how to convert from cvMat to UIImage in objective-c?

Question

I\'m using the OpenCV framework with XCode and want to convert from cvMat or IplImage to UIImage, how to do that? Thanks.

Answer 1

As a category:

#import 
#import 
using namespace cv;

@interface UIImage (OCV)

-(id)initWithOImage:(cv::Mat)oImage;
-(cv::Mat)oImage;

@end

and

#import "UIImage+OCV.h"

@implementation UIImage (OCV)

-(id)initWithOImage:(cv::Mat)oImage
{
  NSData *data = [NSData dataWithBytes:oImage.data length:oImage.elemSize() * oImage.total()];

  CGColorSpaceRef colorSpace;

  if (oImage.elemSize() == 1) {
    colorSpace = CGColorSpaceCreateDeviceGray();
  } else {
    colorSpace = CGColorSpaceCreateDeviceRGB();
  }

  CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);

  CGImageRef imageRef = CGImageCreate(oImage.cols,                                     // Width
                                      oImage.rows,                                     // Height
                                      8,                                              // Bits per component
                                      8 * oImage.elemSize(),                           // Bits per pixel
                                      oImage.step[0],                                  // Bytes per row
                                      colorSpace,                                     // Colorspace
                                      kCGImageAlphaNone | kCGBitmapByteOrderDefault,  // Bitmap info flags
                                      provider,                                       // CGDataProviderRef
                                      NULL,                                           // Decode
                                      false,                                          // Should interpolate
                                      kCGRenderingIntentDefault);                     // Intent

  self = [self initWithCGImage:imageRef];

  CGImageRelease(imageRef);
  CGDataProviderRelease(provider);
  CGColorSpaceRelease(colorSpace);

  return self;
}

-(cv::Mat)oImage
{
  CGColorSpaceRef colorSpace = CGImageGetColorSpace(self.CGImage);
  CGFloat cols = self.size.width;
  CGFloat rows = self.size.height;

  cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels

  CGContextRef contextRef = CGBitmapContextCreate(cvMat.data,                 // Pointer to backing 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), self.CGImage);
  CGContextRelease(contextRef);

  return cvMat;
}

@end