<?php

namespace app\common\library\ps;

use think\Exception;

/**
 * 对比「标准原稿」和「色块标注图」，用色块外接矩形作为填写格。
 * 百分比坐标相对整张图，打印时再按纸张毫米还原。
 */
class MarkerDetector
{
    /**
     * @param string $cleanPath 标准展示图
     * @param string $markPath  涂了色块的图
     * @return array {width,height,cells:[{x,y,w,h,color,area}]}
     * @throws Exception
     */
    public static function detect($cleanPath, $markPath)
    {
        if (!function_exists('imagecreatefromstring')) {
            throw new Exception('当前 PHP 未开启 GD，无法识别色块');
        }
        @ini_set('memory_limit', '512M');
        $clean = self::loadImage($cleanPath);
        $mark = self::loadImage($markPath);
        $cw = imagesx($clean);
        $ch = imagesy($clean);
        $mw = imagesx($mark);
        $mh = imagesy($mark);
        if (abs($cw - $mw) > 2 || abs($ch - $mh) > 2) {
            if (abs(($ch / max($cw, 1)) - ($mh / max($mw, 1))) > 0.02) {
                imagedestroy($clean);
                imagedestroy($mark);
                throw new Exception('两张图的像素尺寸必须一致（请用同一张扫描件复制后涂色块）。标准图 '
                    . $cw . '×' . $ch . '，色块图 ' . $mw . '×' . $mh);
            }
            $resized = imagecreatetruecolor($cw, $ch);
            imagecopyresampled($resized, $mark, 0, 0, 0, 0, $cw, $ch, $mw, $mh);
            imagedestroy($mark);
            $mark = $resized;
        }

        $maxEdge = 900;
        $scale = min(1, $maxEdge / max($cw, $ch));
        $ww = max(1, (int)round($cw * $scale));
        $wh = max(1, (int)round($ch * $scale));
        $cWork = $clean;
        $mWork = $mark;
        if ($scale < 0.999) {
            $cWork = imagecreatetruecolor($ww, $wh);
            $mWork = imagecreatetruecolor($ww, $wh);
            imagecopyresampled($cWork, $clean, 0, 0, 0, 0, $ww, $wh, $cw, $ch);
            imagecopyresampled($mWork, $mark, 0, 0, 0, 0, $ww, $wh, $cw, $ch);
        }

        $mask = self::diffMask($cWork, $mWork);
        if ($cWork !== $clean) {
            imagedestroy($cWork);
        }
        if ($mWork !== $mark) {
            imagedestroy($mWork);
        }
        imagedestroy($clean);
        imagedestroy($mark);

        $minArea = max(30, (int)($ww * $wh * 0.00035));
        $blobs = self::connectedBoxes($mask, $ww, $wh, $minArea, 0, 0, $ww, $wh);
        $split = [];
        foreach ($blobs as $blob) {
            foreach (self::splitByValleys($blob, $mask, $ww, $wh, $minArea, 0) as $part) {
                $split[] = $part;
            }
        }
        $cells = [];
        $i = 0;
        foreach ($split as $blob) {
            $i++;
            $cells[] = [
                'id'    => 'c' . $i,
                'x'     => round($blob['x'] / $ww * 100, 2),
                'y'     => round($blob['y'] / $wh * 100, 2),
                'w'     => round($blob['w'] / $ww * 100, 2),
                'h'     => round($blob['h'] / $wh * 100, 2),
                'color' => $blob['color'],
                'area'  => $blob['area'],
            ];
        }
        usort($cells, function ($a, $b) {
            if (abs($a['y'] - $b['y']) > 2) {
                return $a['y'] < $b['y'] ? -1 : 1;
            }
            return $a['x'] < $b['x'] ? -1 : 1;
        });
        foreach ($cells as $idx => &$cell) {
            $cell['id'] = 'c' . ($idx + 1);
        }
        unset($cell);
        return [
            'width'  => $cw,
            'height' => $ch,
            'cells'  => $cells,
        ];
    }

