vaps 源码修改记录4

为了测试从opengl层读取像素是否正确，写了一个函数把读取的像素写入到bmp图片中。

读取opengl绘制到窗口中的像素，在vxtPLWindowImpl.cpp的vEndDraw函数中，

在SwapBuffers后面，添加读取像素数据并写入bmp图片的函数。

#pragma pack(push)
#pragma pack(1)

typedef struct
{
    WORD bfType;
    DWORD bfSize;
    WORD bfReserved1;
    WORD bfReserved2;
    DWORD bfOffBits;
}BIT_MAP_FILE_HEADER;

typedef struct
{
    DWORD biSize;
    DWORD biWidth;
    DWORD biHeight;
    WORD biPlanes;
    WORD biBitCount;
    DWORD biCompression;
    DWORD biSizeImage;
    DWORD biXPelsPerMeter;
    DWORD biYPelsPerMeter;
    DWORD biClrUsed;
    DWORD biClrImportant;
}BIT_MAP_INFO_HEADER;

void grabBmp(bool alpha)
{
    int ByteCount = alpha ? 4 : 3;
    int PixelLength = 0;

    if(alpha)
    {
        PixelLength = WindowWidth * WindowHeight * ByteCount;
    }
    else
    {
        int AlignmentWidth = WindowWidth * ByteCount;
        while( AlignmentWidth % 4 != 0 )
            ++AlignmentWidth;
        PixelLength = AlignmentWidth * WindowHeight;
    }

    GLubyte* pPixelData = (GLubyte*)malloc(PixelLength);  
    if( pPixelData == 0 )
        exit(0);

    FILE* pWritingFile = fopen("D:\\grab.bmp", "wb+");
    if( pWritingFile == 0 )
        exit(0);

    BIT_MAP_FILE_HEADER bmp_map_file;
    memset(&bmp_map_file, 0, sizeof(BIT_MAP_FILE_HEADER));
    bmp_map_file.bfType = 0x4d42;
    bmp_map_file.bfSize = sizeof(BIT_MAP_FILE_HEADER) + sizeof(BIT_MAP_INFO_HEADER) + PixelLength;
    bmp_map_file.bfOffBits = sizeof(BIT_MAP_FILE_HEADER) + sizeof(BITMAPINFOHEADER);
    fwrite(&bmp_map_file, sizeof(BIT_MAP_FILE_HEADER), 1, pWritingFile);

    BIT_MAP_INFO_HEADER bmp_map_info;
    memset(&bmp_map_info, 0, sizeof(BITMAPINFOHEADER));
    bmp_map_info.biSize = sizeof(BITMAPINFOHEADER);
    bmp_map_info.biHeight = WindowHeight;
    bmp_map_info.biWidth = WindowWidth;
    bmp_map_info.biSizeImage = PixelLength;
    bmp_map_info.biCompression = BI_RGB;
    bmp_map_info.biBitCount = ByteCount * 8;
    bmp_map_info.biPlanes = 1;
    fwrite(&bmp_map_info, sizeof(BIT_MAP_INFO_HEADER), 1, pWritingFile);
	
    glReadBuffer(GL_FRONT);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
    if(alpha)
	glReadPixels(0, 0, WindowWidth, WindowHeight, GL_RGBA, GL_UNSIGNED_BYTE, pPixelData);
    else
	glReadPixels(0, 0, WindowWidth, WindowHeight, GL_BGR_EXT, GL_UNSIGNED_BYTE, pPixelData);
    fwrite(pPixelData, PixelLength, 1, pWritingFile);

    fclose(pWritingFile);
    free(pPixelData);
}