A strange problem with regions

Hi!

I'm trying to loop through pixels of a bitmap, check for their RGB values and add to a region if they match with a specified color.

Code:

---

        for(WORD y=0; y<wBmpHeight; y++)
        {
                for(WORD x=0; x<wBmpWidth; x++)
                {
                        for(std::map<char*, CMould>::iterator it=moulds.begin(); it!=moulds.end(); it++) //this map holds 26 different color values and region handles
                        {
                                if(RGB(pPixels[p+2], pPixels[p+1], pPixels[p]) == it->second.trnsphRGB)
                                { //if the colors match
                                        int iRes = CombineRgn(it->second.regionHandle,
                                                            it->second.regionHandle,
                                                            CreateRectRgn(x, y, x+1, y+1), RGN_XOR); //add this pixel to the region
                                }
                        }
                        p+=3;
                }
                itoa(y, pOut, 10); //just to display the current y line
                SetWindowText(hwnd, pOut);
        }

---

All goes well and CombineRgn returns COMPLEXREGION (success) until line 138, pixel 514. The function returns ERROR on this and further pixels. I found out with GetLastError() that the error code is 6 (invalid handle). I don't get why it->second.regionHandle is invalid, because the debugger shows the exact same handle address for both- successful and unsuccessful calls to CombineRgn.

The CMould class is nothing special, regionHandle is initialized in the constructor.

Header:

Code:

---

#ifndef MOULD_H
#define MOULD_H

class CMould
{
public:
        CMould(COLORREF color, char** shouts);
        CMould(){}
        HRGN regionHandle;
        COLORREF trnsphRGB;
        char** pShouts;
};

#endif

---

CPP:

Code:

---

#include "stdafx.h"

CMould::CMould(COLORREF color, char** shouts)
{
        trnsphRGB=color;
        memcpy(pShouts, shouts, sizeof shouts);
        regionHandle = CreateRectRgn(0, 0, 1, 1);
}

---

I can't think of what might be causing it.
Thanks for any help.

I suspect you are just creating a region too complicated for Windows to deal with.

Regions are a screwy thing in the API, my friend. They are actually a very resource consuming object. Thus memory leaking is always lurking around the corner.

Rasterization is a good way around this (in my experience). Instead of adding each pixel to your region at once, add code that does something like:

Example:

Code:

---

// Sorry for not being up on my MFC... but you should be able to MFC-ify this.
RECT line = {0,0,0,0};
bool inside = false

for(int y = 0; y < wBmpHeight; ++y)
{
    line.top = y;
    line.bottom = y+1;

    for(int x = 0; x < wBmpWidth; ++x)
    {
        // I am switching more to pseudo-coding now, but you get the idea :)
        if(RGB(pixel(y*wBmpWidth+x)) == myTransparentColor)
        {
            if(!inside)
              line.left = x;
        } else
        {
            if(inside)
            {
              line.right = x-1;  // This makes it go back to the last pixel which was good.
              inside = false;

              HRGN extra = CreateRectRgnIndirect(&line);
              CombineRgn(second, second, extra, RGN_XOR);
              DeleteObject(extra); // this is actually probably what killed your code, btw.
            }
        }
    }
 
    // Make sure to finish a line too
    if(inside)
    {
        line.right = x-1;  // This makes it go back to the last pixel which was good.
        inside = false;

        HRGN extra = CreateRectRgnIndirect(&line);
        CombineRgn(second, second, extra, RGN_XOR);
        DeleteObject(extra); // again, we don't want memory leaks.
    }
}

---

Quote:

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Originally Posted by brewbuck

I suspect you are just creating a region too complicated for Windows to deal with.

---

hahaha! You are officially my favorite member.

Quote:

---

Originally Posted by master5001

Code:

---

              DeleteObject(extra); // this is actually probably what killed your code, btw.

---

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You are MY favorite member now :) Thanks, it works flawlessly now, hadn't thought about deleting GDI objects before posting.

Thanks again!

No problemo. I have run into issues like that before and they are so painfully difficult to debug.