<?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**
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    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
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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;

/**
 * WebP（RIFFの入れ物）
 *
 * 読み込み：非可逆（VP8）、可逆（VP8L）、拡張形式（VP8X）のアルファ（ALPH、無圧縮・可逆、全てのフィルター）、
 * アニメーション（ANIM・ANMF、合成方法と廃棄方法、繰り返し回数）。
 * 書き出し：既定は非可逆（quality、アルファがあればALPHを可逆圧縮）、lossless => trueなら可逆。framesがあればアニメーション。
 */
class Webp implements ImageInterface {
  public function parse(string $file): \stdClass {
    $d = (string)file_get_contents($file);
    $chunks = self::chunks($d);
    $info = (object)['width' => 0, 'height' => 0, 'compression' => null, 'hasAlpha' => false, 'animated' => false, 'frames' => 1, 'loops' => 0, 'icc' => false, 'exif' => false, 'xmp' => false];
    $image = null;
    foreach ($chunks as [$id, $body]) {
      if ($id === 'VP8X') {
        if (strlen($body) < 10) throw new \RuntimeException('VP8Xチャンクが短過ぎます。');
        $f = ord($body[0]);
        $info->width = 1 + self::u24($body, 4);
        $info->height = 1 + self::u24($body, 7);
        $info->hasAlpha = (bool)($f & 0x10);
        $info->animated = (bool)($f & 0x02);
        $info->icc = (bool)($f & 0x20);
        $info->exif = (bool)($f & 0x08);
        $info->xmp = (bool)($f & 0x04);
      } else if ($id === 'ANIM' && strlen($body) >= 6) {
        $info->loops = unpack('v', substr($body, 4, 2))[1];
      } else if ($id === 'ANMF') {
        $image ??= self::chunks($body, 16)[0] ?? null;
      } else if ($id === 'VP8 ' || $id === 'VP8L') {
        $image ??= [$id, $body];
      }
    }
    if ($info->animated) $info->frames = count(array_filter($chunks, fn($c) => $c[0] === 'ANMF'));
    if ($image !== null) {
      [$id, $body] = $image;
      $info->compression = $id === 'VP8L' ? 'VP8L' : 'VP8';
      if ($chunks[0][0] !== 'VP8X') {
        if ($id === 'VP8L' && strlen($body) >= 5) {
          $b = unpack('V', substr($body, 1, 4))[1];
          $info->width = ($b & 0x3fff) + 1;
          $info->height = (($b >> 14) & 0x3fff) + 1;
          $info->hasAlpha = (bool)(($b >> 28) & 1);
        } else if ($id === 'VP8 ' && strlen($body) >= 10) {
          $info->width = unpack('v', substr($body, 6, 2))[1] & 0x3fff;
          $info->height = unpack('v', substr($body, 8, 2))[1] & 0x3fff;
        }
      }
    }
    return $info;
  }

  /**
   * RIFFのチャンク
   *
   * @param int $pos  最初のチャンクの位置（ファイルなら12、ANMFの中なら16）
   * @return array  [[ID, 中身], ...]
   */
  private static function chunks(string $d, int $pos = 12): array {
    $end = strlen($d);
    if ($pos === 12) {
      if (strlen($d) < 12 || !str_starts_with($d, 'RIFF') || substr($d, 8, 4) !== 'WEBP') throw new \RuntimeException('WebPではありません。');
      $end = min($end, 8 + unpack('V', substr($d, 4, 4))[1]);
    }
    $out = [];
    while ($pos + 8 <= $end) {
      $id = substr($d, $pos, 4);
      $size = unpack('V', substr($d, $pos + 4, 4))[1];
      if ($pos + 8 + $size > $end) throw new \RuntimeException("WebPの{$id}チャンクが途中で切れています。");
      $out[] = [$id, substr($d, $pos + 8, $size)];
      $pos += 8 + $size + ($size & 1);
    }
    return $out;
  }

  private static function u24(string $s, int $o): int {
    return ord($s[$o]) | (ord($s[$o + 1]) << 8) | (ord($s[$o + 2]) << 16);
  }

  public function decode(string $data): Bitmap {
    $chunks = self::chunks($data);
    $first = $chunks[0][0] ?? '';
    if ($first === 'VP8 ' || $first === 'VP8L') return self::still($chunks);
    if ($first !== 'VP8X' || strlen($chunks[0][1]) < 10) throw new \RuntimeException('WebPの画像がありません。');
    $body = $chunks[0][1];
    $cw = 1 + self::u24($body, 4);
    $ch = 1 + self::u24($body, 7);
    Bitmap::check($cw, $ch);
    if (!(ord($body[0]) & 0x02)) return self::still(array_slice($chunks, 1), $cw, $ch);

