Region and masks - Dev Shed

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May 29th, 2003, 06:37 AM

Nille

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Region and masks

Hi,
Sorry for asking a lot of questions... It's a good way to learn, so I hope you can forgive me.

I would like to make region from a mask. But I really don't want to combine rectangles for every pixel. I don't think that's a good approach. What I would like to do, is to have a layout like this:

Code:

00000111111111100000
01111111111111111000
01111100011110001110
01111111111111111110
01111111110011111110
01111001111111001110
00111110000000111100
00001111111111100000

I would then like to respond to hit-tests by simply checking if the specified coordinate is 1 or 0. I would also return the bounds of the region and could also combine it with other regions, if that would be required. How can I accomplish this? It would be an "implementation" of HRGN, or something.

Thanks in advance,
Nille

May 29th, 2003, 09:10 PM

TechNoFear

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Try

PtInRect() or PtInRegion() with the params from the mouse click or use GetCursor()

ClientToScreen() and ScreenToClient() may be helpfull in converting the coods.

__________________
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Frank Zappa

May 30th, 2003, 10:02 AM

Nille

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I want to respond to these method calls myself. Think of it like this:

Code:

      |--- Rectangle
HRGN -|--- Ellipse
      |--- MyImageRegion

I create a mask from a bitmap and return a valid HRGN. I then want to perform hit tests.

Code:

HRGN hRgn = CreateCustomRegion("c:\\test.bmp");
if(PtInRegion(hRgn, 10, 10)) // <---- !!!
{
   //...
}

I have no idea how regions work. I can image they do something like this:

Code:

((SomeStruct*)hRgn)->IsPointInRegion(hRgn, x, y);

The thing is, I want to do the hit test on my own, but I want the HRGN to be treated as any other HRGN.

Imaging that HRGN was an abstract class, looking like this:

Code:

abstract class Region
{
   abstract bool PtInRegion(int x, int y);
}

You could then make your own implementation of the abstract class. This is what I want to do. I want to make my own implementation of HRGN. Is it possible?

June 4th, 2003, 01:34 PM

azntekkan

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Hi, I don't know if this is exactly what your looking for, but i found this code written by another programmer while i was trying to create window skins. It allows you to create a region using a bitmap and specifying the rgb value of the transparent colour.

PHP Code:


		
			
 HRGN BitmapToRegion (HBITMAP hBmp, COLORREF cTransparentColor)

{

    HRGN hRgn = NULL;



    if (hBmp)

    {

        // Create a memory DC inside which we will scan the bitmap content

        HDC hMemDC = CreateCompatibleDC(NULL);

        if (hMemDC)

        {

            // Get bitmap size

            BITMAP bm;

            GetObject(hBmp, sizeof(bm), &bm);



            // Create a 32 bits depth bitmap and select it into the memory DC 

            BITMAPINFOHEADER RGB32BITSBITMAPINFO = {    

                    sizeof(BITMAPINFOHEADER),    // biSize 

                    bm.bmWidth,                    // biWidth; 

                    bm.bmHeight,                // biHeight; 

                    1,                            // biPlanes; 

                    32,                            // biBitCount 

                    BI_RGB,                        // biCompression; 

                    0,                            // biSizeImage; 

                    0,                            // biXPelsPerMeter; 

                    0,                            // biYPelsPerMeter; 

                    0,                            // biClrUsed; 

                    0                            // biClrImportant; 

            };

            VOID * pbits32; 

            HBITMAP hbm32 = CreateDIBSection(hMemDC, (BITMAPINFO *)&RGB32BITSBITMAPINFO, DIB_RGB_COLORS, &pbits32, NULL, 0);

            if (hbm32)

            {

                HBITMAP holdBmp = (HBITMAP)SelectObject(hMemDC, hbm32);



                // Create a DC just to copy the bitmap into the memory DC

                HDC hDC = CreateCompatibleDC(hMemDC);

                if (hDC)

                {

                    // Get how many bytes per row we have for the bitmap bits (rounded up to 32 bits)

                    BITMAP bm32;

                    GetObject(hbm32, sizeof(bm32), &bm32);

                    while (bm32.bmWidthBytes % 4)

                        bm32.bmWidthBytes++;



                    // Copy the bitmap into the memory DC

                    HBITMAP holdBmp = (HBITMAP)SelectObject(hDC, hBmp);

                    BitBlt(hMemDC, 0, 0, bm.bmWidth, bm.bmHeight, hDC, 0, 0, SRCCOPY);



                    // For better performances, we will use the ExtCreateRegion() function to create the

                    // region. This function take a RGNDATA structure on entry. We will add rectangles by

                    // amount of ALLOC_UNIT number in this structure.

