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;
- }
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