    // アニメーション：透明な画面にフレームを順に重ねる（背景色はブラウザと同じく使わない）
    $loops = 0;
    $canvas = new Bitmap($cw, $ch);
    $img = null;
    $dispose = null;
    foreach ($chunks as [$id, $body]) {
      if ($id === 'ANIM' && strlen($body) >= 6) $loops = unpack('v', substr($body, 4, 2))[1];
      if ($id !== 'ANMF') continue;
      if (strlen($body) < 16) throw new \RuntimeException('ANMFチャンクが短過ぎます。');
      $x = 2 * self::u24($body, 0);
      $y = 2 * self::u24($body, 3);
      $fw = 1 + self::u24($body, 6);
      $fh = 1 + self::u24($body, 9);
      $flags = ord($body[15]);
      if ($x + $fw > $cw || $y + $fh > $ch) throw new \RuntimeException('WebPのフレームが画面からはみ出しています。');
      if ($dispose !== null) $canvas->clear(...$dispose);
      $canvas->draw(self::still(self::chunks($body, 16), $fw, $fh), $x, $y, !($flags & 0x02));
      $img ??= $canvas->copy();
      $img->frames[] = ['bitmap' => $canvas->copy(), 'delay' => self::u24($body, 12)];
      $dispose = $flags & 0x01 ? [$x, $y, $fw, $fh] : null;
    }
    if ($img === null) throw new \RuntimeException('WebPのアニメーションにフレームがありません。');
    if (count($img->frames) < 2) $img->frames = [];
    else $img->loops = $loops;
    return $img;
  }

  /**
   * 1枚の画像（VP8L、又はALPHとVP8）
   *
   * @param int|null $w  期待する幅と丈（VP8XやANMFの大きさ）
   */
  private static function still(array $chunks, ?int $w = null, ?int $h = null): Bitmap {
    $alpha = null;
    foreach ($chunks as [$id, $body]) {
      if ($id === 'ALPH') {
        $alpha ??= $body;
      } else if ($id === 'VP8L') {
        [$iw, $ih, $argb] = (new Vp8l())->decode($body);
        $rgba = self::rgba($argb);
        break;
      } else if ($id === 'VP8 ') {
        [$iw, $ih, $rgba] = (new Vp8())->decode($body);
        if ($alpha !== null) $rgba = self::applyAlpha($rgba, $alpha, $iw, $ih);
        break;
      }
    }
    if (!isset($rgba)) throw new \RuntimeException('WebPの画像データがありません。');
    if ($w !== null && ($iw !== $w || $ih !== $h)) throw new \RuntimeException('WebPの画像の大きさが合いません。');
    return new Bitmap($iw, $ih, $rgba);
  }

  /** ARGB（ビッグエンディアン）の列をRGBAにする */
  private static function rgba(string $argb): string {
    $out = '';
    for ($o = 0, $n = strlen($argb); $o < $n; $o += 16384) {
      $px = unpack('N*', substr($argb, $o, 16384));
      foreach ($px as $i => $v) $px[$i] = (($v << 8) & 0xffffffff) | ($v >> 24);
      $out .= pack('N*', ...$px);
    }
    return $out;
  }

  /**
   * ALPHチャンクのアルファを画素に入れる
   */
  private static function applyAlpha(string $rgba, string $alph, int $w, int $h): string {
    if ($alph === '') throw new \RuntimeException('ALPHチャンクが空です。');
    $hdr = ord($alph[0]);
    $n = $w * $h;
    if (($hdr & 3) === 0) {
      $a = substr($alph, 1, $n);
      if (strlen($a) < $n) throw new \RuntimeException('ALPHチャンクが途中で切れています。');
    } else if (($hdr & 3) === 1) {
      // 可逆圧縮：緑がアルファ
      $argb = (new Vp8l())->decodeImage(substr($alph, 1), $w, $h);
      $a = '';
      for ($i = 2, $len = strlen($argb); $i < $len; $i += 4) $a .= $argb[$i];
    } else {
      throw new \RuntimeException('未対応のALPHの圧縮方法です。');
    }
    $filter = ($hdr >> 2) & 3;
    if ($filter) $a = self::unfilter($a, $w, $h, $filter);
    for ($i = 0; $i < $n; $i++) $rgba[$i * 4 + 3] = $a[$i];
    return $rgba;
  }

