I can't seem to get the CBitmap to actually apear on the screen... Here's the code in OnPaint:
CRect frm;
GetClientRect(frm);
CClientDC dc(this);
//dc.FillSolidRect(CRect(0, 0, 1000, 1000), RGB(255, 255, 255));
CDC dcMem;
dcMem.CreateCompatibleDC(&dc);
CBitmap* cache = dcMem.SelectObject(&components.icon.bmp);
dc.BitBlt(0, 0, 55, 55, &dcMem, 0, 0, SRCCOPY);
dc.SelectObject(cache);
The definition of components.icon.bmp is...
components.icon.bmp.LoadBitmap(BMP_BOARDER);
BITMAP icon;
components.icon.bmp.GetBitmap(&icon);
There shouldn't be problem here. The Bitmap is a 32bit alpha bitmap and LoadBitmap returned TRUE.
It doesn't work with 24 bit either.
---- Got it! Problem with my resources
This code seems good to me but there are still many things that can be wrong. Test your code to know where the problem is:
- If you draw anything else (a rectangle for instance) does it appears on the frame window?
- Try to save the bmp to a file and see if it's ok.
- Try to convert the bmp to 24bits using a tool and see if it works.
Once you know where the problem is you'll be able to focus on the problem.
Probably you won't be able to draw a 32bits bmp using GDI but you should get something (a black square at least). Anyway, if you need to draw 32bits alpha-channel bmps using GDI you have to pre-multiply the image and use AlphaBlend method instead of BitBlt.
Related
When I bitblt onto my transparent window, a bmp smaller than the client area, it draws a fussy surrounding area instead of transparent like the set colorkey from:
SetLayeredWindowAttributes(hwnd, RGB(0,255,0), 120, LWA_COLORKEY | LWA_ALPHA); //colorkey & win alpha
The blit looks like this:
The candle-like test image makes its own area transparent like it should, but the surrounding client area gets grayed out according to the window-alpha value (120). Any ideas how to fix this? I've tried:
SetBkColor(hdc, crKey); and generating a background with
FillRect(background_hdc, &background_rect, hbrush); and blitting that first
Where neither work.
I have the feeling this should be alot easier than I'm making it out to be, and I still feel something like SetBkColor(hdc,crKey); should do the trick, but it doesnt. Maybe there is a similar command that does that I'm looking for?
Isnt it funny how you solve the problem just after you formulate it properly?
Obviously the hbrBackground in the WNDCLASSEX wc;
defines the background of the window. So by setting the brush background when registering the window like so:
wc.hbrBackground=CreateSolidBrush(RGB(240, 20, 120)); //COLORREF==crKey
it gets crKey cancelled out during the blit along with the bmps crKey color. Thanks.
I need a way to display a PNG image with transparent background on a background with gradient color.
I have tried this:
CImage img;
CBitmap bmp;
img.Load(_T(".\\res\\foo.png"));
bmp.Attach(img.Detach());
CDC dcStatus;
dcStatus.CreateCompatibleDC(&dc);
dcStatus.SelectObject(&bmp);
dcStatus.SetBkColor(TRANSPARENT);
dc.BitBlt(rectText.left + 250, rectText.top, 14, 14, &dcStatus, 0, 0, SRCCOPY);
bmp.DeleteObject();
but foo.png gets black background wherever it is transparent in original image.
I did try to do a new bitmap that was painted with transparent color and did all possible operations on it, but that didn't help. Sample of one permutation:
CImage img;
CBitmap bmp;
img.Load(_T(".\\res\\foo.png"));
bmp.Attach(img.Detach());
CBitmap bmpMaska;
bmpMaska.CreateBitmap(14, 14, 1, 1, NULL);
CDC dcStatus;
dcStatus.CreateCompatibleDC(&dc);
dcStatus.SelectObject(&bmp);
CDC dcMaska;
dcMaska.CreateCompatibleDC(&dc);
dcMaska.SelectObject(&bmpMaska);
dcMaska.SetBkColor(dcStatus.GetPixel(0, 0));
//TODO: Bitmap ni transparent
dc.BitBlt(rectText.left + 250, rectText.top, 14, 14, &dcMaska, 0, 0, SRCCOPY);
dc.BitBlt(rectText.left + 250, rectText.top, 14, 14, &dcStatus, 0, 0, SRCAND);
bmp.DeleteObject();
bmpMaska.DeleteObject();
This did not do the trick. Either, there was all black square on the screen, or the result was the same as original.
