Posted on 2008-05-26 18:06
cacar 阅读(521)
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DirectX
一、关于Blt
直接通过主表面指针调用，指明源区域，源表面，目标区域，目标表面，Blt就可以。源表面和目标表面可以是同一个，不过不经常这样做。而且如果目标区域超出了目标表面的矩形范围，则会出现问题，因此必须裁剪。
二、关于Clipper
要设置DirectDraw裁剪，需要如下步骤
（1）创建裁剪器对象；
（2）创建裁剪序列（就是一个结构体保存的一系列RECT）；
（3）用IDIRECTDRAWCLIPPER::SetClipList()将裁剪器序列发送给裁剪器；
（4）用IDIRECTDRAWSURFACE7::SetClipper()将裁剪器同窗口或表面相关联。
封装该过程如下：
LPDIRECTDRAWCLIPPER DDraw_Attach_Clipper(LPDIRECTDRAWSURFACE7 lpdds,
int num_rects,
LPRECT clip_list)
{
// this function creates a clipper from the sent clip list and attaches
// it to the sent surface
int index; // looping var
LPDIRECTDRAWCLIPPER lpddclipper; // pointer to the newly created dd clipper
LPRGNDATA region_data; // pointer to the region data that contains
// the header and clip list
// first create the direct draw clipper
if (FAILED(lpdd->CreateClipper(0,&lpddclipper,NULL)))
return(NULL);
// now create the clip list from the sent data
// first allocate memory for region data
region_data = (LPRGNDATA)malloc(sizeof(RGNDATAHEADER)+num_rects*sizeof(RECT));
// now copy the rects into region data
memcpy(region_data->Buffer, clip_list, sizeof(RECT)*num_rects);
// set up fields of header
region_data->rdh.dwSize = sizeof(RGNDATAHEADER);
region_data->rdh.iType = RDH_RECTANGLES;
region_data->rdh.nCount = num_rects;
region_data->rdh.nRgnSize = num_rects*sizeof(RECT);
region_data->rdh.rcBound.left = 64000;
region_data->rdh.rcBound.top = 64000;
region_data->rdh.rcBound.right = -64000;
region_data->rdh.rcBound.bottom = -64000;
// find bounds of all clipping regions
for (index=0; index<num_rects; index++)
{
// test if the next rectangle unioned with the current bound is larger
if (clip_list[index].left < region_data->rdh.rcBound.left)
region_data->rdh.rcBound.left = clip_list[index].left;
if (clip_list[index].right > region_data->rdh.rcBound.right)
region_data->rdh.rcBound.right = clip_list[index].right;
if (clip_list[index].top < region_data->rdh.rcBound.top)
region_data->rdh.rcBound.top = clip_list[index].top;
if (clip_list[index].bottom > region_data->rdh.rcBound.bottom)
region_data->rdh.rcBound.bottom = clip_list[index].bottom;
} // end for index
// now we have computed the bounding rectangle region and set up the data
// now let's set the clipping list
if (FAILED(lpddclipper->SetClipList(region_data, 0)))
{
// release memory and return error
free(region_data);
return(NULL);
} // end if
// now attach the clipper to the surface
if (FAILED(lpdds->SetClipper(lpddclipper)))
{
// release memory and return error
free(region_data);
return(NULL);
} // end if
// all is well, so release memory and send back the pointer to the new clipper
free(region_data);
return(lpddclipper);
} // end DDraw_Attach_Clipper
上述过程可以如此调用
RECT rect_list[3] = {{},{},{}};
// 调用
LPDIRECTDRAWCLIPPER lpddclipper = DDraw_Attach_Clipper(lpddsback,3,rect_list);