PHP仿GD生成BMP图片

PHP仿GD生成BMP图片

function imagebmp(&$im, $filename = '', $bit = 8, $compression = 0)
{
	if (!in_array($bit, array(1, 4, 8, 16, 24, 32)))
	{
		$bit = 8;
	}
	else if ($bit == 32) // todo:32 bit
	{
		$bit = 24;
	}
	$bits = pow(2, $bit);

	// 调整调色板
	imagetruecolortopalette($im, true, $bits);
	$width  = imagesx($im);
	$height = imagesy($im);
	$colors_num = imagecolorstotal($im);

	if ($bit 	{
		// 颜色索引
		$rgb_quad = '';
		for ($i = 0; $i 		{
			$colors = imagecolorsforindex($im, $i);
			$rgb_quad .= chr($colors['blue']) . chr($colors['green']) . chr($colors['red']) . "\0";
		}

		// 位图数据
		$bmp_data = '';

		// 非压缩
		if ($compression == 0 || $bit 		{
			if (!in_array($bit, array(1, 4, 8)))
			{
			$bit = 8;
			}
			$compression = 0;

			// 每行字节数必须为4的倍数，补齐。
			$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 				{
					$bin = 0;
					$limit = $width - $i
					for ($k = 8 - $bit; $k >= $limit; $k -= $bit)
					{
						$index = imagecolorat($im, $i, $j);
						$bin |= $index 						$i ++;
					}

					$bmp_data .= chr($bin);
				}

				$bmp_data .= $extra;
			}
		}
		// RLE8 压缩
		else if ($compression == 1 && $bit == 8)
		{
			for ($j = $height - 1; $j >= 0; $j --)
			{
				$last_index = "\0";
				$same_num   = 0;
				for ($i = 0; $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
	{
	// 每行字节数必须为4的倍数，补齐。
		$extra = '';
		$padding = 4 - ($width * ($bit / 8)) % 4;
		if ($padding % 4 != 0)
		{
			$extra = str_repeat("\0", $padding);
		}
		// 位图数据
		$bmp_data = '';
		for ($j = $height - 1; $j >= 0; $j --)
		{
			for ($i = 0; $i 			{
				$index  = imagecolorat($im, $i, $j);
				$colors = imagecolorsforindex($im, $index);
				if ($bit == 16)
				{
					$bin = 0
					$bin |= ($colors['red'] >> 3) 					$bin |= ($colors['green'] >> 3) 					$bin |= $colors['blue'] >> 3;

					$bmp_data .= pack("v", $bin);
				}
				else
				{
					$bmp_data .= pack("c*", $colors['blue'], $colors['green'], $colors['red']);
				}

				// todo: 32bit;
			}
			$bmp_data .= $extra;
		}
		$size_quad = 0;
		$size_data = strlen($bmp_data);
		$colors_num = 0;
	}

	// 位图文件头
	$file_header = "BM" . pack("V3", 54 + $size_quad + $size_data, 0, 54 + $size_quad);

	// 位图信息头
	$info_header = pack("V3v2V*", 0x28, $width, $height, 1, $bit, $compression, $size_data, 0, 0, $colors_num, 0);

	// 写入文件
	if ($filename != '')
	{
		$fp = fopen($filename, "wb");
		fwrite($fp, $file_header);
		fwrite($fp, $info_header);
		fwrite($fp, $rgb_quad);
		fwrite($fp, $bmp_data);
		fclose($fp);
		return true;
	}

	// 浏览器输出
	header("Content-Type: image/bmp");
	echo $file_header . $info_header;
	echo $rgb_quad;
	echo $bmp_data;
	return true;
}