Doxygen tutorials: basic structure

2014-11-27 15:39:05 +03:00
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+OpenCV iOS - Image Processing {#tutorial_image_manipulation}
+=============================
+
+Goal
+----
+
+In this tutorial we will learn how to do basic image processing using OpenCV in iOS.
+
+*Introduction*
+--------------
+
+In *OpenCV* all the image processing operations are usually carried out on the *Mat* structure. In
+iOS however, to render an image on screen it have to be an instance of the *UIImage* class. To
+convert an *OpenCV Mat* to an *UIImage* we use the *Core Graphics* framework available in iOS. Below
+is the code needed to covert back and forth between Mat's and UIImage's.
+@code{.cpp}
+- (cv::Mat)cvMatFromUIImage:(UIImage *)image
+{
+  CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage);
+  CGFloat cols = image.size.width;
+  CGFloat rows = image.size.height;
+
+  cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels (color channels + alpha)
+
+  CGContextRef contextRef = CGBitmapContextCreate(cvMat.data,                 // Pointer to  data
+                                                 cols,                       // Width of bitmap
+                                                 rows,                       // Height of bitmap
+                                                 8,                          // Bits per component
+                                                 cvMat.step[0],              // Bytes per row
+                                                 colorSpace,                 // Colorspace
+                                                 kCGImageAlphaNoneSkipLast |
+                                                 kCGBitmapByteOrderDefault); // Bitmap info flags
+
+  CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage);
+  CGContextRelease(contextRef);
+
+  return cvMat;
+}
+@endcode
+@code{.cpp}
+- (cv::Mat)cvMatGrayFromUIImage:(UIImage *)image
+{
+  CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage);
+  CGFloat cols = image.size.width;
+  CGFloat rows = image.size.height;
+
+  cv::Mat cvMat(rows, cols, CV_8UC1); // 8 bits per component, 1 channels
+
+  CGContextRef contextRef = CGBitmapContextCreate(cvMat.data,                 // Pointer to data
+                                                 cols,                       // Width of bitmap
+                                                 rows,                       // Height of bitmap
+                                                 8,                          // Bits per component
+                                                 cvMat.step[0],              // Bytes per row
+                                                 colorSpace,                 // Colorspace
+                                                 kCGImageAlphaNoneSkipLast |
+                                                 kCGBitmapByteOrderDefault); // Bitmap info flags
+
+  CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage);
+  CGContextRelease(contextRef);
+
+  return cvMat;
+ }
+@endcode
+After the processing we need to convert it back to UIImage. The code below can handle both
+gray-scale and color image conversions (determined by the number of channels in the *if* statement).
+@code{.cpp}
+cv::Mat greyMat;
+cv::cvtColor(inputMat, greyMat, COLOR_BGR2GRAY);
+@endcode
+After the processing we need to convert it back to UIImage.
+@code{.cpp}
+-(UIImage *)UIImageFromCVMat:(cv::Mat)cvMat
+{
+  NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize()*cvMat.total()];
+  CGColorSpaceRef colorSpace;
+
+  if (cvMat.elemSize() == 1) {
+      colorSpace = CGColorSpaceCreateDeviceGray();
+  } else {
+      colorSpace = CGColorSpaceCreateDeviceRGB();
+  }
+
+  CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
+
+  // Creating CGImage from cv::Mat
+  CGImageRef imageRef = CGImageCreate(cvMat.cols,                                 //width
+                                     cvMat.rows,                                 //height
+                                     8,                                          //bits per component
+                                     8 * cvMat.elemSize(),                       //bits per pixel
+                                     cvMat.step[0],                            //bytesPerRow
+                                     colorSpace,                                 //colorspace
+                                     kCGImageAlphaNone|kCGBitmapByteOrderDefault,// bitmap info
+                                     provider,                                   //CGDataProviderRef
+                                     NULL,                                       //decode
+                                     false,                                      //should interpolate
+                                     kCGRenderingIntentDefault                   //intent
+                                     );
+
+
+  // Getting UIImage from CGImage
+  UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
+  CGImageRelease(imageRef);
+  CGDataProviderRelease(provider);
+  CGColorSpaceRelease(colorSpace);
+
+  return finalImage;
+ }
+@endcode
+*Output*
+--------
+
+![image](images/output.jpg)
+
+Check out an instance of running code with more Image Effects on
+[YouTube](http://www.youtube.com/watch?v=Ko3K_xdhJ1I) .
+
+\htmlonly
+<div align="center">
+<iframe width="560" height="350" src="http://www.youtube.com/embed/Ko3K_xdhJ1I" frameborder="0" allowfullscreen></iframe>
+</div>
+\endhtmlonly
+