<?php
/*************************************************************
# 076 License

Copyright (c) テクニカル諏訪子

Permission is hereby granted to any person obtaining a copy of the software
Little Beast (the "Software") to use, modify, merge, copy, publish, distribute,
sublicense, and/or sell copies of the Software, subject to the following conditions:

    1. **Origin Attribution**:
       - You must not misrepresent the origin of the Software; you must not claim
         you created the original Software.
       - If the Software is used in a product, you must either:
         a. Provide clear attribution in the product's documentation, user interface,
            or other visible areas, **OR**
         b. Pay the original developers a fee they specify in writing.
    2. **Usage Restriction**:
       - The Software, or any derivative works, dependencies, or libraries
         incorporating it, must not be used for censorship or to suppress freedom of
         speech, expression, or creativity. Prohibited uses include, but are not
         limited to:
         - Censorship of so-called "hate speech", visuals, non-mainstream opinions,
           ideas, or objective reality.
         - Tools or systems designed to restrict access to information or
           artistic works.
    3. **Notice Preservation**:
       - This license and the above copyright notice must remain intact in all copies
         of the source code.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
namespace Std\Lib\Image;

/**
 * BMP（Windows・OS/2）
 *
 * ヘッダー：OS/2 1.x（12バイト）、OS/2 2.x（16～64バイト）、BITMAPINFOHEADER（40）、V2（52）、V3（56）、V4（108）、V5（124）
 * 画素：1・2・4・8ビット（パレット）、16・24・32ビット（既定の並び又はビットフィールド）
 * 圧縮：無し、RLE8、RLE4、BITFIELDS、ALPHABITFIELDS、OS/2のRLE24、埋め込んだPNG・JPEG
 * 下から上（既定）と上から下（丈が負）
 */
class Bmp implements ImageInterface {
  private const RGB = 0, RLE8 = 1, RLE4 = 2, BITFIELDS = 3, JPEG = 4, PNG = 5, ALPHABITFIELDS = 6;

  public function parse(string $file): \stdClass {
    $h = $this->header((string)file_get_contents($file, false, null, 0, 1024));
    return (object)[
      'width' => $h['width'],
      'height' => $h['height'],
      'bitDepth' => $h['bits'],
      'headerSize' => $h['dib'],
      'compression' => $h['comp'],
      'topDown' => $h['topDown'],
      'colors' => $h['colors'],
      'hasAlpha' => $h['masks'][3] !== 0,
    ];
  }

  /**
   * ヘッダーを読む
   */
  private function header(string $d): array {
    if (strlen($d) < 26 || substr($d, 0, 2) !== 'BM') throw new \RuntimeException('BMPではありません。');
    $offset = unpack('V', substr($d, 10, 4))[1];
    $dib = unpack('V', substr($d, 14, 4))[1];
    if (strlen($d) < 14 + min($dib, 64)) throw new \RuntimeException('BMPのヘッダーが途中で切れています。');
    $os2 = false;
    if ($dib === 12) {
      // OS/2 1.x：大きさは16ビット、パレットは3バイト
      $h = unpack('vwidth/vheight/vplanes/vbits', substr($d, 18, 8));
      $h += ['comp' => self::RGB, 'colors' => 0];
      $os2 = true;
    } else if ($dib >= 16) {
      $h = unpack('lwidth/lheight/vplanes/vbits', substr($d, 18, 12));
      $more = $dib >= 40 ? unpack('Vcomp/Vsize/lxppm/lyppm/Vcolors', substr($d, 30, 20)) : ['comp' => 0, 'colors' => 0];
      $h += $more;
      // OS/2 2.xは圧縮の番号が違う（3 = ハフマン、4 = RLE24）
      $os2 = $dib === 16 || $dib === 64;
    } else {
      throw new \RuntimeException("未対応のBMPのヘッダーです（{$dib}バイト）。");
    }
    $topDown = $h['height'] < 0;
    $h['height'] = abs($h['height']);
    Bitmap::check($h['width'], $h['height']);
    if (!in_array($h['bits'], [1, 2, 4, 8, 16, 24, 32], true) && !in_array($h['comp'], [self::JPEG, self::PNG], true)) {
      throw new \RuntimeException("未対応のBMPのビット深さです（{$h['bits']}）。");
    }

