Combining Images with Regions

1.	Define the following global variables:

HWND hWndClient; /* Handle of the current child window */
RGNXFORM XForm; /* Structure for transforming display coordinates */
RECT rClientArea; /* Client area of the current window */
RECT rRgnRect; /* Rectangle that defines the region */
BITMAPHANDLE BitmapDst; /* Destination bitmap */
BITMAPHANDLE BitmapSrc; /* Source bitmap */
L_INT XDst; /* Column offset of the destination */
L_INT YDst; /* Row offset of the destination */
L_INT XSize;/* Pixel width of the rectangle to combine */
L_INT YSize;/* Pixel height of the rectangle to combine */
L_INT XSrc; /* Column offset of the source */
L_INT YSrc; /* Column offset of the source */

2.	Load two images as follows:

L_LoadBitmap(TEXT("c:\\sample1.cmp"), &BitmapDst, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL);
L_LoadBitmap (TEXT("C:\\sample2.cmp"), &BitmapSrc, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL);

3.	Get the client area of the current child window as follows:

GetClientRect(hWndClient, &rClientArea);

4.	Set RGNXFORM fields, assuming that the display rectangle is the same as the client area of the current child window as follows:

XForm.uViewPerspective = TOP_LEFT;
XForm.nXScalarNum = BITMAPWIDTH(&BitmapDst);
XForm.nXScalarDen = rClientArea.right;
XForm.nYScalarNum = BITMAPHEIGHT(&BitmapDst);
XForm.nYScalarDen = rClientArea.bottom;
XForm.nXOffset = 0;
XForm.nYOffset = 0;

5.	Specify a rectangle to define the region and then create a rectangular region as follows:

SetRect(&rRgnRect, rClientArea.right/8, rClientArea.bottom/8, rClientArea.right/2, rClientArea.bottom/2);
L_SetBitmapRgnRect(&BitmapDst, &XForm, &rRgnRect, L_RGN_SET);

6.	Specify a position in the top left part of the displayed image and use the full size of the source bitmap as follows:

XDst = BITMAPWIDTH(&BitmapDst) / 8;
YDst = BITMAPHEIGHT(&BitmapDst) / 8;
YSize = BITMAPHEIGHT(&BitmapSrc);
XSize = BITMAPWIDTH(&BitmapSrc);
XSrc = 0;
YSrc = 0;

7.	Combine BitmapDst with &BitmapSrc, using flags for an ordinary paste:

L_CombineBitmap(&BitmapDst, XDst, YDst, XSize, YSize, &BitmapSrc, XSrc, YSrc, CB_OP_ADD | CB_DST_0);

8.	At the end you should free the rectangle:

L_FreeBitmapRgn(&BitmapDst);