  /**
   * アルファのフィルターを戻す（1：左、2：上、3：勾配。1行目は左、左端は上から）
   */
  private static function unfilter(string $a, int $w, int $h, int $filter): string {
    $out = '';
    $prev = null;
    for ($y = 0; $y < $h; $y++) {
      $row = array_values(unpack('C*', substr($a, $y * $w, $w)));
      if ($prev === null) {
        $left = 0;
        for ($x = 0; $x < $w; $x++) $row[$x] = $left = ($row[$x] + $left) & 255;
      } else if ($filter === 1) {
        $left = $prev[0];
        for ($x = 0; $x < $w; $x++) $row[$x] = $left = ($row[$x] + $left) & 255;
      } else if ($filter === 2) {
        for ($x = 0; $x < $w; $x++) $row[$x] = ($row[$x] + $prev[$x]) & 255;
      } else {
        $left = $topLeft = $prev[0];
        for ($x = 0; $x < $w; $x++) {
          $g = $left + $prev[$x] - $topLeft;
          $left = $row[$x] = ($row[$x] + ($g < 0 ? 0 : ($g > 255 ? 255 : $g))) & 255;
          $topLeft = $prev[$x];
        }
      }
      $out .= pack('C*', ...$row);
      $prev = $row;
    }
    return $out;
  }

  /**
   * @param array $opt  lossless（既定false）、quality（非可逆、0～100、既定80）、filter・sharpness・partitions（非可逆の細かい設定）
   */
  public function encode(Bitmap $img, array $opt = []): string {
    $lossless = (bool)($opt['lossless'] ?? false);
    if (!$lossless && ($img->width > 16383 || $img->height > 16383)) throw new \RuntimeException('非可逆のWebPは16383x16383までです。');
    if ($img->width > 16384 || $img->height > 16384) throw new \RuntimeException('WebPは16384x16384までです。');
    if (!$img->frames) {
      $alpha = !$img->isOpaque();
      $body = self::image($img, $lossless, $alpha, $opt);
      if ($lossless || !$alpha) return self::riff($body);
      return self::riff(self::vp8x($img, 0x10).$body);
    }
    $alpha = false;
    foreach ($img->frames as $f) $alpha = $alpha || !$f['bitmap']->isOpaque();
    $out = self::vp8x($img, 0x02 | ($alpha ? 0x10 : 0));
    // 背景色（白、BGRA）と繰り返し回数
    $out .= self::chunk('ANIM', "\xff\xff\xff\xff".pack('v', min(65535, $img->loops)));
    foreach ($img->frames as $f) {
      $b = $f['bitmap'];
      if ($b->width !== $img->width || $b->height !== $img->height) throw new \InvalidArgumentException('フレームの大きさが画像と違います。');
      // 毎回画面全体を置き換える（合成しない、廃棄しない）
      $hdr = "\0\0\0\0\0\0".substr(pack('V', $b->width - 1), 0, 3).substr(pack('V', $b->height - 1), 0, 3).substr(pack('V', max(0, min(0xffffff, (int)$f['delay']))), 0, 3)."\x02";
      $out .= self::chunk('ANMF', $hdr.self::image($b, $lossless, !$b->isOpaque(), $opt));
    }
    return self::riff($out);
  }

  /** 1枚の画像のチャンク（VP8L、VP8、又はALPHとVP8） */
  private static function image(Bitmap $b, bool $lossless, bool $alpha, array $opt): string {
    if ($lossless) {
      $px = [];
      foreach (unpack('N*', $b->data) as $v) $px[] = (($v & 255) << 24) | ($v >> 8);
      return self::chunk('VP8L', (new Vp8l())->encode($px, $b->width, $b->height, $alpha));
    }
    $out = '';
    if ($alpha) {
      $a = [];
      foreach (unpack('N*', $b->data) as $v) $a[] = ($v & 255) << 8;
      // 可逆圧縮、フィルター無し
      $out .= self::chunk('ALPH', "\x01".(new Vp8l())->encodeImage($a, $b->width, $b->height));
    }
    return $out.self::chunk('VP8 ', (new Vp8())->encode($b->data, $b->width, $b->height, $opt));
  }

  private static function vp8x(Bitmap $img, int $flags): string {
    return self::chunk('VP8X', chr($flags)."\0\0\0".substr(pack('V', $img->width - 1), 0, 3).substr(pack('V', $img->height - 1), 0, 3));
  }

  private static function chunk(string $id, string $body): string {
    return $id.pack('V', strlen($body)).$body.(strlen($body) & 1 ? "\0" : '');
  }

  private static function riff(string $body): string {
    return 'RIFF'.pack('V', 4 + strlen($body)).'WEBP'.$body;
  }
}