Keskustelu: Ohjelmointikysymykset: C++: Bittikartan kirjoittaminen

void WriteInt(fstream &file, int _int)
{
	char temp[4];
	temp[3] = _int >> 24;
	temp[2] = _int >> 16;
	temp[1] = _int >> 8;
	temp[0] = _int << 24 >> 24;

	file.write(temp, 4);
}

void WriteShort(fstream &file, short _short)
{
	char temp[2];
	temp[1] = _short >> 8;
	temp[0] = _short;

	file.write(temp, 2);
}

void CreateBitmap(std::string filename, int width, int height, short bits_per_channel, unsigned char* pixeldata)
{
	fstream myfile;
	myfile.open (filename, std::ios::binary | std::ios::out);

	short bits = bits_per_channel * 3;

	int header_size = 14;
	int dib_size = 40;

	int filesize = header_size+dib_size+width*height*3;

	// bitmap file header
	myfile << 'B' << 'M'; // bmp header
	WriteInt(myfile, filesize); // file size in bytes
	WriteInt(myfile, 0); // 2x 2-byte reserved
	WriteInt(myfile, header_size+dib_size); // pixel data offset

	// DIB header
	WriteInt(myfile, dib_size); // size of header in bytes
	WriteInt(myfile, width); // width in pixels
	WriteInt(myfile, height); // height in pixels
	WriteShort(myfile, 1); // has to be 1
	WriteShort(myfile, bits); // bits per pixel
	WriteInt(myfile, 0); // compression method (0 = none)
	WriteInt(myfile, width*height*3); // size of raw bitmap data
	WriteInt(myfile, 100); // horizontal resolution (pixel per meter)
	WriteInt(myfile, 100); // vertical resolution (pixel per meter)
	WriteInt(myfile, 0); // number of colors in palette
	WriteInt(myfile, 0); // number of important colors used

	// pixel data
	for(int i=0;i<width*height*3;i+=3)
	{
		myfile << pixeldata[i+2]; // b
		myfile << pixeldata[i+1]; // g
		myfile << pixeldata[i]; // r
	}

	myfile.close();
}

int main()
{
	srand(time(NULL)); // random seed

	int w = 100;
	int h = 100;

	unsigned char* yeah = new unsigned char[w*h*3];
	for(int i=0;i<w*h*3;i+=3)
	{
		yeah[i] = 255; // r
		yeah[i+1] = 255; // g
		yeah[i+2] = 255; // b
	}

	remove("media/yeah_buddy.bmp");
	CreateBitmap("media/yeah_buddy.bmp", w, h, 8, yeah);

	for(int i=0;i<w*h*3;i+=3)
	{
		yeah[i] = rand() % 255;
		yeah[i+1] = rand() % 255;
		yeah[i+2] = rand() % 255;
	}

	remove("media/yeah_buddy_2.bmp");
	CreateBitmap("media/yeah_buddy_2.bmp", w, h, 8, yeah);

	delete[] yeah;
}