Im wondering is it possible to get/set pixels of a 24 bit bitmap in the memory without using gdi/directx, I know how to get/set pixels in a bitmap file, but how would do that to the bits in the memory or dc?
Posted on 2001-02-27 05:50:00 by moxy
You should look up CreateCompatibleDC, CreateDIBSection and SelectObject. I can post some (ugly!) C source code if you'd like me to, which works. Or should work. Well, it's used in a commercial project, so it had better work ;-).
Posted on 2001-02-27 06:31:00 by f0dder
I can create the dc's and get the bitmap in there, but how would i view/edit the colorbits after selecting the bitmap into the memorydc? (edit the hbmp or hdc directly without gdi?) if you have the C source please post it =)
Posted on 2001-02-27 06:58:00 by moxy
okay, you asked for it :) It is for 32bpp (though by changing "a few things", you should be able to make it work for any resolution). After you have created the drawbuf, you can access drawbuf->buf directly. When done with your changes, blit the bitmap to screen the usual way.

typedef struct _DrawBuf {
	int		w;
	int		h;
	unsigned int*	buf;
	HBITMAP		hbmp;
	HDC		hdcbmp;
} DrawBuf;

static bool createDrawBuf(DrawBuf *db, int width, int height)
	memset(db, 0, sizeof(*db));
	db->w = width;
	db->h = height;

	db->bmp.bmiHeader.biBitCount = 32;

	// no colorTable since we're doing 32bpp.
	db->bmp.bmiHeader.biClrImportant = 0;
	db->bmp.bmiHeader.biClrUsed = 0;

	db->bmp.bmiHeader.biCompression = BI_RGB;

	// biHeight must be negative so we get a top-down bitmap. Fucked up MS.
	db->bmp.bmiHeader.biHeight = 0 - (db->h);

	db->bmp.bmiHeader.biPlanes = 1;
	db->bmp.bmiHeader.biSize = sizeof(db->bmp.bmiHeader);
	db->bmp.bmiHeader.biSizeImage = db->w * db->h * 4;
	db->bmp.bmiHeader.biWidth = db->w;

	db->hdcbmp = CreateCompatibleDC(NULL);
	if(db->hdcbmp == NULL) return false;

	db->hbmp = CreateDIBSection(db->hdcbmp, &db->bmp, DIB_RGB_COLORS, (void **) &db->buf, NULL, 0);
	if(db->hbmp == NULL) return false;

	SelectObject(db->hdcbmp, db->hbmp);

	return true;

static void killDrawBuf(DrawBuf *db)
	memset(db, 0, sizeof(*db));
Posted on 2001-02-27 07:06:00 by f0dder
After you select the bitmap into the dc, is it possible to edit it from there (setpixel,getpixel) directly? :( For example if i was to edit a bitmaps data section i would select the data into edi and write at a offset the new color. How would i edit a bitmap selected into a memoryDC without using set/get pixel? :ashamed:
Posted on 2001-02-27 08:49:00 by moxy
The way I do it is to draw in "gfxboard.buf", which is pretty easy. And then use a bitblt to display on screen. This means that you'll have to bitblt every time you have made changes (not per pixel please, but after all changes are done). This approach requires you to handle all (re)drawing of the area where you want to show the image. If you'd rather have a "normal" bitmap where windows handles the updating (good for a bitmap you don't change very often), you should probably use another technique. I hate working with bitmaps under windows :)
Posted on 2001-02-28 05:01:00 by f0dder
Thanks alot the code works great!! :)
Posted on 2001-02-28 06:25:00 by moxy