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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