<?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,
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         you created the original Software.
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         incorporating it, must not be used for censorship or to suppress freedom of
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         limited to:
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           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
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 */
namespace Std\Lib\Image;

/**
 * TGA（Truevision TGA 1.0・2.0）
 *
 * 種類：1（パレット）、2（トゥルーカラー）、3（グレースケール）と、そのRLE（9・10・11）
 * 画素：8・15・16・24・32ビット（グレースケールは8ビット又は16ビット＝灰色＋アルファ）
 * パレット：15・16・24・32ビット。原点：左下（既定）・左上・右上・右下
 * アルファ：属性ビット（記述子の下4ビット）と、TGA 2.0の拡張領域の属性の種類（無し・事前乗算）
 */
class Targa implements ImageInterface {
  private const TYPES = [
    1 => 'UNCOMPRESSED COLOR-MAPPED IMAGE',
    2 => 'UNCOMPRESSED TRUE COLOR IMAGE',
    3 => 'UNCOMPRESSED GRAYSCALE IMAGE',
    9 => 'RUN-LENGTH ENCODED COLOR-MAPPED IMAGE',
    10 => 'RUN-LENGTH ENCODED TRUE-COLOR IMAGE',
    11 => 'RUN-LENGTH ENCODED GRAYSCALE IMAGE',
  ];
  private const FOOTER = "TRUEVISION-XFILE.\0";

  public function parse(string $file): \stdClass {
    $d = (string)file_get_contents($file);
    $h = $this->header($d);
    return (object)[
      'width' => $h['width'],
      'height' => $h['height'],
      'imageTypeByte' => $h['type'],
      'imageType' => self::TYPES[$h['type']],
      'bitDepth' => $h['depth'],
      'colorMapType' => $h['cmType'],
      'colorMapLength' => $h['cmLength'],
      'colorMapBits' => $h['cmBits'],
      'x' => $h['x'],
      'y' => $h['y'],
      'isTopToBottom' => $h['top'],
      'isRightToLeft' => $h['right'],
      'alphaBits' => $h['alphaBits'],
      'hasAlpha' => $h['alpha'],
      'imageId' => $h['id'],
      'version' => $h['v2'] ? 2 : 1,
    ];
  }

  /**
   * ヘッダー（とTGA 2.0のフッター・拡張領域）を読む
   */
  private function header(string $d): array {
    if (strlen($d) < 18) throw new \RuntimeException('TGAではありません。');
    $h = unpack('CidLen/CcmType/Ctype/vcmFirst/vcmLength/CcmBits/vx/vy/vwidth/vheight/Cdepth/Cdesc', $d);
    if (!isset(self::TYPES[$h['type']])) throw new \RuntimeException("未対応のTGAの種類です（{$h['type']}）。");
    $okDepth = match ($h['type'] & 7) {
      1 => in_array($h['depth'], [8, 16], true) && $h['cmType'] === 1,
      2 => in_array($h['depth'], [15, 16, 24, 32], true),
      3 => in_array($h['depth'], [8, 16], true),
    };
    if (!$okDepth || ($h['cmType'] === 1 && !in_array($h['cmBits'], [15, 16, 24, 32], true))) {
      throw new \RuntimeException('TGAのビット深さが不正です。');
    }
    Bitmap::check($h['width'], $h['height']);

    $alphaBits = $h['desc'] & 0x0f;
    // TGA 2.0：拡張領域の「属性の種類」（0 = アルファ無し、1・2 = 未定義、3 = アルファ、4 = 事前乗算したアルファ）
    $v2 = strlen($d) >= 44 && substr($d, -18) === self::FOOTER;
    $attr = null;
    if ($v2) {
      $ext = unpack('V', substr($d, -26, 4))[1];
      if ($ext > 0 && $ext + 495 <= strlen($d) - 26 && unpack('v', substr($d, $ext, 2))[1] >= 495) $attr = ord($d[$ext + 494]);
    }
    $alpha = $alphaBits > 0 && ($attr === null || $attr >= 3);
    // パレットの画像は、パレットの項目のアルファを使う
    if (($h['type'] & 7) === 1) $alpha = $h['cmBits'] === 32 || ($h['cmBits'] === 16 && $alphaBits > 0);
    if (($h['type'] & 7) === 3 && $h['depth'] === 16) $alpha = true;

    return $h + [
      'id' => substr($d, 18, $h['idLen']),
      'top' => ($h['desc'] & 0x20) !== 0,
      'right' => ($h['desc'] & 0x10) !== 0,
      'alphaBits' => $alphaBits,
      'alpha' => $alpha,
      'premultiplied' => $attr === 4,
      'v2' => $v2,
    ];
  }

  public function decode(string $data): Bitmap {
    $h = $this->header($data);
    $w = $h['width'];
    $ht = $h['height'];
    $kind = $h['type'] & 7;
    $pos = 18 + $h['idLen'];

    // パレット
    $lut = null;
    if ($h['cmType'] === 1) {
      $eb = ($h['cmBits'] + 7) >> 3;
      $cm = substr($data, $pos, $h['cmLength'] * $eb);
      $pos += $h['cmLength'] * $eb;
      if ($kind === 1) {
        $lut = [];
        $n = $h['depth'] === 16 ? 65536 : 256;
        $entries = str_split($cm, $eb);
        foreach ($entries as $i => $e) $lut[$h['cmFirst'] + $i] = $this->pixel($e, $h['cmBits'], $h['alpha']);
      }
    }

    $bpp = ($h['depth'] + 7) >> 3;
    $count = $w * $ht;
    if ($h['type'] >= 9) {
      $raw = $this->unrle($data, $pos, $count, $bpp);
    } else {
      $raw = substr($data, $pos, $count * $bpp);
      if (strlen($raw) < $count * $bpp) throw new \RuntimeException('TGAの画素データが足りません。');
    }