    // ビットフィールド：V2以上はヘッダーの中、40バイトのヘッダーは後ろに続く
    $masks = [0, 0, 0, 0];
    $palAt = 14 + $dib;
    if ($h['comp'] === self::BITFIELDS && !$os2 || $h['comp'] === self::ALPHABITFIELDS) {
      $n = $h['comp'] === self::ALPHABITFIELDS ? 4 : 3;
      if ($dib >= 52) {
        $masks = array_values(unpack('V4', substr($d, 54, 16) ?: str_repeat("\0", 16)));
        if ($dib < 56) $masks[3] = 0;
      } else {
        $masks = array_values(unpack("V{$n}", substr($d, $palAt, $n * 4)));
        if ($n === 3) $masks[] = 0;
        $palAt += $n * 4;
      }
    } else if ($h['bits'] === 16) {
      $masks = [0x7c00, 0x03e0, 0x001f, 0];
    } else if ($h['bits'] === 32) {
      $masks = [0xff0000, 0xff00, 0xff, 0];
      // V3以上でアルファのマスクがあれば使う
      if ($dib >= 56) $masks[3] = unpack('V', substr($d, 66, 4))[1];
    }

    $entry = $dib === 12 ? 3 : 4;
    $colors = $h['bits'] <= 8 ? ($h['colors'] ?: 1 << $h['bits']) : 0;
    return [
      'offset' => $offset, 'dib' => $dib, 'width' => $h['width'], 'height' => $h['height'], 'bits' => $h['bits'],
      'comp' => $h['comp'], 'os2' => $os2, 'topDown' => $topDown, 'masks' => $masks,
      'colors' => min($colors, 256), 'palAt' => $palAt, 'entry' => $entry,
    ];
  }

  public function decode(string $data): Bitmap {
    $h = $this->header($data);
    $w = $h['width'];
    $ht = $h['height'];
    $comp = $h['comp'];
    $pixels = substr($data, $h['offset']);

    // 埋め込んだPNG・JPEG（OS/2の4はRLE24）
    if ($comp === self::PNG && !$h['os2']) return (new Png())->decode($pixels);
    if ($comp === self::JPEG && !$h['os2']) return (new Jpeg())->decode($pixels);
    if ($h['os2'] && $comp === 3) throw new \RuntimeException('OS/2のハフマン圧縮のBMPは未対応です。');

    // パレット => RGBA
    $lut = null;
    if ($h['bits'] <= 8) {
      $lut = [];
      for ($i = 0; $i < 256; $i++) {
        $e = $i < $h['colors'] ? substr($data, $h['palAt'] + $i * $h['entry'], 3) : '';
        $lut[chr($i)] = strlen($e) === 3 ? $e[2].$e[1].$e[0]."\xff" : "\0\0\0\xff";
      }
    }

    if ($comp === self::RLE8 || $comp === self::RLE4 || ($h['os2'] && $comp === 4)) {
      $rows = $this->rle($pixels, $w, $ht, $comp === self::RLE4 ? 4 : ($comp === self::RLE8 ? 8 : 24), $lut);
    } else {
      $stride = (($h['bits'] * $w + 31) >> 5) * 4;
      if (strlen($pixels) < $stride * $ht) throw new \RuntimeException('BMPの画素データが足りません。');
      $rows = [];
      $alphaSeen = false;
      for ($y = 0; $y < $ht; $y++) {
        $row = substr($pixels, $y * $stride, $stride);
        $rows[] = $this->row($row, $w, $h, $lut);
      }
      // 32ビットでアルファのマスクが無い場合：全部0なら不透明（Windowsはアルファを使わない）、それ以外は使う
      if ($h['bits'] === 32 && $h['masks'][3] === 0 && $comp !== self::BITFIELDS) {
        foreach ($rows as $y => $r) {
          $raw = substr($pixels, $y * $stride, $w * 4);
          for ($i = 3; $i < $w * 4; $i += 4) if ($raw[$i] !== "\0") {
            $alphaSeen = true;
            break 2;
          }
        }
        if ($alphaSeen) {
          foreach ($rows as $y => $r) {
            $raw = substr($pixels, $y * $stride, $w * 4);
            for ($i = 3; $i < $w * 4; $i += 4) $r[$i] = $raw[$i];
            $rows[$y] = $r;
          }
        }
      }
    }
    if (!$h['topDown']) $rows = array_reverse($rows);
    return new Bitmap($w, $ht, implode('', $rows));
  }

