidth, bi.bmiHeader.biHeight, WHITENESS); // legacy
VERIFY(dcMem.BitBlt(0, 0, bi.bmiHeader.biWidth, bi.bmiHeader.biHeight,
&dc, rctCopy.left - 1, rctCopy.top - 1, SRCCOPY));
HGDIOBJ hBM = bm.Detach();
VERIFY(::EmptyClipboard());
VERIFY(::SetClipboardData(CF_BITMAP, hBM));
VERIFY(::CloseClipboard());
dcMem.SelectObject(pbmOld);
dcMem.DeleteDC();
return true;
}
I have inherited an old-school MFC Windows CE program, and am having to make some modifications to it. As part of this I have to create a monochrome image with text on it, and both display it on a screen as well as send each row of the image to a printer one at a time.
I originally used a bitmap, and had success using DrawText() and getting a test string (Hello World) to display on the screen (this code is in Figure 1). However, I hit a wall at the stage where I am looking to extract the wrap data from the bitmap. What I am trying to get is an array with 1s or 0s representing black or white. I had first thought I would use GetBitmapBits() but unfortunately the code I am working with is so old that function is not supported yet. I thought I could get around this issue by using GetBitmap() and then accessing the bmBits parameter. However this appears to always be null which was confirmed when I found the following link: Why does GetObject return an BITMAP with null bmBits?.
My next attempt was to follow the advice in the link and use CreateDIBSection() instead of CreateCompatibleBitmap(). This seems like the right path, and I should have access to the data I want, but unfortunately I cannot get the DIB to display (code is in Figure 2). I suspect I am doing something wrong in creating the header of the DIB, but I cannot figure out what my mistake is.
If anyone has suggestions for a way to access the data in the bitmap, or can see what I am doing wrong with the DIB, I would greatly appreciate the help!
*** FIGURE 1: Code to create and display a bitmap
void CRunPage::OnPaint()
{
CPaintDC dc(this); // property page device context for painting
CBitmap mBmp; // CBitmap object for displaying built-in bitmaps
CDC mDCMem; // CDC object to handle built-in bitmap
int iWidth, iHeight; // dimension to draw on the screen
int icurLabel, // current label index of open print file
iLabelNum; // number of labels in open print file
LPBITMAPINFOHEADER pBMIH; // bitmap header object for current label
LPBYTE pImage; // bitmap data for current label
CSize size; // size of label
int PreviewLeft,PreviewTop,PreviewWidth,PreviewHeight;
CRect Rect;
BITMAP bm;
LPVOID bmBits=NULL;
// Calculate the preview area
PreviewLeft=5;
PreviewTop=5;
GetDlgItem(IDC_RUN_NEXT)->GetWindowRect(&Rect);
ScreenToClient(&Rect);
PreviewWidth=Rect.left-PreviewLeft*2;
GetDlgItem(IDC_RUN_WRAPTEXT)->GetWindowRect(&Rect);
ScreenToClient(&Rect);
PreviewHeight=Rect.top-PreviewTop*2;
CRect textRect;
CString testText(_T("Hello World"));
CBitmap * pOldBitmap;
CBrush whiteBrush, *pOldBrush;
CPen blackPen, *pOldPen;
mDCMem.CreateCompatibleDC(&dc);
mBmp.CreateCompatibleBitmap(&dc, PreviewWidth+PreviewLeft*2, PreviewHeight+PreviewTop*2);
//mBmp.CreateCompatibleBitmap(&dc, PreviewWidth, PreviewHeight);
pOldBitmap = mDCMem.SelectObject(&mBmp);
blackPen.CreatePen(PS_SOLID, 2, RGB(0, 0, 0));
whiteBrush.CreateSolidBrush(RGB(255,255,255));
textRect.SetRect(0,0,PreviewWidth, PreviewHeight);
// this means behind the text will be a white box w/ a black boarder
pOldBrush = mDCMem.SelectObject(&whiteBrush);
pOldPen = mDCMem.SelectObject(&blackPen);
//these commands draw on the memory-only context (mDCMem)
