getpixel() from a directdraw7 surface?
Author
I want a function that takes an x,y coordinate and a dd7 surface and returns to me a color value at that location. I've looked all over online and haven't found anything.
You need to look into "locking" and "direct memory access" (DMA) for surfaces.
Sadly, it's nowhere near as trivial as the GetPixel() from the GDI/Win32 camp, and it's prone to a large number of hurdles.
You need to specify
- Language of choice; presumably VB6 or C++
- Whether you have any solid format assumptions, or you want a general purpose solution
- Do you need a single pixel, or do you want all pixels?
hth
Jack
Sadly, it's nowhere near as trivial as the GetPixel() from the GDI/Win32 camp, and it's prone to a large number of hurdles.
You need to specify
- Language of choice; presumably VB6 or C++
- Whether you have any solid format assumptions, or you want a general purpose solution
- Do you need a single pixel, or do you want all pixels?
hth
Jack
Author
-C++
-I use SetDisplayMode to set a 32bit display but am using 24bit bitmaps, I don't know what format
-Just a single pixel at a time.
Thanks for any help
-I use SetDisplayMode to set a 32bit display but am using 24bit bitmaps, I don't know what format
-Just a single pixel at a time.
Thanks for any help
Author
This is my load bitmap function maybe it will help you determine what color format I would get back from a getpixel call? I'm using it to load 24bpp bitmaps made in mspaint.
int LoadBitmapResource(LPDIRECTDRAWSURFACE7 lpdds, int xDest, int yDest, char* fname)
{
HDC hSrcDC;
HDC hDestDC;
HBITMAP hbitmap;
BITMAP bmp;
hbitmap = (HBITMAP)LoadImage(ghinstance, fname, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
hSrcDC = CreateCompatibleDC(NULL);
SelectObject(hSrcDC, hbitmap);
GetObject(hbitmap, sizeof(BITMAP), &bmp);
lpdds->GetDC(&hDestDC);
BitBlt(hDestDC, xDest, yDest, bmp.bmWidth, bmp.bmHeight, hSrcDC, 0, 0, SRCCOPY);
lpdds->ReleaseDC(hDestDC);
DeleteDC(hSrcDC);
return(TRUE);
}
int LoadBitmapResource(LPDIRECTDRAWSURFACE7 lpdds, int xDest, int yDest, char* fname)
{
HDC hSrcDC;
HDC hDestDC;
HBITMAP hbitmap;
BITMAP bmp;
hbitmap = (HBITMAP)LoadImage(ghinstance, fname, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
hSrcDC = CreateCompatibleDC(NULL);
SelectObject(hSrcDC, hbitmap);
GetObject(hbitmap, sizeof(BITMAP), &bmp);
lpdds->GetDC(&hDestDC);
BitBlt(hDestDC, xDest, yDest, bmp.bmWidth, bmp.bmHeight, hSrcDC, 0, 0, SRCCOPY);
lpdds->ReleaseDC(hDestDC);
DeleteDC(hSrcDC);
return(TRUE);
}
If you want to use GetPixel() then you have to:
COLORREF GetBackBufferPixel(int x, int y)
{
HDC hDC;
//Get the backbuffer DC
//This changes everyframe, because the DC is changed.
BackBuffer->GetDC(&hDC);
COLORREF rgb = GetPixel(hDC,x,y);
//Release the DC, if you do not, you will get an error on next update
BackBuffer->ReleaseDC(hDC);
return rgb;
}
Now you'll want to use GetRValue(rgb), GetGValue(rgb), GetBValue(rgb)
Sadly, GetPixel I believe is way slower than the locking method which is also VERY slow. There is no nice way to deal with the backbuffer directly.
[Edited by - Halsafar on June 1, 2005 8:30:05 PM]
COLORREF GetBackBufferPixel(int x, int y)
{
HDC hDC;
//Get the backbuffer DC
//This changes everyframe, because the DC is changed.
BackBuffer->GetDC(&hDC);
COLORREF rgb = GetPixel(hDC,x,y);
//Release the DC, if you do not, you will get an error on next update
BackBuffer->ReleaseDC(hDC);
return rgb;
}
Now you'll want to use GetRValue(rgb), GetGValue(rgb), GetBValue(rgb)
Sadly, GetPixel I believe is way slower than the locking method which is also VERY slow. There is no nice way to deal with the backbuffer directly.
[Edited by - Halsafar on June 1, 2005 8:30:05 PM]
Author
Thanks, Ill try that. Fortunately it doesn't have to be very fast for my immediate purpost.
No problem.
I made a little error when typing that up for you but I bet you quickly caught it. I didn't put x,y in the GetPixel call. Anyway good luck with your project.
I made a little error when typing that up for you but I bet you quickly caught it. I didn't put x,y in the GetPixel call. Anyway good luck with your project.
Author
I'm working on pacman. I did it years ago in DOS mode 13h but now (after learning Win32) I am working on teaching myself DirectDraw and DirectInput, and then later Direct3D.
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