The principle of transparent Bitmap in MFC

In short, is constantly repeatedly masking "filter out" Transparent color on the line, first to the entire code, followed by detailed introduction.

void Ctransdlg::onpaint () {CPAINTDC DC (this); CMEMDC m_dc;if (!M_DC) m_dc. LoadBitmap (IDB_BITMAP4); CMEMDC dcimage (100,100,&DC); CBitmap Bmpmask;bmpmask.createbitmap (100,100,1,1,null); CDC Dcmask;dcmask.createcompatibledc (&DC);d cmask.selectobject (bmpmask);d Cimage.bitblt (0,0,100,100,&m_dc , 0,0,srccopy);d c.         BitBlt (10,10,100,100,&m_dc,0,0,srccopy); Display Figure 1DC.      BitBlt (120,10,100,100,&dcmask,0,0,srccopy); Display Figure 2dcimage.setbkcolor (RGB (255,0,0));d Cmask.bitblt (0,0,100,100,&dcimage,0,0,srccopy);d C.      BitBlt (230,10,100,100,&dcmask,0,0,srccopy); Display Figure 3dc.      BitBlt (340,10,100,100,&dcimage,0,0,srccopy); Display Figure 4dcimage.setbkcolor (RGB (0,0,0));d Cimage.settextcolor (RGB (255,255,255));d C. BitBlt (450,10,100,100,&dcimage,0,0,srccopy);//Display Figure 5dcimage.bitblt (0,0,100,100,&dcmask,0,0,srcand);d C. BitBlt (10,120,100,100,&dcimage,0,0,srccopy);//Display Figure 6DC. BitBlt (120,120,100,100,&dcmask,0,0,srccopy);//Display Figure 7DC. SetBkColor (RGB (255,255,255));d C. BitBlt (230,120,100,100,&DCMASk,0,0,srcand);//Display Figure 8DC. BitBlt (230,120,100,100,&dcimage,0,0,srcpaint);//Display Figure 8}

M_dc. LoadBitmap (IDB_BITMAP4);     Loading the original, is the following, from the red, green, yellow composition, White is the background, not the original image

CMEMDC dcimage (100,100,&DC);//The demonstration principle of a total of three dc,dc to understand as a canvas, Dcimage is a temporary DC, can also be understood as a temporary canvas of 100x100, the original image is not so large, So the background will be revealed;

CBitmap Bmpmask;

CBitmap Bmpmask;bmpmask.createbitmap (100,100,1,1,null);    Create a monochrome bitmap, which you want to see, must be drawn on the canvas, which is copied to the CDC Dcmask;dcmask.createcompatibledc (&DC) on the (BITBLT) DC;           Create a mask with the canvas dcmask.selectobject (bmpmask);             Dcimage.bitblt the monochrome picture on the canvas (0,0,100,100,&m_dc,0,0,srccopy);   M_DC the original copy on this canvas to the temporary canvas dcimage <pre name= "code" class= "CPP" >DC. BitBlt (10,10,100,100,&m_dc,0,0,srccopy);         Displays the original DC on the final canvas DC. BitBlt (120,10,100,100,&dcmask,0,0,srccopy);      Displays a monochrome mask bitmap on the final canvas DC

Dcimage.setbkcolor (RGB (255,0,0));              Set the red color to dcimage the background color of the canvas, which is transparent dcmask.bitblt (0,0,100,100,&dcimage,0,0,srccopy); Dcimage copy himself to Dcmask, tell him red is the background color, dcmask can only show two colors, so dcimage on the red Place White, the other place is the black DC. BitBlt (230,10,100,100,&dcmask,0,0,srccopy);      Show Dcmask this canvas dc.bitblt (340,10,100,100,&dcimage,0,0,srccopy);      Show Dcimage This canvas

Dcimage.setbkcolor (RGB (0,0,0));              Dcimage set Black to Background color Dcimage.settextcolor (RGB (255,255,255));d C. BitBlt (450,10,100,100,&dcimage,0,0,srccopy);//Display Dcimage

Dcimage.bitblt (0,0,100,100,&dcmask,0,0,srcand),//dcimage and Dcmask, note that the transparent color of dcimage is black at this time, So the black in the Dcmask to the dcimage on the Transparent Color dc.bitblt (10,120,100,100,&dcimage,0,0,srccopy);//Display Dcimagedc.bitblt ( 120,120,100,100,&dcmask,0,0,srccopy);//Show Dcmask the  first is the original Dcimage, the second is Dcmask, and the third is the later Dcimage

dc. SetBkColor (RGB (255,255,255)); <span style= "White-space:pre" ></span>//the transparent color of the final canvas DC is set to white DC. BitBlt (230,120,100,100,&dcmask,0,0,srcand);//dcmask with the final canvas and Dc.bitblt (230,120,100,100,&dcimage,0,0, Srcpaint);//dcimage with the final canvas or the   first one is Dcmask, the second is Dcimage, and the third is the final effect.

The principle of transparent Bitmap in MFC