问题
I have a png image with green and red lines and transparent background, which I need to use is as a mask for executing GrabCut. But I get unexpected results. Here's my code:
//find the mask
Mat mask;
mask.create( image.size(), CV_8UC1);
mask.setTo(Scalar::all(GC_BGD));
Mat maskImg = imread("messi5.png");
for(int i=0; i<maskImg.cols; i++)
for(int j=0; j<maskImg.rows; j++)
{
//if it's red, make it white
if ((int)maskImg.at<cv::Vec3b>(j,i)[0]==0 && (int)maskImg.at<cv::Vec3b>(j,i)[1] == 0 && (int)maskImg.at<cv::Vec3b>(j,i)[2] == 255) {
mask.at<cv::Vec3b>(j,i)[0]= GC_BGD;
mask.at<cv::Vec3b>(j,i)[1] = GC_BGD;
mask.at<cv::Vec3b>(j,i)[2] = GC_BGD;
}
//if it's green, make it black
if ((int)maskImg.at<cv::Vec3b>(j,i)[0]==0 && (int)maskImg.at<cv::Vec3b>(j,i)[1] == 255 && (int)maskImg.at<cv::Vec3b>(j,i)[2] == 0) {
mask.at<cv::Vec3b>(j,i)[0] = GC_FGD;
mask.at<cv::Vec3b>(j,i)[1] = GC_FGD;
mask.at<cv::Vec3b>(j,i)[2] = GC_FGD;
}
}
...
Here's the output: http://prntscr.com/40kt4e. I guess it's like there's no rectangle, it only sees the GC_FGD pixels, everything else is considered BG. And it looks somehow scaled, but I have no idea how to fix it.
回答1:
i was trying to say in
GrabCut reading mask from PNG file in OpenCV (C++)
that your using the 3 channel accessor for a 1 channel image. this will mess things up a little, use the 1 channel version for the 1 channel mask:
Mat image;
image= cv::imread(file);
//everything outside this box will be set to def.
//background GC_BGD, clearly from the image you can see that the players legs are outside the box,
//so this will cause problems. you need to either change the box,
//such that everything is outside the box is the background, or use your mask to scribble on the players legs in green.
cv::Rect rectangle(startX, startY, width, height);
cv::Mat bgModel,fgModel;
//find the mask
Mat mask;
mask.create( image.size(), CV_8UC1); //CV_8UC1 is single channel
mask.setTo(Scalar::all(GC_BGD)); //you have set it to all def. background
Mat maskImg = imread("messi5.png");
for(int i=0; i<maskImg.cols; i++)
for(int j=0; j<maskImg.rows; j++)
{
//if it's red, make it black
if ((int)maskImg.at<cv::Vec3b>(j,i)[0]==0 && (int)maskImg.at<cv::Vec3b>(j,i)[1] == 0 && (int)maskImg.at<cv::Vec3b>(j,i)[2] == 255) {
//the whole mask is black so this is redundant
mask.at<uchar>(j,i)= GC_BGD; //GC_BGD := 0 := black
}
//if it's green, make it white
if ((int)maskImg.at<cv::Vec3b>(j,i)[0]==0 && (int)maskImg.at<cv::Vec3b>(j,i)[1] == 255 && (int)maskImg.at<cv::Vec3b>(j,i)[2] == 0) {
mask.at<uchar>(j,i) = GC_FGD; //GC_FGD:= 1 := white
}
}
For more efficient code for looping over images please see: http://docs.opencv.org/doc/tutorials/core/how_to_scan_images/how_to_scan_images.html
The LUT function my do the trick here: http://docs.opencv.org/doc/tutorials/core/how_to_scan_images/how_to_scan_images.html#the-core-function
来源:https://stackoverflow.com/questions/24631988/using-a-png-image-as-mask-for-grabcut