<?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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 */
namespace Std\Lib\Image;

/**
 * 画素データ（RGBA、各8ビット、左上から行の順）
 *
 * 全ての形式はこれに読み込み（decode）、これから書き出す（encode）。
 * アニメーション（APNG・GIF・WebP）はframesに、画面と同じ大きさに合成したフレームが入る。
 */
final class Bitmap {
  /** 読み込める最大の画素数（RGBAで約100MiB。それ以上はメモリが足りない事が多い） */
  public const MAX_PIXELS = 25000000;

  public int $width;
  public int $height;
  /** 画素（1画素4バイト：R, G, B, A） */
  public string $data;
  /** アニメーションのフレーム（[['bitmap' => Bitmap, 'delay' => ミリ秒], ...]）。静止画は空 */
  public array $frames = [];
  /** アニメーションの繰り返し回数（0 = 無限） */
  public int $loops = 0;

  public function __construct(int $width, int $height, ?string $data = null) {
    self::check($width, $height);
    $this->width = $width;
    $this->height = $height;
    $this->data = $data ?? str_repeat("\0\0\0\0", $width * $height);
    if (strlen($this->data) !== $width * $height * 4) throw new \InvalidArgumentException('画素データの大きさが合いません。');
  }

  /**
   * 画像の大きさを確認する（読み込む前に、壊れた・大き過ぎるファイルで落ちない様に）
   */
  public static function check(int $width, int $height): void {
    if ($width < 1 || $height < 1) throw new \RuntimeException("画像の大きさが不正です（{$width}x{$height}）。");
    if ($width * $height > self::MAX_PIXELS) throw new \RuntimeException("画像が大き過ぎます（{$width}x{$height}）。");
  }

  /** 1色で塗った画像 */
  public static function fill(int $width, int $height, int $r, int $g, int $b, int $a = 255): self {
    self::check($width, $height);
    return new self($width, $height, str_repeat(chr($r).chr($g).chr($b).chr($a), $width * $height));
  }

  /**
   * 画素を読む
   *
   * @return array  [r, g, b, a]
   */
  public function get(int $x, int $y): array {
    $o = ($y * $this->width + $x) * 4;
    return [ord($this->data[$o]), ord($this->data[$o + 1]), ord($this->data[$o + 2]), ord($this->data[$o + 3])];
  }

  public function set(int $x, int $y, int $r, int $g, int $b, int $a = 255): void {
    $o = ($y * $this->width + $x) * 4;
    $this->data[$o] = chr($r);
    $this->data[$o + 1] = chr($g);
    $this->data[$o + 2] = chr($b);
    $this->data[$o + 3] = chr($a);
  }

  /** 1行分の画素（RGBA） */
  public function row(int $y): string {
    return substr($this->data, $y * $this->width * 4, $this->width * 4);
  }

  /** 全ての画素が不透明か */
  public function isOpaque(): bool {
    $len = strlen($this->data);
    for ($i = 3; $i < $len; $i += 4) if ($this->data[$i] !== "\xff") return false;
    return true;
  }

  /** 全ての画素が灰色（R = G = B）か */
  public function isGray(): bool {
    $len = strlen($this->data);
    for ($i = 0; $i < $len; $i += 4) {
      if ($this->data[$i] !== $this->data[$i + 1] || $this->data[$i] !== $this->data[$i + 2]) return false;
    }
    return true;
  }

  /**
   * 別の画像を重ねる（はみ出した部分は切る）
   *
   * @param bool $blend  true：アルファで合成（over）、false：そのまま置き換える（source）
   */
  public function draw(Bitmap $src, int $dx, int $dy, bool $blend = true): void {
    $x0 = max(0, $dx);
    $x1 = min($this->width, $dx + $src->width);
    if ($x0 >= $x1) return;
    for ($sy = max(0, -$dy); $sy < $src->height && $sy + $dy < $this->height; $sy++) {
      $line = substr($src->data, ($sy * $src->width + $x0 - $dx) * 4, ($x1 - $x0) * 4);
      $at = (($sy + $dy) * $this->width + $x0) * 4;
      if ($blend) $line = self::over(substr($this->data, $at, strlen($line)), $line);
      $this->data = substr_replace($this->data, $line, $at, strlen($line));
    }
  }

  /** 範囲を1色にする */
  public function clear(int $x, int $y, int $w, int $h, int $r = 0, int $g = 0, int $b = 0, int $a = 0): void {
    $this->draw(self::fill(max(1, $w), max(1, $h), $r, $g, $b, $a), $x, $y, false);
  }

  /**
   * RGBAの列のアルファ合成（$fgを$bgの上に）
   */
  public static function over(string $bg, string $fg): string {
    // 殆どの画素は完全に不透明か透明なので、その場合は計算しない
    $len = strlen($fg);
    $out = $bg;
    for ($i = 0; $i < $len; $i += 4) {
      $fa = ord($fg[$i + 3]);
      if ($fa === 255) {
        $out[$i] = $fg[$i];
        $out[$i + 1] = $fg[$i + 1];
        $out[$i + 2] = $fg[$i + 2];
        $out[$i + 3] = "\xff";
      } else if ($fa !== 0) {
        $ba = ord($bg[$i + 3]);
        $oa = $fa + intdiv($ba * (255 - $fa) + 127, 255);
        for ($c = 0; $c < 3; $c++) {
          $v = (ord($fg[$i + $c]) * $fa * 255 + ord($bg[$i + $c]) * $ba * (255 - $fa)) / (255 * $oa);
          $out[$i + $c] = chr((int)round($v));
        }
        $out[$i + 3] = chr($oa);
      }
    }
    return $out;
  }

  public function copy(): self {
    $b = new self($this->width, $this->height, $this->data);
    $b->frames = $this->frames;
    $b->loops = $this->loops;
    return $b;
  }
}