Can save an image from Mat to disk

Signed-off-by: deadprogram <ron@hybridgroup.com>

README.md

@@ -61,7 +61,7 @@ func main() {
 
 ### Ubuntu/Linux
 
-You can use `make` to install OpenCV 3.3 with the handy `Makefile` included with this repo. If you already have installed it, you do not need to do so again. Also the installation performed by the `Makefile` may remove options that you have already installed.
+You can use `make` to install OpenCV 3.3 with the handy `Makefile` included with this repo. If you already have installed it, you do not need to do so again. The installation performed by the `Makefile` is minimal, so it may remove OpenCV options if you have already installed it some other way.
 
 #### Install required packages
 

examples/saveimage.go

@@ -0,0 +1,42 @@
+// +build example
+//
+// Do not build by default.
+//
+// This example uses the VideoCapture class to capture a frame from a connected webcam,
+// then save it to a file on disk
+//
+// how to run:
+// 		go run ./examples/saveimage.go filename.jpg
+//
+package main
+
+import (
+	"fmt"
+	"os"
+
+	opencv3 ".."
+)
+
+func main() {
+	deviceID := 0
+	webcam := opencv3.NewVideoCapture()
+	defer webcam.Delete()
+
+	if ok := webcam.OpenDevice(int(deviceID)); !ok {
+		fmt.Printf("error opening device: %v\n", deviceID)
+	}
+
+	img := opencv3.NewMat()
+	defer img.Delete()
+
+	if ok := webcam.Read(img); !ok {
+		fmt.Printf("cannot read device %d\n", deviceID)
+		return
+	}
+	if img.Empty() {
+		fmt.Printf("no image on device %d\n", deviceID)
+		return
+	}
+
+	opencv3.IMWrite(os.Args[1], img)
+}

imgcodecs.cpp

@@ -5,3 +5,8 @@ Mat Image_IMRead(const char* filename, int flags) {
     cv::Mat img = cv::imread(filename, flags);
     return new cv::Mat(img);
 }
+
+bool Image_IMWrite(const char* filename, Mat img) {
+    return cv::imwrite(filename, *img);
+}
+

imgcodecs.go

@@ -16,3 +16,11 @@ func IMRead(name string, flags int) Mat {
 
 	return Mat{p: C.Image_IMRead(cName, C.int(flags))}
 }
+
+// IMWrite writes a Mat to an image file
+func IMWrite(name string, img Mat) bool {
+	cName := C.CString(name)
+	defer C.free(unsafe.Pointer(cName))
+
+	return bool(C.Image_IMWrite(cName, img.p))
+}

imgcodecs.h

@@ -1,6 +1,8 @@
 #ifndef _OPENCV3_IMGCODECS_H_
 #define _OPENCV3_IMGCODECS_H_
 
+#include <stdbool.h>
+
 #ifdef __cplusplus
 #include <opencv2/opencv.hpp>
 extern "C" {
@@ -9,6 +11,7 @@ extern "C" {
 #include "core.h"
 
 Mat Image_IMRead(const char* filename, int flags);
+bool Image_IMWrite(const char* filename, Mat img);
 
 #ifdef __cplusplus
 }