从图像中删除背景并仅保留图像部分以保存在 iOS

Question

这是我需要达到的目标：

从相机或画廊拍摄图像
从图像中删除背景并保存
背景应该是黑色或白色
还需要连同背景一起去除阴影

结果示例：

原图

结果图片

这是我试过的：

CGFloat colorMasking[6]={222,255,222,255,222,255};
CGImageRef imageRef = CGImageCreateWithMaskingColors([IMG CGImage], colorMasking);
UIImage  *resultThumbImage = [UIImage imageWithCGImage:imageRef scale:ThumbImage.scale orientation:IMG.imageOrientation];

它只适用于白色背景。它不是更有效。我需要获得我在上面图片中放置的准确结果。

我也参考了一些资料：

iOS how to mask the image background color

How to remove the background of image in iphone app?

Changing the background color of a captured image from camera to white

有人可以帮我实现这个吗？

任何参考或将不胜感激。

提前致谢。

Answer 1

我认为您需要使用色度键 - 虽然您选择的是黑色，但我认为它应该有效。

很快 google 想出了 this

Answer 2

一般来说，根据经验，背景颜色与所有其他颜色的差异越大，将图像分成前景和背景越容易。在这种情况下，@Chris 已经建议，可以使用简单的色度键实现。下面是我的快 Wikipedia 中描述的键控实现（它是用 C++ 编写的，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;
}

在此 Github Gist.

中可以找到完整的代码示例

不幸的是，您的示例没有遵循该经验法则。由于前景和背景仅在强度上有所不同很难（甚至不可能）找到一个单一的全球集良好分离的参数：

物体周围有黑线但物体内部没有孔(tInner=50,tOuter=90)
物体周围没有黑线但物体内部有孔(tInner=100,tOuter=170)

所以，如果您无法更进一步地更改图片的背景需要复杂的方法。但是，快速简单的示例实现有点超出范围，但您可能需要查看 image segmentation 和 alpha matting.

从图像中删除背景并仅保留图像部分以保存在 iOS

Remove background from Image & take only Image part for save in iOS

ios

opencv

uiimage

core-image

chromakey