color replacement in image for iphone application - iphone

Question

Basically i want to implement color replacement feature for my paint application.
Below are original and expected output
Original:
After changing wall color selected by user along with some threshold for replacement
I have tried two approaches but could not got working as expected
Approach 1:
Queue-based Flood Fill algorithm for color replacement
but with i got below output with terribly slow and wall shadow has not been preserved.
Approach 2:
So i have tried to look at another option and found below post from SO
How to change a particular color in an image?
but i could not understand logic and not sure about my code implementation from step 3.
Please find below code for each step wise with my understanding.
1) Convert the image from RGB to HSV using cvCvtColor (we only want to
change the hue).
IplImage *mainImage=[self CreateIplImageFromUIImage:[UIImage imageNamed:#"original.jpg"]];
IplImage *hsvImage = cvCreateImage(cvGetSize(mainImage), IPL_DEPTH_8U, 3);
IplImage *threshImage = cvCreateImage(cvGetSize(mainImage), IPL_DEPTH_8U, 3);
cvCvtColor(mainImage,hsvImage,CV_RGB2HSV);
2) Isolate a color with cvThreshold specifying a
certain tolerance (you want a range of colors, not one flat color).
cvThreshold(hsvImage, threshImage, 0, 100, CV_THRESH_BINARY);
3) Discard areas of color below a minimum size using a blob detection
library like cvBlobsLib. This will get rid of dots of the similar
color in the scene. Do i need to specify original image or thresold image?
CBlobResult blobs = CBlobResult(threshImage, NULL, 0);
blobs.Filter( blobs, B_EXCLUDE, CBlobGetArea(), B_LESS, 10);
4) Mask the color with cvInRangeS and use the
resulting mask to apply the new hue.
Not sure about this function how it helps in color replacement and not able to understand arguments to be provided.
5) cvMerge the new image with the
new hue with an image composed by the saturation and brightness
channels that you saved in step one.
i understand that cvMerge will merge three channel of H S and V but how i can use output of above three steps.
so basically stuck with opencv implementation,
if possible then please guide me for opencv implemenation or any other solution to tryout.

Answer 1

Finally i am able to achieve some desired output using below javacv code and same ported to opencv too.
this solution has 2 problems
don't have edge detection, i think using contours i can achieve it
replaced color has flat hue and sat which should set based on source
pixel hue sat difference but not sure how to achieve that. may be
instead of cvSet using cvAddS
IplImage image = cvLoadImage("sample.png");
CvSize cvSize = cvGetSize(image);
IplImage hsvImage = cvCreateImage(cvSize, image.depth(),image.nChannels());
IplImage hChannel = cvCreateImage(cvSize, image.depth(), 1);
IplImage sChannel = cvCreateImage(cvSize, image.depth(), 1);
IplImage vChannel = cvCreateImage(cvSize, image.depth(), 1);
cvSplit(hsvImage, hChannel, sChannel, vChannel, null);
IplImage cvInRange = cvCreateImage(cvSize, image.depth(), 1);
CvScalar source=new CvScalar(72/2,0.07*255,66,0); //source color to replace
CvScalar from=getScaler(source,false);
CvScalar to=getScaler(source, true);
cvInRangeS(hsvImage, from , to, cvInRange);
IplImage dest = cvCreateImage(cvSize, image.depth(), image.nChannels());
IplImage temp = cvCreateImage(cvSize, IPL_DEPTH_8U, 2);
cvMerge(hChannel, sChannel, null, null, temp);
cvSet(temp, new CvScalar(45,255,0,0), cvInRange);// destination hue and sat
cvSplit(temp, hChannel, sChannel, null, null);
cvMerge(hChannel, sChannel, vChannel, null, dest);
cvCvtColor(dest, dest, CV_HSV2BGR);
cvSaveImage("output.png", dest);
method to for calculating threshold
CvScalar getScaler(CvScalar seed,boolean plus){
if(plus){
return CV_RGB(seed.red()+(seed.red()*thresold),seed.green()+(seed.green()*thresold),seed.blue()+(seed.blue()*thresold));
}else{
return CV_RGB(seed.red()-(seed.red()*thresold),seed.green()-(seed.green()*thresold),seed.blue()-(seed.blue()*thresold));
}
}

Answer 2

I know this answer will be useful to someone someday.
try this out in your view viewdidLoad() override method for iOS.
image in the code snippet below should be from your UIImageView
seed also is fixed.you can make it dynamic based on user tap event.
cv::Mat mask = cv::Mat::zeros(image.rows + 2, image.cols + 2, CV_8U);
imageView.image = [self UIImageFromCVMat:image];
cv::cvtColor(image, image, cv::COLOR_BGR2RGB);
try {
if(seed.x > 0 && seed.y > 0){
cv::floodFill(image, mask, seed, cv::Scalar(50, 155, 20) ,0, cv::Scalar(2,2, 2), cv::Scalar(2,2, 2), 8);
cv::floodFill(image, mask, seed2, cv::Scalar(50, 155, 20) ,0, cv::Scalar(2,2, 2), cv::Scalar(2,2, 2), 8);
cv::floodFill(image, mask, seed3, cv::Scalar(50, 155, 0) ,0, cv::Scalar(2,2, 2), cv::Scalar(2,2, 2), 8);
}
} catch (Exception ex) {
}
cv::cvtColor(image, image, cv::COLOR_RGB2BGR);
self.imageView.contentMode = UIViewContentModeScaleAspectFill;
self.imageView.image = [self UIImageFromCVMat:image];