    /**
     * @param string $path
     * @return resource
     * @throws Exception
     */
    protected static function loadImage($path)
    {
        if (!is_file($path)) {
            throw new Exception('图片不存在：' . $path);
        }
        $bin = @file_get_contents($path);
        if ($bin === false || $bin === '') {
            throw new Exception('图片无法读取');
        }
        $im = @imagecreatefromstring($bin);
        if (!$im) {
            throw new Exception('无法解析图片，请使用 JPG / PNG');
        }
        if (!imageistruecolor($im)) {
            $true = imagecreatetruecolor(imagesx($im), imagesy($im));
            imagefill($true, 0, 0, imagecolorallocate($true, 255, 255, 255));
            imagecopy($true, $im, 0, 0, 0, 0, imagesx($im), imagesy($im));
            imagedestroy($im);
            $im = $true;
        }
        return $im;
    }

    /**
     * @param resource $clean
     * @param resource $mark
     * @return string 0/1 packed rows
     */
    protected static function diffMask($clean, $mark)
    {
        $w = imagesx($clean);
        $h = imagesy($clean);
        $mask = str_repeat("\0", $w * $h);
        for ($y = 0; $y < $h; $y++) {
            $row = $y * $w;
            for ($x = 0; $x < $w; $x++) {
                $c = imagecolorat($clean, $x, $y);
                $m = imagecolorat($mark, $x, $y);
                $dr = (($c >> 16) & 0xFF) - (($m >> 16) & 0xFF);
                $dg = (($c >> 8) & 0xFF) - (($m >> 8) & 0xFF);
                $db = ($c & 0xFF) - ($m & 0xFF);
                if (($dr * $dr + $dg * $dg + $db * $db) < 1600) {
                    continue;
                }
                $mr = ($m >> 16) & 0xFF;
                $mg = ($m >> 8) & 0xFF;
                $mb = $m & 0xFF;
                $cr = ($c >> 16) & 0xFF;
                $cg = ($c >> 8) & 0xFF;
                $cb = $c & 0xFF;
                $markSat = max($mr, $mg, $mb) - min($mr, $mg, $mb);
                $cleanSat = max($cr, $cg, $cb) - min($cr, $cg, $cb);
                // 只要涂上去的鲜艳色，忽略原稿浅底色/JPEG 色差，否则页眉会把二维码和备注连成一块。
                if ($markSat < 80 || $markSat < $cleanSat + 35) {
                    continue;
                }
                $mask[$row + $x] = "\1";
            }
        }
        return $mask;
    }

    /**
     * @param string $mask
     * @param int    $w
     * @param int    $h
     * @param int    $minArea
     * @param int    $x0
     * @param int    $y0
     * @param int    $x1
     * @param int    $y1
     * @return array
     */
    protected static function connectedBoxes($mask, $w, $h, $minArea, $x0, $y0, $x1, $y1)
    {
        $seen = str_repeat("\0", $w * $h);
        $boxes = [];
        $maxBlobs = 80;
        $x0 = max(0, $x0);
        $y0 = max(0, $y0);
        $x1 = min($w, $x1);
        $y1 = min($h, $y1);
        for ($y = $y0; $y < $y1; $y++) {
            $row = $y * $w;
            for ($x = $x0; $x < $x1; $x++) {
                $i = $row + $x;
                if ($mask[$i] === "\0" || $seen[$i] === "\1") {
                    continue;
                }
                $box = self::flood($mask, $seen, $w, $h, $x, $y, $x0, $y0, $x1, $y1);
                if ($box && $box['area'] >= $minArea) {
                    $boxes[] = $box;
                    if (count($boxes) >= $maxBlobs) {
                        return $boxes;
                    }
                }
            }
        }
        return $boxes;
    }

