Writes a BMP format file.

gistfile1.cpp

void Tracer::writeScreenToBmp()
{
    // short == 2 bytes
    // int   == 4 bytes

    struct BitMapFileHeader
    {
        short  magic;		
        int		size;
        short	reserved1;
        short	reserved2;
        int		offbits;
    };

    struct BitMapInfoHeader
    {
        int		size;
        int		width;
        int		height;
        short	planes;
        short	bitCount;
        int		compression;
        int		sizeImage;
        int		xPixelsPerMeter;
        int		yPixelsPerMeter;
        int		clrUsed;
        int		clrImportant;
    };

    struct BitMapFileHeader	header;
    struct BitMapInfoHeader	info;

    // magic bytes
    int extraBytes = (4 - (renderWidth * 3) % 4) % 4; // each row must be multiple of four
    int imageBufferSize = (renderWidth * 3 + extraBytes) * renderHeight;

    header.magic = 0x4d42;
    header.size	= 14 + 40 + imageBufferSize;
    header.reserved1 = 0;
    header.reserved2 = 0;
    header.offbits = 14 + 40;

    info.size = 40;
    info.width = renderWidth;
    info.height = renderHeight;
    info.planes = 1;
    info.bitCount = 24;
    info.compression = 0;
    info.sizeImage = imageBufferSize;
    info.xPixelsPerMeter = 2952;
    info.yPixelsPerMeter = 2952;
    info.clrUsed = 0;
    info.clrImportant = 0;

    char *imageBuffer = new char[imageBufferSize];

    // zero everything
    for (int i = 0; i < imageBufferSize; ++i)
        imageBuffer[i] = 0x00;

    for (int i = 0; i < screenSize; ++i ) {
        int x = i % renderWidth;
        int y = (i - x) / renderWidth;

        // use x and y to find offset n
        int n = (renderHeight - 1 - y) * (renderWidth * 3 + extraBytes) + (x * 3);

        imageBuffer[n]		= (char)screen[i].blue;
        imageBuffer[n+1]	= (char)screen[i].green;
        imageBuffer[n+2]	= (char)screen[i].red;
    }

    // write to file
    ofstream outputFile("image.bmp", ios::binary);

    // file header
    outputFile.write((char*)&header.magic, sizeof(header.magic));
    outputFile.write((char*)&header.size, sizeof(header.size));
    outputFile.write((char*)&header.reserved1, sizeof(header.reserved1));
    outputFile.write((char*)&header.reserved2, sizeof(header.reserved2));
    outputFile.write((char*)&header.offbits, sizeof(header.offbits));

    // info header and imageBuffer
    outputFile.write((char*)&info, sizeof(info));
    outputFile.write(imageBuffer, imageBufferSize);
    outputFile.close();

    // clean up
    delete [] imageBuffer;
}