setpixel,getpixel效率太低的问题

来源：互联网发布：mac 重做系统编辑：程序博客网时间：2024/04/27 13:42

setpixel,getpixel效率很低，尤其是在循环里面去这么做，速度慢的无法忍受，

用bitblt做了优化，代码如下，

原函数如下：

void gdiRectangleAlpha(HDC hdc,const RECT *rect,COLORREF color, unsigned char alpha)

{

if (!rect || !hdc)

{

return;

}

int xMin = rect->left;

int yMin = rect->top;

int xMax = rect->right;

int yMax = rect->bottom;

int x,y;

int r = GetRValue(color);

int g = GetGValue(color);

int b = GetBValue(color);

COLORREF clSrc;

int rSrc;

int gSrc;

int bSrc;

for (y = yMin; y < yMax; y++)

{

for (x = xMin; x < xMax; x++)

{

clSrc = GetPixel(hdc,x,y);

rSrc = GetRValue(clSrc);

gSrc = GetGValue(clSrc);

bSrc = GetBValue(clSrc);

rSrc = (rSrc * alpha + r * (255 - alpha)) >>8;

gSrc = (gSrc * alpha + g * (255 - alpha)) >>8;

bSrc = (bSrc * alpha + b * (255 - alpha)) >>8;

SetPixel(hdc,x,y,RGB(rSrc,gSrc,bSrc));

}

优化后的实现

void gdiRectangleAlpha(HDC hdc,const RECT *rect,COLORREF color, unsigned char alpha)

{

BYTE * g_pBits;

HDC g_hMemDC;

HBITMAP g_hBmp, g_hOldBmp;

if (!rect || !hdc)

{

return;

}

int xMin = rect->left;

int yMin = rect->top;

int xMax = rect->right;

int yMax = rect->bottom;

int x,y;

byte r = GetRValue(color);

byte g = GetGValue(color);

byte b = GetBValue(color);

COLORREF clSrc;

unsigned char rSrc;

unsigned char gSrc;

unsigned char bSrc;

g_hMemDC = ::CreateCompatibleDC(hdc);

if (!g_hMemDC)

{

::DeleteDC(hdc);

}

int iWidth = rect->right - rect->left;

int iHeight = rect->bottom - rect->top;

BYTE bmibuf[sizeof(BITMAPINFO) + 256 * sizeof(RGBQUAD)];

memset(bmibuf, 0, sizeof(bmibuf));

BITMAPINFO* pbmi = (BITMAPINFO*)bmibuf;

// BITMAPINFO pbmi;

pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);

pbmi->bmiHeader.biWidth = iWidth;

pbmi->bmiHeader.biHeight = iHeight;

pbmi->bmiHeader.biPlanes = 1;

pbmi->bmiHeader.biBitCount = 24;

pbmi->bmiHeader.biCompression = BI_RGB;

g_hBmp = ::CreateDIBSection(g_hMemDC, pbmi, DIB_RGB_COLORS, (void **)&g_pBits, 0, 0);

if (!g_hBmp)

{

::DeleteDC(g_hMemDC);

}

g_hOldBmp = (HBITMAP)::SelectObject(g_hMemDC, g_hBmp);

BitBlt(g_hMemDC,0,0,iWidth,iHeight,hdc,0,0,SRCCOPY);

// offset = y * (width * 24 / 8) + x * (24 / 8)

for (y = 0; y < iHeight; y++)

{

for (x = 0; x < iWidth; x++)

{

rSrc = g_pBits[y * iWidth * 3 + x * 3 + 2];

gSrc = g_pBits[y * iWidth * 3 + x * 3 + 1];

bSrc = g_pBits[y * iWidth * 3 + x * 3];

rSrc = (rSrc * alpha + r * (255 - alpha)) >>8;

gSrc = (gSrc * alpha + g * (255 - alpha)) >>8;

bSrc = (bSrc * alpha + b * (255 - alpha)) >>8;

g_pBits[y * iWidth * 3 + x * 3 + 2] = rSrc;

g_pBits[y * iWidth * 3 + x * 3 + 1] = gSrc;

g_pBits[y * iWidth * 3 + x * 3] = bSrc;

}

BitBlt(hdc, 0, 0, iWidth, iHeight, g_hMemDC, 0, 0, SRCCOPY);

SelectObject(g_hMemDC, g_hOldBmp);

DeleteObject(g_hBmp);

DeleteDC(g_hMemDC);

ReleaseDC(NULL, hdc);

}