I have also checked AlphaBlend API, but my code must be pure MFC + C++ witthout any additional APIs.
[Edit]: Company policy is as little APIs as possible. The code is supposed to run on embedded windows systems in real time.
[Edit 2]: I am not bound to PNG image format, meaning, anything that will display as transparent, goes.
Please, tell me what am I doing wrong?
Convert the png to a 32 bit bmp file. Google 'AlphaConv' and use that. PNG's are a PITA to work with - several API's claim to support them but actually don't, or only partially, or only on some platforms etc.
Load your 32-bit bmp using CBitmap::LoadBitmap (from resources - this is by far the easiest)
Then use CDC::AlphaBlend() to draw your bitmap. TransparentBlt() doesn't work with an alpha channel - it's just either draw the pixel or not. AlphaBlend is part of the win32 API, and you could still investigate CImage::AlphaBlend if you'd like, but that has a bug somewhere (I forgot what exactly) so I always use the raw ::AlphaBlend.
But beware - you need to premultipy the alpha channel for correct display. See my answer on How to draw 32-bit alpha channel bitmaps? .
No variation of what you described will work. You need another API to get this to work. Or, you could use GetDIBits and do your own version of ::AlphaBlend() :)
Based on what you're asking for (simply some set of pixels being transparent) it's probably easiest to use a 24- or 32-bit BMP, and simply pick a color to treat as transparent. Pre-process your picture to take any pixel that precisely matches your transparent color and increase change the least significant bit of one of the channels.
Given 8 bits per channel, this won't normally cause a visible change. Then draw the pixels you want transparent in one exact color. This is easy to do in something like a paint program.
You can then draw that to your DC using TransparentBlt. That lets you specify the color you want to treat as transparent.
i have an issue with a fix i made to allow a flood filled object be printed...
so, the full story is we were using the windows GDI FloodFill function, which we noticed doesnt work on printers, so what i found on the inet, was to create a memory DC, compatible with the printer DC, and make all my drawing operations on the memory DC, and then BitBlt it all at once to the printer DC (i had to change to use a recursive, color replacment flood fill function too, since the memory DC only allows what the main DC did)
the problem is the memory DC seems to be a pixel or two bigger on the x and y, but i dont know what to do, when i get the selected bitmap from the memory DC, it shows it to be the correct size, i would like to use StretchBlt, but the values i have access to use as params for StretchBlt, make it no different than calling BitBlt
let me know if you need more info...
thanks in advance!!!
heres my code:
HDC hMemPrnDC = CreateCompatibleDC (hPrnDC);
HBITMAP hBitmap = CreateCompatibleBitmap (hPrnDC, iWidthLP, iHeightLP);
HBITMAP hOldBitmap = SelectBitmap (hMemPrnDC, hBitmap);
// paint the whole memory DC with the window color
HBRUSH hBrush = CreateSolidBrush (GetSysColor (COLOR_WINDOW));
RECT rect;
// add one to right and bottom, FillRect doesnt include the right and bottom edges
SetRect (&rect, 0, 0, iWidthLP + 1, iHeightLP + 1);
// NOTE: im doing this cause it starts out as all black
FillRect (hMemPrnDC, &rect, hBrush);
// delete object
DeleteBrush (hBrush);
//
// do all my MoveToEx, LineTo, Ellipse, Arc, TextOut,
// SetPixel, etc calls on hMemPrnDC here
//
// copy all the memory DC drawing data to the printer DC
BitBlt (hPrnDC, 0, 0, iWidthLP, iHeightLP, hMemPrnDC, 0, 0, SRCCOPY);
// select old bitmap, and clean up objects
SelectBitmap (hMemPrnDC, hOldBitmap);
DeleteBitmap (hBitmap);
DeleteDC (hMemPrnDC);
hMemPrnDC = NULL;
UPDATE (Sept 5):
here is a link to a PDF print where I draw straight to the printer DC:
hPrnDC.pdf
and here is the same but I draw to the memory DC then BitBlt it to the printer DC:
hMemPrnDC.pdf
now, I did enable my recursive flood fill function on the second, to show an example of what we are trying to achieve, it does the same without it, so that is not an issue
as you can see, the bottom and right edge are cut off, I'm also concerned about the differences in font & line weight between the two, but not as much as the sizing mismatch
NOTE: the filename printed at the top doesn't go through the memory DC, that is always drawn straight to the printer DC
I found a solution to my problem, more of a work-around, but it achieved the desired results...