mDCMem.Rectangle(&textRect);
mDCMem.DrawText((LPCTSTR)testText, 11, &textRect, DT_CENTER|DT_VCENTER);
mDCMem.SelectObject(pOldBrush);
mDCMem.SelectObject(pOldPen);
dc.StretchBlt(PreviewLeft,PreviewTop, PreviewWidth, PreviewHeight, & mDCMem, 0, 0, PreviewWidth, PreviewHeight, SRCCOPY);
mDCMem.SelectObject(pOldBitmap);
}
*** FIGURE 2: Trying to use a DIB instead of a bitmap
void CRunPage::OnPaint()
{
CPaintDC dc(this); // property page device context for painting
CBitmap mBmp; // CBitmap object for displaying built-in bitmaps
CDC mDCMem; // CDC object to handle built-in bitmap
int iWidth, iHeight; // dimension to draw on the screen
int icurLabel, // current label index of open print file
iLabelNum; // number of labels in open print file
LPBITMAPINFOHEADER pBMIH; // bitmap header object for current label
LPBYTE pImage; // bitmap data for current label
CSize size; // size of label
int PreviewLeft,PreviewTop,PreviewWidth,PreviewHeight;
CRect Rect;
BITMAP bm;
// Calculate the preview area
PreviewLeft=5;
PreviewTop=5;
GetDlgItem(IDC_RUN_NEXT)->GetWindowRect(&Rect);
ScreenToClient(&Rect);
PreviewWidth=Rect.left-PreviewLeft*2;
GetDlgItem(IDC_RUN_WRAPTEXT)->GetWindowRect(&Rect);
ScreenToClient(&Rect);
PreviewHeight=Rect.top-PreviewTop*2;
CRect textRect;
CString testText(_T("Hello World"));
CBitmap * pOldBitmap;
CBrush whiteBrush, *pOldBrush;
CPen blackPen, *pOldPen;
LPBYTE pFWandImageMem=NULL, pImageMem=NULL, pTemp=NULL;
int i=0,j=0, buffSize=0, numBytesPerRow=0, bitmapWidthPix,bitmapHeightPix;
char *numBytesPerRowString;
char temp;
void ** ppvBits;
BITMAPINFOHEADER bmif;
BITMAPINFO bmi;
HBITMAP myDIB, myOldDIB;
mDCMem.CreateCompatibleDC(&dc);
//this rect is the area in which I can draw (its x,y location is set by BitBlt or StretchBlt
//mBmp.CreateCompatibleBitmap(&dc, PreviewWidth+PreviewLeft*2, PreviewHeight+PreviewTop*2);
bmif.biSize = sizeof(BITMAPINFOHEADER);
bmif.biWidth = PreviewWidth+PreviewLeft*2;
bmif.biHeight = -(PreviewHeight+PreviewTop*2);//- means top down (I think? I tried both ways and neither worked)
bmif.biPlanes = 1;
bmif.biBitCount = 1;
bmif.biCompression = BI_RGB; // no compression
bmif.biSizeImage = 0; // Size (bytes) if image - this can be set to 0 for uncompressed images
bmif.biXPelsPerMeter = 0;
bmif.biYPelsPerMeter = 0;
bmif.biClrUsed =0;
bmif.biClrImportant = 0;
bmi.bmiColors[0].rgbBlue=0;
bmi.bmiColors[0].rgbGreen=0;
bmi.bmiColors[0].rgbRed=0;
bmi.bmiColors[0].rgbReserved=0;
bmi.bmiColors[1].rgbBlue=255;
bmi.bmiColors[1].rgbGreen=255;
bmi.bmiColors[1].rgbRed=255;
bmi.bmiColors[1].rgbReserved=0;
bmi.bmiHeader=bmif;
myDIB = CreateDIBSection(dc.GetSafeHdc(), &bmi, DIB_RGB_COLORS, ppvBits, NULL, 0);
myOldDIB = (HBITMAP)mDCMem.SelectObject(myDIB);//SelectObject(mDCMem, myDIB);
blackPen.CreatePen(PS_SOLID, 2, RGB(0, 0, 0));
whiteBrush.CreateSolidBrush(RGB(255,255,255));
textRect.SetRect(0,0,PreviewWidth, PreviewHeight);
// this means behind the text will be a white box w/ a black boarder
pOldBrush = mDCMem.SelectObject(&whiteBrush);
pOldPen = mDCMem.SelectObject(&blackPen);
//these commands draw on the memory-only context (mDCMem)
mDCMem.Rectangle(&textRect);
mDCMem.DrawText((LPCTSTR)testText, 11, &textRect, DT_CENTER|DT_VCENTER);
mDCMem.SelectObject(pOldBrush);
mDCMem.SelectObject(pOldPen);
dc.StretchBlt(PreviewLeft,PreviewTop, PreviewWidth, PreviewHeight, & mDCMem, 0, 0, PreviewWidth, PreviewHeight, SRCCOPY);
mDCMem.SelectObject(myOldDIB);
}
So I made two minor changes to the DIB code, and it is displaying the image correctly now.