                    #define ALLOC_UNIT    100

                    DWORD maxRects = ALLOC_UNIT;

                    HANDLE hData = GlobalAlloc(GMEM_MOVEABLE, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects));

                    RGNDATA *pData = (RGNDATA *)GlobalLock(hData);

                    pData->rdh.dwSize = sizeof(RGNDATAHEADER);

                    pData->rdh.iType = RDH_RECTANGLES;

                    pData->rdh.nCount = pData->rdh.nRgnSize = 0;

                    SetRect(&pData->rdh.rcBound, MAXLONG, MAXLONG, 0, 0);



                    // Keep on hand highest and lowest values for the "transparent" pixels

                    BYTE lr = GetRValue(cTransparentColor);

                    BYTE lg = GetGValue(cTransparentColor);

                    BYTE lb = GetBValue(cTransparentColor);

                    



                    // Scan each bitmap row from bottom to top (the bitmap is inverted vertically)

                    BYTE *p32 = (BYTE *)bm32.bmBits + (bm32.bmHeight - 1) * bm32.bmWidthBytes;

                    for (int y = 0; y < bm.bmHeight; y++)

                    {

                        // Scan each bitmap pixel from left to right

                        for (int x = 0; x < bm.bmWidth; x++)

                        {

                            // Search for a continuous range of "non transparent pixels"

                            int x0 = x;

                            LONG *p = (LONG *)p32 + x;

                            while (x < bm.bmWidth)

                            {

                                BYTE b = GetRValue(*p);

                                if (b == lr)

                                {

                                    b = GetGValue(*p);

                                    if (b == lg )

                                    {

                                        b = GetBValue(*p);

                                        if (b ==lb )

                                            // This pixel is "transparent"

                                            break;

                                    }

                                }

                                p++;

                                x++;

                            }



                            if (x > x0)

                            {

                                // Add the pixels (x0, y) to (x, y+1) as a new rectangle in the region

                                if (pData->rdh.nCount >= maxRects)

                                {

                                    GlobalUnlock(hData);

                                    maxRects += ALLOC_UNIT;

                                    hData = GlobalReAlloc(hData, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), GMEM_MOVEABLE);

                                    pData = (RGNDATA *)GlobalLock(hData);

                                }

                                RECT *pr = (RECT *)&pData->Buffer;

                                SetRect(&pr[pData->rdh.nCount], x0, y, x, y+1);

                                if (x0 < pData->rdh.rcBound.left)

                                    pData->rdh.rcBound.left = x0;

                                if (y < pData->rdh.rcBound.top)

                                    pData->rdh.rcBound.top = y;

                                if (x > pData->rdh.rcBound.right)

                                    pData->rdh.rcBound.right = x;

                                if (y+1 > pData->rdh.rcBound.bottom)

                                    pData->rdh.rcBound.bottom = y+1;

                                pData->rdh.nCount++;



                                // On Windows98, ExtCreateRegion() may fail if the number of rectangles is too

                                // large (ie: > 4000). Therefore, we have to create the region by multiple steps.

                                if (pData->rdh.nCount == 2000)

                                {

                                    HRGN h = ExtCreateRegion(NULL, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), pData);

                                    if (hRgn)

                                    {

                                        CombineRgn(hRgn, hRgn, h, RGN_OR);

                                        DeleteObject(h);

                                    }

                                    else

                                        hRgn = h;

                                    pData->rdh.nCount = 0;

                                    SetRect(&pData->rdh.rcBound, MAXLONG, MAXLONG, 0, 0);

                                }

                            }

                        }



                        // Go to next row (remember, the bitmap is inverted vertically)

                        p32 -= bm32.bmWidthBytes;

                    }



                    // Create or extend the region with the remaining rectangles

                    HRGN h = ExtCreateRegion(NULL, sizeof(RGNDATAHEADER) + (sizeof(RECT) * maxRects), pData);

                    if (hRgn)

                    {

                        CombineRgn(hRgn, hRgn, h, RGN_OR);

                        DeleteObject(h);

                    }

                    else

                        hRgn = h;



                    // Clean up

                    SelectObject(hDC, holdBmp);

                    DeleteDC(hDC);

                }



                DeleteObject(SelectObject(hMemDC, holdBmp));

            }



            DeleteDC(hMemDC);

        }    

    }



    return hRgn;

}

Only thing is I have no idea how this code works, maybe if someone could figure it out and explain it. I've tried askin the guy who wrote it, but it turns out it was posted like 3 years ago so he isn't replying.

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