    // RGBAにする
    if ($kind === 1) {
      $idx = $h['depth'] === 16 ? array_values(unpack('v*', $raw)) : array_values(unpack('C*', $raw));
      $black = "\0\0\0".($h['alpha'] ? "\0" : "\xff");
      $px = implode('', array_map(fn($i) => $lut[$i] ?? $black, $idx));
    } else if ($kind === 3) {
      $px = $h['depth'] === 8 ? preg_replace('/(.)/s', '$1$1$1'."\xff", $raw) : preg_replace('/(.)(.)/s', '$1$1$1$2', $raw);
    } else if ($h['depth'] === 24) {
      $px = preg_replace('/(.)(.)(.)/s', '$3$2$1'."\xff", $raw);
    } else if ($h['depth'] === 32) {
      $px = $h['alpha'] ? preg_replace('/(.)(.)(.)(.)/s', '$3$2$1$4', $raw) : preg_replace('/(.)(.)(.)./s', '$3$2$1'."\xff", $raw);
    } else {
      $alpha = $h['alpha'] && $h['depth'] === 16;
      $px = implode('', array_map(fn($p) => $this->pixel($p, 16, $alpha), str_split($raw, 2)));
    }

    if ($h['premultiplied']) $px = $this->unpremultiply($px);

    // 向き（既定は左下が原点）
    $rows = str_split($px, $w * 4);
    if (!$h['top']) $rows = array_reverse($rows);
    if ($h['right']) $rows = array_map(fn($r) => implode('', array_reverse(str_split($r, 4))), $rows);
    return new Bitmap($w, $ht, implode('', $rows));
  }

  /**
   * パレットの項目又は15・16ビットの画素をRGBAにする
   */
  private function pixel(string $p, int $bits, bool $alpha): string {
    if ($bits === 24) return $p[2].$p[1].$p[0]."\xff";
    if ($bits === 32) return $p[2].$p[1].$p[0].($alpha ? $p[3] : "\xff");
    // A1R5G5B5（リトルエンディアン）
    $v = ord($p[0]) | (ord($p[1] ?? "\0") << 8);
    $c = fn($x) => chr(($x << 3) | ($x >> 2));
    $a = $bits === 16 && $alpha ? ($v & 0x8000 ? "\xff" : "\0") : "\xff";
    return $c(($v >> 10) & 31).$c(($v >> 5) & 31).$c($v & 31).$a;
  }

  /**
   * RLEを展開する（パケットが行を跨いでも良い）
   */
  private function unrle(string $d, int $pos, int $count, int $bpp): string {
    $out = '';
    $n = 0;
    $len = strlen($d);
    while ($n < $count) {
      if ($pos >= $len) throw new \RuntimeException('TGAのRLEデータが足りません。');
      $hdr = ord($d[$pos++]);
      $k = ($hdr & 0x7f) + 1;
      if ($hdr & 0x80) {
        $out .= str_repeat(substr($d, $pos, $bpp), $k);
        $pos += $bpp;
      } else {
        $out .= substr($d, $pos, $k * $bpp);
        $pos += $k * $bpp;
      }
      $n += $k;
    }
    return substr($out, 0, $count * $bpp);
  }

  private function unpremultiply(string $px): string {
    $len = strlen($px);
    for ($i = 0; $i < $len; $i += 4) {
      $a = ord($px[$i + 3]);
      if ($a === 0 || $a === 255) continue;
      for ($c = 0; $c < 3; $c++) $px[$i + $c] = chr(min(255, intdiv(ord($px[$i + $c]) * 255 + ($a >> 1), $a)));
    }
    return $px;
  }

  /**
   * 画素をTGAにする（RLEのトゥルーカラー、不透明なら24ビット、それ以外は32ビット、左上が原点、TGA 2.0のフッター付き）
   *
   * @param array $opt  rle：false で圧縮しない
   */
  public function encode(Bitmap $img, array $opt = []): string {
    $alpha = !$img->isOpaque();
    $bpp = $alpha ? 4 : 3;
    $rle = $opt['rle'] ?? true;
    $raw = $alpha ? preg_replace('/(.)(.)(.)(.)/s', '$3$2$1$4', $img->data) : preg_replace('/(.)(.)(.)./s', '$3$2$1', $img->data);
    $header = pack('CCCvvCvvvvCC', 0, 0, $rle ? 10 : 2, 0, 0, 0, 0, 0, $img->width, $img->height, $bpp * 8, 0x20 | ($alpha ? 8 : 0));
    $body = $rle ? $this->rle($raw, $img->width, $bpp) : $raw;
    return $header.$body.pack('VV', 0, 0).self::FOOTER;
  }

  /**
   * RLEにする（TGA 2.0の推奨通り、パケットは行を跨がない）
   */
  private function rle(string $raw, int $w, int $bpp): string {
    $out = '';
    foreach (str_split($raw, $w * $bpp) as $row) {
      $px = str_split($row, $bpp);
      $n = count($px);
      $i = 0;
      while ($i < $n) {
        // 同じ画素の繰り返し
        $j = $i + 1;
        while ($j < $n && $j - $i < 128 && $px[$j] === $px[$i]) $j++;
        if ($j - $i >= 2) {
          $out .= chr(0x80 | ($j - $i - 1)).$px[$i];
          $i = $j;
          continue;
        }
        // 繰り返さない画素（次の繰り返しの前まで）
        $j = $i + 1;
        while ($j < $n && $j - $i < 128 && !($j + 1 < $n && $px[$j] === $px[$j + 1])) $j++;
        $out .= chr($j - $i - 1).implode('', array_slice($px, $i, $j - $i));
        $i = $j;
      }
    }
    return $out;
  }
}