improve antialiasing of polylines

Release v0.2.0

Antialiasing for route feature is not optional anymore.

Antialiasing is done by considering the whole polyline and calculating alpha values in a buffer before drawing single pixels.

Author: laufhannes

README.md

@@ -71,7 +71,7 @@ The MIT License (MIT). Please see [License File](LICENSE) for more information.
 [ico-downloads]: https://img.shields.io/packagist/dt/runalyze/static-maps.svg?style=flat-square
 
 [link-packagist]: https://packagist.org/packages/runalyze/static-maps
-[link-travis]: https://travis-ci.org/runalyze/static-maps
+[link-travis]: https://travis-ci.org/Runalyze/static-maps
 [link-scrutinizer]: https://scrutinizer-ci.com/g/runalyze/static-maps/code-structure
 [link-code-quality]: https://scrutinizer-ci.com/g/runalyze/static-maps
 [link-downloads]: https://packagist.org/packages/runalyze/static-maps

docs/examples/example-3.png

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the StaticMaps.
+ *
+ * (c) RUNALYZE <[email protected]>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+namespace Runalyze\StaticMaps\Drawer;
+
+interface PainterAwareInterface
+{
+    /**
+     * Set painter for drawing
+     *
+     * Set color specification in rgb-code as well as opacity and line width for later drawing.
+     *
+     * @param int $r         [0 .. 255]
+     * @param int $g         [0 .. 255]
+     * @param int $b         [0 .. 255]
+     * @param float $alpha   (0.0 .. 100.0]
+     * @param int $lineWidth [px]
+     */
+    public function setPainter(int $r, int $g, int $b, float $alpha = 100.0, int $lineWidth = 1);
+}

src/Drawer/AntialiasDrawer.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the StaticMaps.
+ *
+ * (c) RUNALYZE <[email protected]>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+namespace Runalyze\StaticMaps\Drawer;
+
+trait PainterAwareTrait
+{
+    /** @var int[] [r, g, b] */
+    protected $PainterColor = [0, 0, 0];
+
+    /** @var float (0.0 .. 100.0) */
+    protected $PainterAlpha = 100.0;
+
+    /** @var int [px] */
+    protected $LineWidth = 1;
+
+    public function setPainter(int $r, int $g, int $b, float $alpha = 100.0, int $lineWidth = 1)
+    {
+        $this->PainterColor = [$r, $g, $b];
+        $this->PainterAlpha = $alpha;
+        $this->LineWidth = $lineWidth;
+    }
+
+    protected function allocateColor($resource, float $alpha = null): int
+    {
+        $alpha = null !== $alpha ? $alpha : $this->PainterAlpha;
+
+        return imagecolorallocatealpha($resource, $this->PainterColor[0], $this->PainterColor[1], $this->PainterColor[2], (int)(127.0 - $alpha * 127.0 / 100.0));
+    }
+}