  /**
   * 圧縮していない1行をRGBAにする
   */
  private function row(string $row, int $w, array $h, ?array $lut): string {
    $bits = $h['bits'];
    if ($lut !== null) {
      if ($bits < 8) {
        static $unpack = [];
        if (!isset($unpack[$bits])) {
          $n = 8 / $bits;
          $mask = (1 << $bits) - 1;
          for ($b = 0; $b < 256; $b++) {
            $s = '';
            for ($k = $n - 1; $k >= 0; $k--) $s .= chr(($b >> ($k * $bits)) & $mask);
            $unpack[$bits][chr($b)] = $s;
          }
        }
        $row = strtr($row, $unpack[$bits]);
      }
      return strtr(substr($row, 0, $w), $lut);
    }
    if ($bits === 24) return preg_replace('/(.)(.)(.)/s', '$3$2$1'."\xff", substr($row, 0, $w * 3));
    $masks = $h['masks'];
    if ($bits === 32 && $masks === [0xff0000, 0xff00, 0xff, 0]) return preg_replace('/(.)(.)(.)./s', '$3$2$1'."\xff", substr($row, 0, $w * 4));
    if ($bits === 32 && $masks === [0xff0000, 0xff00, 0xff, 0xff000000]) return preg_replace('/(.)(.)(.)(.)/s', '$3$2$1$4', substr($row, 0, $w * 4));

    // ビットフィールド（16・32ビット）
    static $cache = [];
    $key = implode(',', $masks);
    if (!isset($cache[$key])) {
      $cache[$key] = array_map(function($m) {
        if ($m === 0) return null;
        $shift = 0;
        while ((($m >> $shift) & 1) === 0) $shift++;
        $max = $m >> $shift;
        return [$shift, $max];
      }, $masks);
    }
    $f = $cache[$key];
    $vals = array_values(unpack($bits === 16 ? 'v*' : 'V*', substr($row, 0, $w * ($bits >> 3))));
    $out = '';
    foreach ($vals as $v) {
      for ($c = 0; $c < 4; $c++) {
        if ($f[$c] === null) {
          $out .= $c === 3 ? "\xff" : "\0";
          continue;
        }
        [$shift, $max] = $f[$c];
        $out .= chr(intdiv((($v >> $shift) & $max) * 255 + ($max >> 1), $max));
      }
    }
    return $out;
  }

