Move Floyd-Steinberg dithering logic to its own class.

Author: andersonls

src/Commands/Dithering.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace Zpl\Commands;
+
+use GdImage;
+
+class Dithering
+{
+    /**
+     * Apply Floyd 6Steinberg dithering to the given image in-place.
+     */
+    public static function apply(GdImage $im, int $threshold = 128): void
+    {
+        $w = imagesx($im);
+        $h = imagesy($im);
+
+        $gray = [];
+        for ($y = 0; $y < $h; $y++) {
+            $base = $y * $w;
+            for ($x = 0; $x < $w; $x++) {
+                $rgb = imagecolorat($im, $x, $y);
+                $r = ($rgb >> 16) & 0xFF;
+                $g = ($rgb >> 8) & 0xFF;
+                $b = $rgb & 0xFF;
+                $gray[$base + $x] = ($r * 299 + $g * 587 + $b * 114) / 1000;
+            }
+        }
+
+        $fs = [[1, 0, 7 / 16], [-1, 1, 3 / 16], [0, 1, 5 / 16], [1, 1, 1 / 16]];
+        for ($y = 0; $y < $h; $y++) {
+            $base = $y * $w;
+            for ($x = 0; $x < $w; $x++) {
+                $i = $base + $x;
+                $old = $gray[$i];
+                $gray[$i] = $new = $old < $threshold ? 0 : 255;
+                $error = $old - $new;
+                foreach ($fs as $m) {
+                    $nx = $x + $m[0];
+                    $ny = $y + $m[1];
+                    if ($nx >= 0 && $nx < $w && $ny < $h) {
+                        $ni = $ny * $w + $nx;
+                        $v = $gray[$ni] + $error * $m[2];
+                        $gray[$ni] = $v <= 0 ? 0 : (min($v, 255));
+                    }
+                }
+            }
+        }
+
+        for ($y = 0; $y < $h; $y++) {
+            $base = $y * $w;
+            for ($x = 0; $x < $w; $x++) {
+                $v = (int) $gray[$base + $x];
+                imagesetpixel($im, $x, $y, ($v << 16) | ($v << 8) | $v);
+            }
+        }
+    }
+}

src/Commands/GraphicField.php

@@ -59,7 +59,7 @@ public function encodeImage(string $image, int $width, bool $compressData = true
 
         $im = $resized;
         if ($dithering) {
-            $this->applyDithering($im);
+            Dithering::apply($im);
         }
 
         $width = imagesx($im);
@@ -138,49 +138,4 @@ public function setBlackThreshold(int $threshold): void
     {
         $this->blackThreshold = $threshold;
     }
-
-    protected function applyDithering(GdImage $im, int $threshold = 128): void
-    {
-        $w = imagesx($im);
-        $h = imagesy($im);
-
-        $gray = [];
-        for ($y = 0; $y < $h; $y++) {
-            $base = $y * $w;
-            for ($x = 0; $x < $w; $x++) {
-                $rgb = imagecolorat($im, $x, $y);
-                $r = ($rgb >> 16) & 0xFF;
-                $g = ($rgb >> 8) & 0xFF;
-                $b = $rgb & 0xFF;
-                $gray[$base + $x] = ($r * 299 + $g * 587 + $b * 114) / 1000;
-            }
-        }
-
-        $fs = [[1, 0, 7 / 16], [-1, 1, 3 / 16], [0, 1, 5 / 16], [1, 1, 1 / 16]];
-        for ($y = 0; $y < $h; $y++) {
-            $base = $y * $w;
-            for ($x = 0; $x < $w; $x++) {
-                $i = $base + $x;
-                $old = $gray[$i];
-                $gray[$i] = $new = $old < $threshold ? 0 : 255;
-                $error = $old - $new;
-                foreach ($fs as $m) {
-                    $nx = $x + $m[0];
-                    $ny = $y + $m[1];
-                    if ($nx >= 0 && $nx < $w && $ny < $h) {
-                        $ni = $ny * $w + $nx;
-                        $v = $gray[$ni] + $error * $m[2];
-                        $gray[$ni] = $v <= 0 ? 0 : (min($v, 255));
-                    }
-                }
-            }
-        }
-        for ($y = 0; $y < $h; $y++) {
-            $base = $y * $w;
-            for ($x = 0; $x < $w; $x++) {
-                $v = (int) $gray[$base + $x];
-                imagesetpixel($im, $x, $y, ($v << 16) | ($v << 8) | $v);
-            }
-        }
-    }
 }