Converting to UIImage from cvMat alters image - c++

Question

Whenever I try to convert my binary image back to a UIImage it changes the areas that should be white to a dark blue. I have seen that other people have been having similar issues, but have found no solution.
Here is the code I am using to convert to a UIImage
- (UIImage *)UIImageFromMat:(cv::Mat)image
{
NSData *data = [NSData dataWithBytes:image.data length:image.elemSize()*image.total()];
CGColorSpaceRef colorSpace;
if (image.elemSize() == 1) {
colorSpace = CGColorSpaceCreateDeviceGray();
} else {
colorSpace = CGColorSpaceCreateDeviceRGB();
}
CGDataProviderRef provider = CGDataProviderCreateWithCFData((CFDataRef)data);//CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
// Creating CGImage from cv::Mat
CGImageRef imageRef = CGImageCreate(image.cols, //width
image.rows, //height
8, //bits per component
8 * image.elemSize(), //bits per pixel
image.step.p[0], //bytesPerRow
colorSpace, //colorspace
kCGImageAlphaNone|kCGBitmapByteOrderDefault,// bitmap info
provider, //CGDataProviderRef
NULL, //decode
false, //should interpolate
kCGRenderingIntentDefault //intent
);
// Getting UIImage from CGImage
UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
//[self.imgView setImage:finalImage];
CGImageRelease(imageRef);
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpace);
return finalImage;
}
Can anyone provide some insight as to why my code for converting to a UIImage changes the image? And how to fix it?

Answer 1

Found that I need to apply this code before converting to a UIImage
res.convertTo(res, CV_8UC3, 255.0);

Answer 2

I do not know what is the reason but you can fix an image using
CGImageRef CGImageCreateWithMaskingColors (
CGImageRef image,
const CGFloat components[]
);
Description Creates a bitmap image by masking an existing bitmap
image with the provided color values. Any image sample with color
value {c[1], ... c[N]} where min[i] <= c[i] <= max[i] for 1 <= i <= N
is masked out (that is, not painted). This means that anything
underneath the unpainted samples, such as the current fill color,
shows through.
So you will need something like
UIImage *your_image; // do not forget to initialize it
const CGFloat blueMasking[6] = {0.0, 0.05, 0.0, 0.05, 0.95, 1.0};
CGImageRef image = CGImageCreateWithMaskingColors(your_image.CGImage, blueMasking);
UIImage *new_image = [UIImage imageWithCGImage:image];
https://stackoverflow.com/questions/22429538/turn-all-pixels-of-chosen-color-to-white-uiimage/22429897#22429897