  /**
   * RLE8・RLE4・RLE24（OS/2）を展開する。飛ばした画素（デルタ、行・画像の終わり）は透明
   *
   * @return array  行（下から上）
   */
  private function rle(string $d, int $w, int $h, int $bits, ?array $lut): array {
    $rows = array_fill(0, $h, array_fill(0, $w, "\0\0\0\0"));
    $len = strlen($d);
    $p = 0;
    $x = $y = 0;
    $px = function(string $idx) use ($lut, $bits): string {
      return $bits === 24 ? $idx[2].$idx[1].$idx[0]."\xff" : $lut[$idx];
    };
    while ($p + 1 < $len && $y < $h) {
      $n = ord($d[$p]);
      $c = $d[$p + 1];
      $p += 2;
      if ($n > 0) {
        // 繰り返し
        if ($bits === 24) {
          $c = substr($d, $p - 1, 3);
          $p += 1;
          $v = $px($c);
          for ($i = 0; $i < $n && $x < $w; $i++) $rows[$y][$x++] = $v;
        } else if ($bits === 8) {
          $v = $px($c);
          for ($i = 0; $i < $n && $x < $w; $i++) $rows[$y][$x++] = $v;
        } else {
          $hi = $px(chr(ord($c) >> 4));
          $lo = $px(chr(ord($c) & 15));
          for ($i = 0; $i < $n && $x < $w; $i++) $rows[$y][$x++] = $i % 2 ? $lo : $hi;
        }
        continue;
      }
      $cmd = ord($c);
      if ($cmd === 0) {
        $x = 0;
        $y++;
      } else if ($cmd === 1) {
        break;
      } else if ($cmd === 2) {
        if ($p + 1 >= $len) break;
        $x += ord($d[$p]);
        $y += ord($d[$p + 1]);
        $p += 2;
      } else {
        // そのままの画素（2バイト境界に揃える）
        $bytes = $bits === 24 ? $cmd * 3 : ($bits === 8 ? $cmd : ($cmd + 1) >> 1);
        $chunk = substr($d, $p, $bytes);
        $p += $bytes + ($bytes & 1);
        for ($i = 0; $i < $cmd && $x < $w; $i++) {
          if ($bits === 24) $v = $px(substr($chunk, $i * 3, 3));
          else if ($bits === 8) $v = $px($chunk[$i] ?? "\0");
          else {
            $b = ord($chunk[$i >> 1] ?? "\0");
            $v = $px(chr($i % 2 ? $b & 15 : $b >> 4));
          }
          $rows[$y][$x++] = $v;
        }
      }
    }
    return array_map(fn($r) => implode('', $r), $rows);
  }

  /**
   * 画素をBMPにする
   *
   * 不透明で256色以下なら1・4・8ビットのパレット、不透明なら24ビット、
   * 透明があれば32ビット（BITMAPV4HEADERのアルファのマスク）。下から上の順。
   */
  public function encode(Bitmap $img, array $opt = []): string {
    $w = $img->width;
    $h = $img->height;
    $opaque = $img->isOpaque();
    $colors = [];
    if ($opaque) {
      for ($y = 0; $y < $h && count($colors) <= 256; $y++) $colors += array_flip(str_split($img->row($y), 4));
    }

    $palette = '';
    if ($opaque && count($colors) <= 256) {
      $n = count($colors);
      $bits = $n <= 2 ? 1 : ($n <= 16 ? 4 : 8);
      $map = [];
      foreach (array_keys($colors) as $i => $c) {
        $map[$c] = chr($i);
        $palette .= $c[2].$c[1].$c[0]."\0";
      }
      $dib = pack('VllvvVVllVV', 40, $w, $h, 1, $bits, self::RGB, 0, 2835, 2835, $n, 0);
    } else if ($opaque) {
      $bits = 24;
      $dib = pack('VllvvVVllVV', 40, $w, $h, 1, 24, self::RGB, 0, 2835, 2835, 0, 0);
    } else {
      $bits = 32;
      // V4：ビットフィールド（BGRA）＋sRGB
      $dib = pack('VllvvVVllVV', 108, $w, $h, 1, 32, self::BITFIELDS, 0, 2835, 2835, 0, 0)
           .pack('VVVV', 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000).'BGRs'.str_repeat("\0", 48);
    }

    $stride = (($bits * $w + 31) >> 5) * 4;
    $body = '';
    for ($y = $h - 1; $y >= 0; $y--) {
      $row = $img->row($y);
      $line = match ($bits) {
        24 => preg_replace('/(.)(.)(.)./s', '$3$2$1', $row),
        32 => preg_replace('/(.)(.)(.)(.)/s', '$3$2$1$4', $row),
        default => strtr($row, $map),
      };
      if ($bits < 8) {
        $per = 8 / $bits;
        $packed = '';
        foreach (str_split($line, $per) as $g) {
          $b = 0;
          for ($k = 0; $k < $per; $k++) $b = ($b << $bits) | ($k < strlen($g) ? ord($g[$k]) : 0);
          $packed .= chr($b);
        }
        $line = $packed;
      }
      $body .= str_pad($line, $stride, "\0");
    }
    $offset = 14 + strlen($dib) + strlen($palette);
    return 'BM'.pack('VvvV', $offset + strlen($body), 0, 0, $offset).$dib.$palette.$body;
  }
}