[OpenGL] 获取画布背景的位图数据

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用OpenGL绘制好画面后可以将画面数据保存成位图

本文给出一个获取位图数据的函数：

// get data of canvas rendered with OpenGL// note : need to call delete[] for *pDatabool CaptureOpenGL(int& nWidth, int& nHeight, int& nPitch, BYTE** pData){static GLenum s_Format = GL_BGRA_EXT;static int s_nBytePerPixel = 4; // 4Byte : because pixel format is GL_BGRA_EXTnWidth = nHeight = nPitch = 0;*pData = NULL;GLint aViewport[4];glGetIntegerv(GL_VIEWPORT, aViewport);int width = aViewport[2];int height = aViewport[3]; if ((width * height) <= 0)return false;int pitch = width * s_nBytePerPixel;int len = pitch * height; BYTE* pBuffer = new BYTE[len];if (!pBuffer)return false; glPixelStorei(GL_PACK_ALIGNMENT, 1);glPixelStorei(GL_PACK_ROW_LENGTH, 0);glPixelStorei(GL_PACK_SKIP_ROWS, 0);glPixelStorei(GL_PACK_SKIP_PIXELS, 0);GLenum lastBuffer;glGetIntegerv(GL_READ_BUFFER, (GLint*)&lastBuffer);glReadBuffer(GL_FRONT);glReadPixels(0, 0, width, height, s_Format, GL_UNSIGNED_BYTE, pBuffer);glReadBuffer(lastBuffer); // reset value of alpha channel with 255. because sometimes the value is 0, such as CS1.6 CWindowTool::ResetAlpha(pBuffer, len, 255); // this function should be completed by yourselfnWidth = width;nHeight = height;nPitch = pitch;*pData = pBuffer;return true;}

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