src/Drawer/PainterAwareInterface.php

@@ -0,0 +1,151 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the StaticMaps.
+ *
+ * (c) RUNALYZE <[email protected]>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+namespace Runalyze\StaticMaps\Drawer\Polyline;
+
+use Runalyze\StaticMaps\Drawer\PainterAwareTrait;
+
+class AntialiasPolylineDrawer implements PolylineDrawerInterface
+{
+    use PainterAwareTrait;
+
+    /** @var array [x][y] => alpha */
+    protected $AlphaPixels = [];
+
+    public function addPolyline(array $points)
+    {
+        $numPoints = count($points);
+
+        if (1 == $numPoints) {
+            $this->drawAntialiasPixelToBuffer($points[0][0], $points[0][1]);
+
+            return;
+        }
+
+        $previousAngle = $this->getAngle($points[0][0], $points[0][1], $points[1][0], $points[1][1]);
+        $currentAngle = $previousAngle;
+
+        for ($i = 0; $i < $numPoints - 1; ++$i) {
+            $nextAngle = $i < $numPoints - 2 ? $this->getAngle($points[$i + 1][0], $points[$i + 1][1], $points[$i + 2][0], $points[$i + 2][1]) : $currentAngle;
+
+            list($Ax, $Ay) = $points[$i];
+            list($Bx, $By) = $points[$i + 1];
+
+            $transitionAngleAtA = ($currentAngle + $previousAngle) / 2.0 - 90.0;
+            $transitionAngleAtB = ($currentAngle + $nextAngle) / 2.0 - 90.0;
+            $weightFactorAtA = 1.0 / cos(deg2rad(($previousAngle - $currentAngle) / 2.0));
+            $weightFactorAtB = 1.0 / cos(deg2rad(($currentAngle - $nextAngle) / 2.0));
+
+            $weights = range(0.5 - $this->LineWidth / 2, $this->LineWidth / 2 - 0.5, 1.0);
+
+            foreach ($weights as $weight) {
+                $this->drawAntialiasLineToBuffer(
+                    $Ax + $weight * $weightFactorAtA * cos(deg2rad($transitionAngleAtA)),
+                    $Ay + $weight * $weightFactorAtA * sin(deg2rad($transitionAngleAtA)),
+                    $Bx + $weight * $weightFactorAtB * cos(deg2rad($transitionAngleAtB)),
+                    $By + $weight * $weightFactorAtB * sin(deg2rad($transitionAngleAtB)),
+                    1
+                );
+            }
+
+            $previousAngle = $currentAngle;
+            $currentAngle = $nextAngle;
+        }
+    }
+
+    public function drawPolylines($resource)
+    {
+        foreach ($this->AlphaPixels as $x => $yPixels) {
+            foreach ($yPixels as $y => $alpha) {
+                imagesetpixel($resource, $x, $y, $this->allocateColor($resource, $alpha));
+            }
+        }
+
+        $this->AlphaPixels = [];
+    }
+
+    protected function drawAntialiasLineToBuffer($x1, $y1, $x2, $y2, int $lineWidth = 1)
+    {
+        if (1 == $lineWidth) {
+            $this->drawAntialiasLinePixelwiseToBuffer($x1, $y1, $x2, $y2);
+
+            return;
+        }
+
+        $angle = deg2rad($this->getAngle($x1, $y1, $x2, $y2) - 90.0);
+        $weights = range(0.5 - $lineWidth / 2, $lineWidth / 2 - 0.5, 1.0);
+
+        foreach ($weights as $weight) {
+            $this->drawAntialiasLineToBuffer(
+                $x1 + $weight * cos($angle),
+                $y1 + $weight * sin($angle),
+                $x2 + $weight * cos($angle),
+                $y2 + $weight * sin($angle)
+            );
+        }
+    }
+
+    protected function drawAntialiasLinePixelwiseToBuffer($x1, $y1, $x2, $y2)
+    {
+        $distance = max(1.0, sqrt(($x2 - $x1) * ($x2 - $x1) + ($y2 - $y1) * ($y2 - $y1)));
+
+        $xStep = ($x2 - $x1) / $distance;
+        $yStep = ($y2 - $y1) / $distance;
+
+        for ($i = 0; $i <= $distance; ++$i) {
+            $this->drawAntialiasPixelToBuffer($i * $xStep + $x1, $i * $yStep + $y1);
+        }
+    }
+
+    protected function drawAntialiasPixelToBuffer(float $x, float $y)
+    {
+        $xi = (int)floor($x);
+        $yi = (int)floor($y);
+        
+        if ($xi == $x && $yi == $y) {
+            $this->drawAlphaPixelToBuffer($xi, $yi, $this->PainterAlpha);
+        } else {
+            $deltaX = $x - (float)$xi;
+            $deltaY = $y - (float)$yi;
+            $alpha1 = (1.0 - $deltaX) * (1.0 - $deltaY) * $this->PainterAlpha;
+            $alpha2 = $deltaX * (1.0 - $deltaY) * $this->PainterAlpha;
+            $alpha3 = (1.0 - $deltaX) * $deltaY * $this->PainterAlpha;
+            $alpha4 = $deltaX * $deltaY * $this->PainterAlpha;
+
+            $this->drawAlphaPixelToBuffer($xi, $yi, $alpha1);
+            $this->drawAlphaPixelToBuffer($xi + 1, $yi, $alpha2);
+            $this->drawAlphaPixelToBuffer($xi, $yi + 1, $alpha3);
+            $this->drawAlphaPixelToBuffer($xi + 1, $yi + 1, $alpha4);
+        }
+    }
+
+    protected function drawAlphaPixelToBuffer(int $x, int $y, float $alpha)
+    {
+        if (isset($this->AlphaPixels[$x][$y])) {
+            $this->AlphaPixels[$x][$y] = min($this->PainterAlpha, $this->AlphaPixels[$x][$y] + $alpha);
+        } else {
+            $this->AlphaPixels[$x][$y] = $alpha;
+        }
+    }
+
+    protected function getAngle($x1, $y1, $x2, $y2): float
+    {
+        $angle = rad2deg(atan2($y2 - $y1, $x2 - $x1));
+
+        if ($angle <= 0.0) {
+            return 360.0 - abs($angle);
+        }
+
+        return $angle;
+    }
+}