    /**
     * 色块贴在一起（二维码右下角碰到备注条）时，沿投影空隙切开。
     * @param array  $box
     * @param string $mask
     * @param int    $w
     * @param int    $h
     * @param int    $minArea
     * @param int    $depth
     * @return array
     */
    protected static function splitByValleys(array $box, $mask, $w, $h, $minArea, $depth)
    {
        if ($depth >= 5) {
            return [$box];
        }
        $mask = self::clipBlobMask($mask, $w, $h, $box);
        $bw = (int)$box['w'];
        $bh = (int)$box['h'];
        $fill = $box['area'] / max(1, $bw * $bh);
        if ($fill >= 0.78 && $bw < $w * 0.45 && $bh < $h * 0.18) {
            return [$box];
        }
        if ($bw * $bh < $minArea * 4) {
            return [$box];
        }
        $rowHist = [];
        $colHist = [];
        $x0 = (int)$box['x'];
        $y0 = (int)$box['y'];
        for ($y = 0; $y < $bh; $y++) {
            $cnt = 0;
            $row = ($y0 + $y) * $w + $x0;
            for ($x = 0; $x < $bw; $x++) {
                if ($mask[$row + $x] === "\1") {
                    $cnt++;
                }
            }
            $rowHist[$y] = $cnt;
        }
        for ($x = 0; $x < $bw; $x++) {
            $cnt = 0;
            for ($y = 0; $y < $bh; $y++) {
                if ($mask[($y0 + $y) * $w + $x0 + $x] === "\1") {
                    $cnt++;
                }
            }
            $colHist[$x] = $cnt;
        }
        $rowGap = self::bestValley($rowHist, $minArea);
        $colGap = self::bestValley($colHist, $minArea);
        $axis = null;
        if ($rowGap && (!$colGap || $rowGap['score'] >= $colGap['score'])) {
            $axis = ['row', $rowGap['a'], $rowGap['b']];
        } elseif ($colGap) {
            $axis = ['col', $colGap['a'], $colGap['b']];
        }
        if (!$axis) {
            return [$box];
        }
        if ($axis[0] === 'row') {
            $rects = [
                [$x0, $y0, $bw, $axis[1]],
                [$x0, $y0 + $axis[2], $bw, $bh - $axis[2]],
            ];
        } else {
            $rects = [
                [$x0, $y0, $axis[1], $bh],
                [$x0 + $axis[2], $y0, $bw - $axis[2], $bh],
            ];
        }
        $parts = [];
        foreach ($rects as $rect) {
            if ($rect[2] < 4 || $rect[3] < 3) {
                continue;
            }
            $found = self::connectedBoxes($mask, $w, $h, $minArea, $rect[0], $rect[1], $rect[0] + $rect[2], $rect[1] + $rect[3]);
            foreach ($found as $child) {
                foreach (self::splitByValleys($child, $mask, $w, $h, $minArea, $depth + 1) as $part) {
                    $parts[] = $part;
                }
            }
        }
        return $parts ?: [$box];
    }

    /**
     * 只保留当前色块的像素，避免切开时把框内其它独立色块算进去。
     * @param string $mask
     * @param int    $w
     * @param int    $h
     * @param array  $box
     * @return string
     */
    protected static function clipBlobMask($mask, $w, $h, array $box)
    {
        $clip = str_repeat("\0", $w * $h);
        $seen = str_repeat("\0", $w * $h);
        $x0 = (int)$box['x'];
        $y0 = (int)$box['y'];
        $x1 = $x0 + (int)$box['w'];
        $y1 = $y0 + (int)$box['h'];
        $best = str_repeat("\0", $w * $h);
        $bestArea = 0;
        for ($sy = $y0; $sy < $y1; $sy++) {
            $row = $sy * $w;
            for ($sx = $x0; $sx < $x1; $sx++) {
                $si = $row + $sx;
                if ($mask[$si] === "\0" || $seen[$si] === "\1") {
                    continue;
                }
                $stack = [[$sx, $sy]];
                $cur = str_repeat("\0", $w * $h);
                $area = 0;
                while ($stack) {
                    list($x, $y) = array_pop($stack);
                    if ($x < $x0 || $y < $y0 || $x >= $x1 || $y >= $y1) {
                        continue;
                    }
                    $i = $y * $w + $x;
                    if ($mask[$i] === "\0" || $seen[$i] === "\1") {
                        continue;
                    }
                    $seen[$i] = "\1";
                    $cur[$i] = "\1";
                    $area++;
                    $stack[] = [$x + 1, $y];
                    $stack[] = [$x - 1, $y];
                    $stack[] = [$x, $y + 1];
                    $stack[] = [$x, $y - 1];
                }
                if ($area > $bestArea) {
                    $bestArea = $area;
                    $best = $cur;
                }
            }
        }
        return $best;
    }

