从Image中删除背景并仅拍摄图像部分以便在iOS中保存

2 回答

• 7

  通常，根据经验，背景颜色与所有其他颜色的差异越大，将图像分割为前景和背景就越容易 . 在这种情况下，正如@Chris已经建议的那样，可以使用简单的色度键实现 . 下面是我在Wikipedia上描述的键控的快速实现（它用C编写，但将其转换为Objective-C应该很简单）：

  /**
   * @brief Separate foreground from background using simple chroma keying.
   *
   * @param imageBGR   Image with monochrome background
   * @param chromaBGR  Color of the background (using channel order BGR and range [0, 255])
   * @param tInner     Inner threshold, color distances below this value will be counted as foreground
   * @param tOuter     Outer threshold, color distances above this value will be counted as background
   *
   * @return  Mask (0 - background, 255 - foreground, [1, 255] - partially fore- and background)
   *
   * Details can be found on [Wikipedia][1].
   *
   * [1]: https://en.wikipedia.org/wiki/Chroma_key#Programming
   */
  cv::Mat1b chromaKey( const cv::Mat3b & imageBGR, cv::Scalar chromaBGR, double tInner, double tOuter )
  {
      // Basic outline:
      //
      // 1. Convert the image to YCrCb.
      // 2. Measure Euclidean distances of color in YCrBr to chroma value.
      // 3. Categorize pixels:
      //   * color distances below inner threshold count as foreground; mask value = 0
      //   * color distances above outer threshold count as background; mask value = 255
      //   * color distances between inner and outer threshold a linearly interpolated; mask value = [0, 255]
  
      assert( tInner <= tOuter );
  
      // Convert to YCrCb.
      assert( ! imageBGR.empty() );
      cv::Size imageSize = imageBGR.size();
      cv::Mat3b imageYCrCb;
      cv::cvtColor( imageBGR, imageYCrCb, cv::COLOR_BGR2YCrCb );
      cv::Scalar chromaYCrCb = bgr2ycrcb( chromaBGR ); // Convert a single BGR value to YCrCb.
  
      // Build the mask.
      cv::Mat1b mask = cv::Mat1b::zeros( imageSize );
      const cv::Vec3d key( chromaYCrCb[ 0 ], chromaYCrCb[ 1 ], chromaYCrCb[ 2 ] );
  
      for ( int y = 0; y < imageSize.height; ++y )
      {
          for ( int x = 0; x < imageSize.width; ++x )
          {
              const cv::Vec3d color( imageYCrCb( y, x )[ 0 ], imageYCrCb( y, x )[ 1 ], imageYCrCb( y, x )[ 2 ] );
              double distance = cv::norm( key - color );
  
              if ( distance < tInner )
              {
                  // Current pixel is fully part of the background.
                  mask( y, x ) = 0;
              }
              else if ( distance > tOuter )
              {
                  // Current pixel is fully part of the foreground.
                  mask( y, x ) = 255;
              }
              else
              {
                  // Current pixel is partially part both, fore- and background; interpolate linearly.
                  // Compute the interpolation factor and clip its value to the range [0, 255].
                  double d1 = distance - tInner;
                  double d2 = tOuter   - tInner;
                  uint8_t alpha = static_cast< uint8_t >( 255. * ( d1 / d2 ) );
  
                  mask( y, x ) = alpha;
              }
          }
      }
  
      return mask;
  }
  

  可以在Github Gist中找到完整的代码示例 .

  不幸的是，你的例子不遵循这个经验法则 . 由于前景和背景的强度不同，因此很难（甚至不可能）找到一组全局参数以实现良好的分离：

  • 对象周围有黑线但对象内没有孔（ tInner=50 ， tOuter=90 ）
    

  

  • 对象周围没有黑线，但对象内部没有空洞（ tInner=100 ，_ tOuter=170 ）
    

  

  因此，如果您无法更改图像的背景，则需要采用更复杂的方法 . 但是，快速简单的示例实现有点超出范围，但您可能希望查看image segmentation和alpha matting的相关区域 .

  回复于 2024-05-03T07:56:42+08:00
• 4

  我认为你需要使用一个抠像 - 虽然你选择黑色我认为它应该工作 .

  一个快速谷歌想出了this

  回复于 2024-05-03T07:56:42+08:00