Add resize and mirror flip

Author: vdechenaux

README.md

@@ -24,8 +24,12 @@ composer require vdechenaux/webcam
 
 ```php
 $webcam = new \VDX\Webcam\Webcam();
+
+// It can produce an other size if your webcam does not support the provided size
+$webcam->setDesiredSize(1280, 720);
+
 if ($webcam->open()) {
-    $webcam->saveFrame('/tmp/test.jpg');
+    $webcam->saveFrame('/tmp/test.jpg'/*, true*/); // It accepts a second parameter to mirror the image
     $webcam->close();
 }
 ```

src/Webcam.php

@@ -6,19 +6,31 @@ class Webcam
 {
     private \FFI $ffi;
     private ?\FFI\CData $cvCamera = null;
+    private ?int $desiredWidth = null;
+    private ?int $desiredHeight = null;
 
     /**
      * @throws \FFI\Exception If OpenCV is not available
      */
     public function __construct()
     {
         $def = <<<DEF
+            enum {
+                CV_CAP_ANY = 0
+            };
+            enum {
+                 CV_CAP_PROP_FRAME_WIDTH = 3,
+                 CV_CAP_PROP_FRAME_HEIGHT = 4
+            };
+        
             typedef struct CvCapture CvCapture;
             typedef struct IplImage IplImage;
             CvCapture* cvCreateCameraCapture(int index);
             IplImage* cvQueryFrame(CvCapture* capture);
             int cvSaveImage(const char *filename, const IplImage *image);
             void cvReleaseCapture (CvCapture **capture);
+            int cvSetCaptureProperty(CvCapture* capture, int property_id, double value);
+            void cvFlip(const IplImage* src, IplImage* dst, int flip_mode);
 DEF;
 
         $this->ffi = \FFI::cdef($def, "libopencv_videoio.so");
@@ -29,15 +41,35 @@ public function __destruct()
         $this->close();
     }
 
+    public function setDesiredSize(int $desiredWidth, int $desiredHeight): void
+    {
+        $this->desiredWidth = $desiredWidth;
+        $this->desiredHeight = $desiredHeight;
+
+        if ($this->cvCamera !== null) {
+            $this->ffi->cvSetCaptureProperty($this->cvCamera, $this->ffi->CV_CAP_PROP_FRAME_WIDTH, $this->desiredWidth);
+            $this->ffi->cvSetCaptureProperty($this->cvCamera, $this->ffi->CV_CAP_PROP_FRAME_HEIGHT, $this->desiredHeight);
+        }
+    }
+
     public function open(): bool
     {
         if ($this->cvCamera !== null) {
             return false;
         }
 
-        $this->cvCamera = $this->ffi->cvCreateCameraCapture(0);
+        $this->cvCamera = $this->ffi->cvCreateCameraCapture($this->ffi->CV_CAP_ANY);
+
+        if ($this->cvCamera === null) {
+            return false;
+        }
+
+        if ($this->desiredWidth !== null && $this->desiredHeight !== null) {
+            $this->ffi->cvSetCaptureProperty($this->cvCamera, $this->ffi->CV_CAP_PROP_FRAME_WIDTH, $this->desiredWidth);
+            $this->ffi->cvSetCaptureProperty($this->cvCamera, $this->ffi->CV_CAP_PROP_FRAME_HEIGHT, $this->desiredHeight);
+        }
 
-        return $this->cvCamera !== null;
+        return true;
     }
 
     public function close(): void
@@ -50,12 +82,22 @@ public function close(): void
         $this->cvCamera = null;
     }
 
-    public function saveFrame(string $filename): bool
+    public function saveFrame(string $filename, bool $mirror = false): bool
     {
         if ($this->cvCamera === null) {
             return false;
         }
 
-        return (bool) $this->ffi->cvSaveImage($filename, $this->ffi->cvQueryFrame($this->cvCamera));
+        $image = $this->ffi->cvQueryFrame($this->cvCamera);
+
+        if ($image === null) {
+            return false;
+        }
+
+        if ($mirror) {
+            $this->ffi->cvFlip($image, null, 1);
+        }
+
+        return (bool) $this->ffi->cvSaveImage($filename, $image);
     }
 }