First, I changed the way I passed in my pointer to the CreateDIBSection():
void ** ppvBits;
to
LPBYTE pBits;
And then I had to change how I passed that into CreateDIBSection. I also explicitly casted the return of CreateDIBSection() to an HBITMAP:
myDIB = CreateDIBSection(dc.GetSafeHdc(), &bmi, DIB_RGB_COLORS, (void**)&pBits, NULL, 0);
to
myDIB = (HBITMAP) CreateDIBSection(dc.GetSafeHdc(), &bmi, DIB_RGB_COLORS, ppvBits, NULL, 0);
I have not had a chance to see if I can access the image data, but I am past the initial issues now. Thanks to anyone who looked at this, and if people know how to do the first (device dependent bitmap) method I would be interested to know.
(unmanaged C++)
I already succeeded drawing PNG files to a transparent layered window that I can drag around the desktop, but now my problem is drawing text on a transparent layered window
Here's my code and my attempt at drawing text in the middle, it's important to note that i'm using the screenDC instead of using the one in WM_PAINT messages
[edit]
updated code after the comments, now i'm just trying to write text on the bitmap before getting the HBITMAP version which i need to use
this time I'm using DrawString because textout() isn't GDI+, I hope DrawString really is GDI+ lol
still doesn't work though, wonder what i'm doing wrong
void Draw() // draws a frame on the layered window AND moves it based on x and y
{
HDC screenDC( NULL ); // grab screen
HDC sourceDC( CreateCompatibleDC(screenDC) );
POINT pos = {x,y}; // drawing location
POINT sourcePos = {0,0}; // top left of image
SIZE size = {100,100}; // 100x100 image
BLENDFUNCTION blendFunction = {0};
HBITMAP bufferBitmap = {0};
Bitmap* TheBitmap = crnimage; // crnimage was already loaded earlier
// ------------important part goes here, my attempt at drawing text ------------//
Gdiplus::Graphics Gx(TheBitmap);
// Font* myFont = new Font(sourceDC);
Font myFont(L"Arial", 16);
RectF therect;
therect.Height = 20;
therect.Width = 180;
therect.X = 0;
therect.Y = 0;
StringFormat format;
format.SetAlignment(StringAlignmentCenter);
format.GenericDefault();
Gdiplus::SolidBrush GxTextBrush(Gdiplus::Color(255, 255, 0,255));
WCHAR thetext[] = L"Sample Text";
int stats = Gx.DrawString(thetext, -1, &myFont, therect, &format, &GxTextBrush);
if(stats) // DrawString returns nonzero if there is an error
msgbox(stats);
stats = Gx.DrawRectangle(&Pen(Color::Red, 3), therect);
// the rectangle and text both draw fine now
// ------------important part goes here, my attempt at drawing text ------------//
TheBitmap->GetHBITMAP(0, &bufferBitmap);
HBITMAP oldBmpSelInDC;
oldBmpSelInDC = (HBITMAP)SelectObject(sourceDC, bufferBitmap);
// some alpha blending
blendFunction.BlendOp = AC_SRC_OVER;
blendFunction.SourceConstantAlpha = wndalpha;
blendFunction.AlphaFormat = AC_SRC_ALPHA;
COLORREF colorKey( RGB(255,0,255) );
DWORD flags( ULW_ALPHA);
UpdateLayeredWindow(hWnd, screenDC, &pos, & size, sourceDC, &sourcePos,
colorKey, &blendFunction, flags);
// release buffered image from memory
SelectObject(sourceDC, oldBmpSelInDC);
DeleteDC(sourceDC);
DeleteObject(bufferBitmap);
// finally release the screen
ReleaseDC(0, screenDC);
}
I've been trying to write text on my layered window for two days now, but from those attempts I know there are several ways I can go about doing this
(unfortunately I have no idea how exactly)
The usual option I see is drawing text on a bitmap, then rendering the bitmap itself
Use Gdi+ to load a bitmap
Create a Graphics object from the bitmap
Use DrawString to write text to the bitmap
Dispose of the Graphics object
Use the bitmap Save method to save the result to a file
Apparently one can also make a graphics object from a DC, then draw text on the DC, but again i have no clue as to how to do this
The overall approach looks right, but I think you've got some problems with the DrawString call. Check out the documentation (especially the sample) on MSDN.
Gx.DrawString(thetext, 4, NULL, therect, NULL, NULL)
The third, fifth, and sixth parameters (font, format, and brush) probably need to be specified. The documentation doesn't say that they are optional. Passing NULL for these is probably causing GDI+ to treat the call as a no-op.
The second parameter should not include the terminating L'\0' in the string. It's probably safest to use -1 if your string is always terminated.
I have an image data in a buffer(type - long) from a scanner which is 32 bit.
For example, buffer[0]'s corresponding pixel value is 952 which is [184, 3, 0, 0] <-[R,G,B,A];
I want to display/Paint/draw on to the screen; I am confused when i tried to read about displying bitmaps. I looked at win32 functions, CBitmap class, windows forms (picture box) etc I am hard to understand the general idea/appraoch for displaying this buffer data on to a application window.
