UIImage和IplImage之间的相互转换

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最新推荐文章于 2025-08-06 14:26:01 发布

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分类专栏： iPhone开发 OpenCV 文章标签： structure processing image iphone buffer object

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本文详细介绍了如何使用iPhone SDK中的UIImage对象在屏幕上显示图像，并通过OpenCV库中的IplImage结构进行图像处理。包括从UIImage到IplImage的转换方法，以及从IplImage到UIImage的转换步骤，确保了图像数据的有效传输和利用。

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Converting images between UIImage and IplImage

This content is copied from Yoshimasa's blog.

Converting images between UIImage and IplImage

OpenCV is using IplImage structure for processing, and iPhone SDK using UIImage object to display it on the screen. This means, we need a converter between UIImage and IplImage. Thankfully, we can do with iPhone SDK APIs.

Creating IplImage from UIImage is like this.

// NOTE you SHOULD cvReleaseImage() for the return value when end of the code.
- (IplImage *)CreateIplImageFromUIImage:(UIImage *)image {
  // Getting CGImage from UIImage
  CGImageRef imageRef = image.CGImage;

  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  // Creating temporal IplImage for drawing
  IplImage *iplimage = cvCreateImage(
    cvSize(image.size.width,image.size.height), IPL_DEPTH_8U, 4
  );
  // Creating CGContext for temporal IplImage
  CGContextRef contextRef = CGBitmapContextCreate(
    iplimage->imageData, iplimage->width, iplimage->height,
    iplimage->depth, iplimage->widthStep,
    colorSpace, kCGImageAlphaPremultipliedLast|kCGBitmapByteOrderDefault
  );
  // Drawing CGImage to CGContext
  CGContextDrawImage(
    contextRef,
    CGRectMake(0, 0, image.size.width, image.size.height),
    imageRef
  );
  CGContextRelease(contextRef);
  CGColorSpaceRelease(colorSpace);

  // Creating result IplImage
  IplImage *ret = cvCreateImage(cvGetSize(iplimage), IPL_DEPTH_8U, 3);
  cvCvtColor(iplimage, ret, CV_RGBA2BGR);
  cvReleaseImage(&iplimage);

  return ret;
}

Don’t forget release IplImage after using it by cvReleaseImage!

And creating UIImage from IplImage is like this.

// NOTE You should convert color mode as RGB before passing to this function
- (UIImage *)UIImageFromIplImage:(IplImage *)image {
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  // Allocating the buffer for CGImage
  NSData *data =
    [NSData dataWithBytes:image->imageData length:image->imageSize];
  CGDataProviderRef provider =
    CGDataProviderCreateWithCFData((CFDataRef)data);
  // Creating CGImage from chunk of IplImage
  CGImageRef imageRef = CGImageCreate(
    image->width, image->height,
    image->depth, image->depth * image->nChannels, image->widthStep,
    colorSpace, kCGImageAlphaNone|kCGBitmapByteOrderDefault,
    provider, NULL, false, kCGRenderingIntentDefault
  );
  // Getting UIImage from CGImage
  UIImage *ret = [UIImage imageWithCGImage:imageRef];
  CGImageRelease(imageRef);
  CGDataProviderRelease(provider);
  CGColorSpaceRelease(colorSpace);
  return ret;
}