I only used the memory DC as a go between on the items that needed the recursive flood fill (GetPixel and SetPixel), so I draw them first to the memory DC, copy it all over to the printer DC and then draw everything else straight to the printer DC, seems to work just fine
thanks for the help!
I am new to MFC. Now I have the following question:
I have a large-size picture (e.g. size of 2000*2000) display in a small-size window (e.g. size of 640*480). No wonder that the picture cannot show itself fully without zooming out. I know I can save the original picture without losing any pixel if the picture can fit into the window, however, I cannot do this at this time:
CClientDC SHDC(this); //"this" is a CMDIChildWnd derived class
CDC memDC;
CRect rect;
GetClientRect(&rect);
memDC.CreateCompatibleDC(&SHDC);
CBitmap bm;
int uWidth = rect.Width();
int uHeight = rect.Height();
bm.CreateCompatibleBitmap(&SHDC, uWidth, uHeight);
CBitmap *pOld = memDC.SelectObject(&bm);
memDC.BitBlt(0, 0, uWidth, uHeight, &SHDC, 0, 0, SRCCOPY);
......
The saved picture only show the client area, but I would like to get all of the picture saved.
Anyone who can help me? Thanks in advance.
Xi
Instead of BitBlt try StretchBlt. It'll handle the shrinking for you.
The StretchBlt function copies a bitmap from a source rectangle into a
destination rectangle, stretching or compressing the bitmap to fit the
dimensions of the destination rectangle, if necessary. The system
stretches or compresses the bitmap according to the stretching mode
currently set in the destination device context.
If you want higher quality stretching/shrinking look at GDI+. There's a variety of interpolation modes you can use. More info here:
http://msdn.microsoft.com/en-us/library/k0fsyd4e.aspx
I'm trying to do some double buffering in an MFC application and trying to draw on the memory DC with GDI+. However, although I called CreateCompatibleDC(), I'm only getting a monochrome image. Here is the code:
CDC bufferDC;
CBitmap bufferBitmap;
bufferDC.CreateCompatibleDC(&dc);
bufferBitmap.CreateCompatibleBitmap(&bufferDC, 300, 300);
bufferDC.SelectObject(bufferBitmap);
Graphics g(bufferDC);
g.Clear(Color::Green);
dc.BitBlt(0, 0, 300, 300, &bufferDC, 0, 0, SRCCOPY);
Instead of a green patch, I see a rectangle of dithered black and white dots. I even tried to save the bitmap to disk after the g.Clear() call. It is indeed a 1-bit depth file.
Any ideas what went wrong? Thanks.
A common mistake. A memory DC takes on the properties of the bitmap selected into it, no matter what compatibility it was created with. The default bitmap selected into a DC is monochrome. If you create a bitmap compatible with that DC, it will be monochrome too.
Create the bitmap to be compatible with the original DC, not the memory DC.
Both the bitnmap and the bufferDC should be compatible with dc (whatever device it refers to), not the bitmap compatible ... with its own DC.
Try to give &dc to CreateCopmpatibleBitmap.
Your code snippet does not show where the dc variable comes from. ThIs guy probably contains a monochrome bitmap, the default. You dont need it anyway. Instead, pass NULL to CreateCompatibleDC and it will be the same format as your display, which is probably color.