:octocat: integrate reader into QRCode, extract LuminanceSourceInterface

src/Decoder/LuminanceSourceAbstract.php

@@ -0,0 +1,102 @@
+<?php
+/**
+ * Class LuminanceSourceAbstract
+ *
+ * @created      24.01.2021
+ * @author       ZXing Authors
+ * @author       Smiley <smiley@chillerlan.net>
+ * @copyright    2021 Smiley
+ * @license      Apache-2.0
+ */
+
+namespace chillerlan\QRCode\Decoder;
+
+use InvalidArgumentException;
+use function array_slice, array_splice, file_exists, is_file, is_readable, realpath;
+
+/**
+ * The purpose of this class hierarchy is to abstract different bitmap implementations across
+ * platforms into a standard interface for requesting greyscale luminance values. The interface
+ * only provides immutable methods; therefore crop and rotation create copies. This is to ensure
+ * that one Reader does not modify the original luminance source and leave it in an unknown state
+ * for other Readers in the chain.
+ *
+ * @author dswitkin@google.com (Daniel Switkin)
+ */
+abstract class LuminanceSourceAbstract implements LuminanceSourceInterface{
+
+	protected array $luminances;
+	protected int   $width;
+	protected int   $height;
+
+	/**
+	 *
+	 */
+	public function __construct(int $width, int $height){
+		$this->width  = $width;
+		$this->height = $height;
+		// In order to measure pure decoding speed, we convert the entire image to a greyscale array
+		// up front, which is the same as the Y channel of the YUVLuminanceSource in the real app.
+		$this->luminances = [];
+	}
+
+	/** @inheritDoc */
+	public function getMatrix():array{
+		return $this->luminances;
+	}
+
+	/** @inheritDoc */
+	public function getWidth():int{
+		return $this->width;
+	}
+
+	/** @inheritDoc */
+	public function getHeight():int{
+		return $this->height;
+	}
+
+	/** @inheritDoc */
+	public function getRow(int $y):array{
+
+		if($y < 0 || $y >= $this->getHeight()){
+			throw new InvalidArgumentException('Requested row is outside the image: '.$y);
+		}
+
+		$arr = [];
+
+		array_splice($arr, 0, $this->width, array_slice($this->luminances, $y * $this->width, $this->width));
+
+		return $arr;
+	}
+
+	/**
+	 *
+	 */
+	protected function setLuminancePixel(int $r, int $g, int $b):void{
+		$this->luminances[] = $r === $g && $g === $b
+			// Image is already greyscale, so pick any channel.
+			? $r // (($r + 128) % 256) - 128;
+			// Calculate luminance cheaply, favoring green.
+			: ($r + 2 * $g + $b) / 4; // (((($r + 2 * $g + $b) / 4) + 128) % 256) - 128;
+	}
+
+	/**
+	 *
+	 */
+	protected static function checkFile(string $path):string{
+		$path = trim($path);
+
+		if(!file_exists($path) || !is_file($path) || !is_readable($path)){
+			throw new InvalidArgumentException('invalid file: '.$path);
+		}
+
+		$realpath = realpath($path);
+
+		if($realpath === false){
+			throw new InvalidArgumentException('unable to resolve path: '.$path);
+		}
+
+		return $realpath;
+	}
+
+}