»imagebmp(): gute Funktion gefunden!

function imagebmp($im, $filename='', $bit=24, $compression=0) {
	// version 1.00
	if (!in_array($bit, array(1, 4, 8, 16, 24, 32))) {
		$bit = 24;
	}
	else if ($bit == 32) {
		$bit = 24;
	}
	$bits = pow(2, $bit);
	imagetruecolortopalette($im, true, $bits);
	$width = imagesx($im);
	$height = imagesy($im);
	$colors_num = imagecolorstotal($im);
	$rgb_quad = ''; 
	if ($bit <= 8) {
		for ($i = 0; $i < $colors_num; $i++) {
			$colors = imagecolorsforindex($im, $i);
			$rgb_quad .= chr($colors['blue']) . chr($colors['green']) . chr($colors['red']) . "\0";
		}
		$bmp_data = '';
		if ($compression == 0 || $bit < 8) {
			$compression = 0;
			$extra = ''; 
			$padding = 4 - ceil($width / (8 / $bit)) % 4;
			if ($padding % 4 != 0) {
				$extra = str_repeat("\0", $padding); 
			}
			for ($j = $height - 1; $j >= 0; $j --) {
				$i = 0;
				while ($i < $width) {
					$bin = 0;
					$limit = $width - $i < 8 / $bit ? (8 / $bit - $width + $i) * $bit : 0;
					for ($k = 8 - $bit; $k >= $limit; $k -= $bit) {
						$index = imagecolorat($im, $i, $j);
						$bin |= $index << $k;
						$i++;
					}
					$bmp_data .= chr($bin);
				}
				$bmp_data .= $extra;
			}
		}
		// RLE8
		else if ($compression == 1 && $bit == 8) {
			for ($j = $height - 1; $j >= 0; $j--) {
				$last_index = "\0";
				$same_num = 0;
				for ($i = 0; $i <= $width; $i++) {
					$index = imagecolorat($im, $i, $j);
					if ($index !== $last_index || $same_num > 255) {
						if ($same_num != 0) {
							$bmp_data .= chr($same_num) . chr($last_index);
						}
						$last_index = $index;
						$same_num = 1;
					}
					else {
						$same_num++;
					}
				}
				$bmp_data .= "\0\0";
			}
			$bmp_data .= "\0\1";
		}
		$size_quad = strlen($rgb_quad);
		$size_data = strlen($bmp_data);
	}
	else {
		$extra = '';
		$padding = 4 - ($width * ($bit / 8)) % 4;
		if ($padding % 4 != 0) {
			$extra = str_repeat("\0", $padding);
		}
		$bmp_data = '';
		for ($j = $height - 1; $j >= 0; $j--) {
			for ($i = 0; $i < $width; $i++) {
				$index  = imagecolorat($im, $i, $j);
				$colors = imagecolorsforindex($im, $index);
				if ($bit == 16) {
					$bin = 0 << $bit;
					$bin |= ($colors['red'] >> 3) << 10;
					$bin |= ($colors['green'] >> 3) << 5;
					$bin |= $colors['blue'] >> 3;
					$bmp_data .= pack("v", $bin);
				}
				else {
					$bmp_data .= pack("c*", $colors['blue'], $colors['green'], $colors['red']);
				}
			}
			$bmp_data .= $extra;
		}
		$size_quad = 0;
		$size_data = strlen($bmp_data);
		$colors_num = 0;
	}
	$file_header = 'BM' . pack('V3', 54 + $size_quad + $size_data, 0, 54 + $size_quad);
	$info_header = pack('V3v2V*', 0x28, $width, $height, 1, $bit, $compression, $size_data, 0, 0, $colors_num, 0);
	if ($filename != '') {
		$fp = fopen($filename, 'wb');
		fwrite($fp, $file_header . $info_header . $rgb_quad . $bmp_data);
		fclose($fp);
		return true;
	}
	echo $file_header . $info_header. $rgb_quad . $bmp_data;
	return true;
}