Advanced MFC Programming

Chapter 10. Bitmap
color bitmap, but we use only monochrom colors) is created by calling function CBitmap::
CreateCompatibleBitmap(…). Since the DC supports color bitmap (If the program is being run on a system
with a color monitor) , this will create a color bitmap compatible with the window DC.
Then we select the color bitmap and the binary bitmaps into the memory DCs and create the outline
mask images:
……
……
pBmpShadowOld=dcMono.SelectObject(&bmpShadow);
dcMono.FillSolidRect(0, 0, bm.bmWidth, bm.bmHeight, RGB(255, 255, 255));
dcMono.BitBlt
(
0, 0,
bm.bmWidth-1, bm.bmHeight-1,
&dcColor,
1, 1,
SRCCOPY
) ;
dcMono.BitBlt
(
0, 0,
bm.bmWidth, bm.bmHeight,
&dcColor,
0, 0,
MERGEPAINT
);
dcMono.SelectObject(pBmpShadowOld);
First we fill the mask bitmap with white color. Then we copy the patterns from the original image to
the mask bitmap image. When doing this copy, the first horizontal line (the upper-most line) and the first
vertical line (the left-most vertical line) are eleminated from the original image (Pixels with coordinates (0,
y) and (x, 0) are elemented, where x can be 0, 1, … , up to width of image -1; y can be 0, 1, …, up to height
of image -1). The colors contained in the souce bitmap will be automatically converted to black and white
colors when we call function CDC::BitBlt(…) because the target image is a binary bitmap. The souce
image is copied to the mask bitmap at the position of (0, 0). Then the original bitmap is inverted, and
merged with the mask image with bit-wise OR operation. Here flag MERGEPAINT allows the pixels in the
souce image and pixels in the target image to be combined in this way. After these operations, the binary
bitmap image will contain the outline that should be drawn with the shadowed color.
The following portion of the function generates the highlighted outline:
……
pBmpHilightOld=dcMono.SelectObject(&bmpHilight);
dcMono.BitBlt
(
0, 0,
bm.bmWidth, bm.bmHeight,
&dcColor,
0, 0,
SRCCOPY
);
dcMono.BitBlt
(
0, 0,
bm.bmWidth-1, bm.bmHeight-1,
&dcColor,
1, 1,
MERGEPAINT
);
dcMono.SelectObject(pBmpHilightOld);
dcColor.SelectObject(pBmpOld);
……
pBmpOld=dcColor.SelectObject(&bmpGray);
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