I have constructed the BITMAPFILEHEADER AND BITMAPINFOHEADER; Has the pixel data in a buffer, (unsigned char *)vInBuff whose size is vImageSz;
//construct the BMP file Header
vBmfh.bfType = 19778;
vBmfh.bfSize = 54+vImageSz;//size of the whole image
vBmfh.bfReserved2 = 0;
vBmfh.bfReserved1 = 0;
vBmfh.bfOffBits = 54;//offset from where the pixel data can be found
//Construct the BMP info header
vBmih.biSize = 40;//size of header from this point
vBmih.biWidth = 1004;
vBmih.biHeight = 1002;
vBmih.biPlanes = 1;
vBmih.biCompression = BI_RGB;
vBmih.biSizeImage = vBmih.biWidth*vBmih.biHeight*4;
vBmih.biBitCount = 32;
vBmih.biClrUsed = 0;
vBmih.biClrUsed = 0;
1.What is that i should be doing next to display this?
2 What should i be using to display the 32bit bitmap? I see people using createwindows functions, windows forms, MFC etc;
3.I also understand that BitBlt,createDIBSection, OnPaint etc are being used? I am confused by these various functions and coding platforms? Please suggest me a simple approach.
4.How can i create a palette to display a 32 bit image?
Thanks
Raj
EDITED TRYING TO IMPLEMENT DAVE'S APPROACH, CAN SOMEBODY COMMENT ON MY IMPLEMTATION. I couldn't continue to the bitblt as i donot have two HDC, i donot know how to get this one? Any help please
DisplayDataToImageOnScreen(unsigned char* vInBuff, int vImageSz) // buffer with pixel data, Size of pixel data
{
unsigned char* vImageBuff = NULL;
HDC hdcMem=CreateCompatibleDC(NULL);
HBITMAP hBitmap = CreateDIBSection(hdcMem,
(BITMAPINFO*)&vBmih,
DIB_RGB_COLORS,
(void **)&vImageBuff,
NULL, 0);
GetDIBits(hdcMem,
hBitmap,
0,
1,
(void**)&vImageBuff,
(BITMAPINFO*)&vBmih,
DIB_RGB_COLORS);
memcpy(vImageBuff,vInBuff,vImageSz);
}
An alternative if you just want to plot it on screen is to use TinyPTC ( http://sourceforge.net/projects/tinyptc/files/ ). It's just 3 functions and very simple if you just want to plot some pixels.
EDIT: Seems like http://www.pixeltoaster.com is a continuation of TinyPTC, probably preffered.
If you have image's bytes already in a buffer you can use:
a CBitmap object (MFC) and the method CBitmap::CreateBitmapIndirect
or
win32 routine CreateBitmapIndirect.
Now you can use BitBlt to draw it on a DC. To get a window DC use GetDC.
There is no need to create a pallete for 32 bit images.
Here's a simplified approach you can try, broken down into steps:
BITMAPINFO bitmapinfo = { 0 };
bitmapinfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bitmapinfo.bmiHeader.biWidth = 1004;
bitmapinfo.bmiHeader.biHeight = -1002;
bitmapinfo.bmiHeader.biPlanes = 1;
bitmapinfo.bmiHeader.biCompression = BI_RGB;
HBITMAP hBitmap = CreateDIBSection(NULL,
&bitmapinfo,
DIB_RGB_COLORS,
(void **)&vImageBuff,
NULL,
0);
Now party on vImageBuff and then cache hBitmap somewhere so that within your wndproc you can then in the WM_PAINT handler:
select hBitmap into temp compatible HDC
call BitBlt(..., SRCCOPY) from the compatible HDC to the window's HDC. the other parameters should be obvious. don't try to stretch or do anything fancy at first.
remember to select the original dummy bitmap into the temp HDC before destroying it.
If you aren't seeing results try looping through vImageBuff and just set every pixel to RGB(255, 0, 0), or something like that, just to sanity check the rest of the logic.
If nothing is drawing make sure that the alpha component for each pixel is 255.
If you're getting a garbled image then you need to double-check pixelformat, stride, etc.
Here's a strategy you might like:
Create a bitmap with the same size as your scanned data, and the same format (use CreateDIBSection).
Use GetDIBits to get the base address of the pixel data.
Copy your data (from the scanner) to the address GetDIBits returns.
Now render your bitmap! (use BitBlt, or somesuch).
Regarding palettes- a 32bit image does not, generally, have an explicit palette - you'd need 16.7million (assuming 8bits of alpha) values in the palette. Generally the palette is assumed to be 8bits red, 8bits green, 8bits blue, as you've described above.