    /**
     * @param array $hist
     * @param int   $minArea
     * @return array|null {a,b,score}
     */
    protected static function bestValley(array $hist, $minArea)
    {
        $n = count($hist);
        if ($n < 12) {
            return null;
        }
        $maxH = max($hist);
        if ($maxH < 8) {
            return null;
        }
        $limit = max(6, (int)round($maxH * 0.12));
        $best = null;
        $i = 1;
        while ($i < $n - 1) {
            if ($hist[$i] > $limit) {
                $i++;
                continue;
            }
            $a = $i;
            while ($i < $n - 1 && $hist[$i] <= $limit) {
                $i++;
            }
            $b = $i;
            if ($b - $a < 1) {
                continue;
            }
            if ($a < 2 || $b > $n - 2) {
                continue;
            }
            $left = 0;
            for ($k = 0; $k < $a; $k++) {
                $left += $hist[$k];
            }
            $right = 0;
            for ($k = $b; $k < $n; $k++) {
                $right += $hist[$k];
            }
            if ($left < $minArea || $right < $minArea) {
                continue;
            }
            $score = ($b - $a) * min($left, $right);
            if (!$best || $score > $best['score']) {
                $best = ['a' => $a, 'b' => $b, 'score' => $score];
            }
        }
        return $best;
    }

    /**
     * @param string $mask
     * @param string $seen
     * @param int    $w
     * @param int    $h
     * @param int    $sx
     * @param int    $sy
     * @param int    $x0
     * @param int    $y0
     * @param int    $x1
     * @param int    $y1
     * @return array|null
     */
    protected static function flood($mask, &$seen, $w, $h, $sx, $sy, $x0, $y0, $x1, $y1)
    {
        $stack = [[$sx, $sy]];
        $minX = $maxX = $sx;
        $minY = $maxY = $sy;
        $area = 0;
        $limit = $w * $h;
        while ($stack) {
            list($x, $y) = array_pop($stack);
            if ($x < $x0 || $y < $y0 || $x >= $x1 || $y >= $y1) {
                continue;
            }
            $i = $y * $w + $x;
            if ($mask[$i] === "\0" || $seen[$i] === "\1") {
                continue;
            }
            $seen[$i] = "\1";
            $area++;
            if ($area > $limit) {
                break;
            }
            if ($x < $minX) {
                $minX = $x;
            }
            if ($x > $maxX) {
                $maxX = $x;
            }
            if ($y < $minY) {
                $minY = $y;
            }
            if ($y > $maxY) {
                $maxY = $y;
            }
            $stack[] = [$x + 1, $y];
            $stack[] = [$x - 1, $y];
            $stack[] = [$x, $y + 1];
            $stack[] = [$x, $y - 1];
        }
        if ($area < 1) {
            return null;
        }
        $bw = $maxX - $minX + 1;
        $bh = $maxY - $minY + 1;
        if ($bw < 4 || $bh < 3) {
            return null;
        }
        return [
            'x'     => $minX,
            'y'     => $minY,
            'w'     => $bw,
            'h'     => $bh,
            'area'  => $area,
            'color' => '#ffff00',
        ];
    }
}