php使用GD库生成bmp格式的图片(imagebmp)

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Release： 2016-07-25 09:07:18

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/**
* 创建bmp格式图片
*
* @author: legend
* @description: create Bitmap-File with GD library
* @version: 0.1
*
* @param resource $im 图像资源
* @param string $filename 如果要另存为文件，请指定文件名，为空则直接在浏览器输出
* @param integer $bit 图像质量(1、4、8、16、24、32位)
* @param integer $compression 压缩方式，0为不压缩，1使用RLE8压缩算法进行压缩
*
* @return integer
*/
function imagebmp(&$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*”, 0×28, $width, $height, 1, $bit, $compression, $size_data, 0, 0, $colors_num, 0);
// 写入文件
if ($filename != ”)
{
$fp = fopen(“test.bmp”, “wb”);
fwrite($fp, $file_header);
fwrite($fp, $info_header);
fwrite($fp, $rgb_quad);
fwrite($fp, $bmp_data);
fclose($fp);
return 1;
}
// 浏览器输出
header(“Content-Type: image/bmp”);
echo $file_header . $info_header;
echo $rgb_quad;
echo $bmp_data;
return 1;
}
?>