Add conversion methods to ResolutionInterface

src/Interfaces/ResolutionInterface.php

@@ -4,6 +4,68 @@ namespace Intervention\Image\Interfaces;
 
 interface ResolutionInterface
 {
+    /**
+     * Return resolution of x-axis
+     *
+     * @return float
+     */
     public function x(): float;
+
+    /**
+     * Set resolution on x-axix
+     *
+     * @param  float $x
+     * @return ResolutionInterface
+     */
+    public function setX(float $x): ResolutionInterface;
+
+    /**
+     * Return resolution on y-axis
+     *
+     * @return float
+     */
     public function y(): float;
+
+    /**
+     * Set resolution on y-axis
+     *
+     * @param  float $y
+     * @return ResolutionInterface
+     */
+    public function setY(float $y): ResolutionInterface;
+
+    /**
+     * Convert the resolution to DPI
+     *
+     * @return ResolutionInterface
+     */
+    public function perInch(): ResolutionInterface;
+
+    /**
+     * Convert the resolution to DPCM
+     *
+     * @return ResolutionInterface
+     */
+    public function perCm(): ResolutionInterface;
+
+    /**
+     * Return string representation of unit
+     *
+     * @return string
+     */
+    public function unit(): string;
+
+    /**
+     * Transform object to string
+     *
+     * @return string
+     */
+    public function toString(): string;
+
+    /**
+     * Cast object to string
+     *
+     * @return string
+     */
+    public function __toString(): string;
 }

src/Resolution.php

@@ -6,18 +6,142 @@ use Intervention\Image\Interfaces\ResolutionInterface;
 
 class Resolution implements ResolutionInterface
 {
-    public function __construct(protected float $x, protected float $y)
+    public const PER_INCH = 1;
-    {
+    public const PER_CM = 2;
+
+    /**
+     * Create new instance
+     *
+     * @param float $x
+     * @param float $y
+     * @param int $per_unit
+     */
+    public function __construct(
+        protected float $x,
+        protected float $y,
+        protected int $per_unit = self::PER_INCH
+    ) {
         //
     }
 
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::x()
+     */
     public function x(): float
     {
         return $this->x;
     }
 
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::setX()
+     */
+    public function setX(float $x): self
+    {
+        $this->x = $x;
+
+        return $this;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::y()
+     */
     public function y(): float
     {
         return $this->y;
     }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::setY()
+     */
+    public function setY(float $y): self
+    {
+        $this->y = $y;
+
+        return $this;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::setPerUnit()
+     */
+    protected function setPerUnit(int $per_unit): self
+    {
+        $this->per_unit = $per_unit;
+
+        return $this;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::unit()
+     */
+    public function unit(): string
+    {
+        return match ($this->per_unit) {
+            self::PER_CM => 'dpcm',
+            default => 'dpi',
+        };
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::perInch()
+     */
+    public function perInch(): self
+    {
+        return match ($this->per_unit) {
+            self::PER_CM => $this
+                ->setPerUnit(self::PER_INCH)
+                ->setX($this->x * (1 / 2.54))
+                ->setY($this->y * (1 / 2.54)),
+            default => $this
+        };
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::perCm()
+     */
+    public function perCm(): self
+    {
+        return match ($this->per_unit) {
+            self::PER_INCH => $this
+                ->setPerUnit(self::PER_CM)
+                ->setX($this->x / (1 / 2.54))
+                ->setY($this->y / (1 / 2.54)),
+            default => $this,
+        };
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::toString()
+     */
+    public function toString(): string
+    {
+        return sprintf("%1\$.2f x %2\$.2f %3\$s", $this->x, $this->y, $this->unit());
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ResolutionInterface::__toString()
+     */
+    public function __toString(): string
+    {
+        return $this->toString();
+    }
 }

tests/ResolutionTest.php

@@ -21,4 +21,36 @@ class ResolutionTest extends TestCase
         $this->assertEquals(1.2, $resolution->x());
         $this->assertEquals(3.4, $resolution->y());
     }
+
+    public function testPerInch(): void
+    {
+        $resolution = new Resolution(300, 150); // per inch
+        $this->assertEquals(300, $resolution->perInch()->x());
+        $this->assertEquals(150, $resolution->perInch()->y());
+
+        $resolution = new Resolution(300, 150, Resolution::PER_CM);
+        $this->assertEquals(118.11024, round($resolution->perInch()->x(), 5));
+        $this->assertEquals(59.05512, round($resolution->perInch()->y(), 5));
+    }
+
+    public function testPerCm(): void
+    {
+        $resolution = new Resolution(118.11024, 59.05512); // per inch
+        $this->assertEquals(300, round($resolution->perCm()->x()));
+        $this->assertEquals(150, round($resolution->perCm()->y()));
+
+        $resolution = new Resolution(300, 150, Resolution::PER_CM);
+        $this->assertEquals(300, $resolution->perCm()->x());
+        $this->assertEquals(150, $resolution->perCm()->y());
+    }
+
+    public function testToString(): void
+    {
+        $resolution = new Resolution(300, 150, Resolution::PER_CM);
+        $this->assertEquals('300.00 x 150.00 dpcm', $resolution->toString());
+
+        $resolution = new Resolution(300, 150, Resolution::PER_INCH);
+        $this->assertEquals('300.00 x 150.00 dpi', $resolution->toString());
+        $this->assertEquals('300.00 x 150.00 dpi', (string) $resolution);
+    }
 }