I have a c++ opencv function that gets the gray scale of an image and stores it into an array.
+(cv::Mat) makeGray:(UIImage *) image {
// Transform UIImage to cv::Mat
cv::Mat imageMat;
UIImageToMat(image, imageMat);
//Transform image to grayscale
cv::Mat grayMat;
cv::cvtColor(imageMat, grayMat, CV_BGR2GRAY);
return grayMat;
}
Whenever I try storing this in a variable using swift
swift function:
#IBAction func convertImage(_ sender: UIButton) {
let grayMat = OpenCVWrapper.makeGray(photoImageView.image)
}
The entire program just freezes without throwing out an error.
The swift function works great when I return an UIImage:
+(UIImage *) makeGray:(UIImage *) image {
// Transform UIImage to cv::Mat
cv::Mat imageMat;
UIImageToMat(image, imageMat);
//Transform image to grayscale
cv::Mat grayMat;
cv::cvtColor(imageMat, grayMat, CV_BGR2GRAY);
return MatToUIImage(grayMat);
}
But I'm looking to return a 3darray and not an Image.
I am trying to apply adaptive thresholding to an image of an A4 paper as shown below:
I use the code below to apply the image manipulation:
+ (UIImage *)processImageWithOpenCV:(UIImage*)inputImage {
cv::Mat cvImage = [inputImage CVMat];
cv::Mat res;
cv::cvtColor(cvImage, cvImage, CV_RGB2GRAY);
cvImage.convertTo(cvImage,CV_32FC1,1.0/255.0);
CalcBlockMeanVariance(cvImage,res);
res=1.0-res;
res=cvImage+res;
cv::threshold(res,res, 0.85, 1, cv::THRESH_BINARY);
cv::resize(res, res, cv::Size(res.cols/2,res.rows/2));
return [UIImage imageWithCVMat:cvImage];
}
void CalcBlockMeanVariance(cv::Mat Img,cv::Mat Res,float blockSide=13) // blockSide - the parameter (set greater for larger font on image)
{
cv::Mat I;
Img.convertTo(I,CV_32FC1);
Res=cv::Mat::zeros(Img.rows/blockSide,Img.cols/blockSide,CV_32FC1);
cv::Mat inpaintmask;
cv::Mat patch;
cv::Mat smallImg;
cv::Scalar m,s;
for(int i=0;i<Img.rows-blockSide;i+=blockSide)
{
for (int j=0;j<Img.cols-blockSide;j+=blockSide)
{
patch=I(cv::Rect(j,i,blockSide,blockSide));
cv::meanStdDev(patch,m,s);
if(s[0]>0.01) // Thresholding parameter (set smaller for lower contrast image)
{
Res.at<float>(i/blockSide,j/blockSide)=m[0];
}else
{
Res.at<float>(i/blockSide,j/blockSide)=0;
}
}
}
cv::resize(I,smallImg,Res.size());
cv::threshold(Res,inpaintmask,0.02,1.0,cv::THRESH_BINARY);
cv::Mat inpainted;
smallImg.convertTo(smallImg,CV_8UC1,255);
inpaintmask.convertTo(inpaintmask,CV_8UC1);
inpaint(smallImg, inpaintmask, inpainted, 5, cv::INPAINT_TELEA);
cv::resize(inpainted,Res,Img.size());
Res.convertTo(Res,CV_8UC3);
}
Although the inputted image is greyscaled, it outputs an yellowish image as shown below:
My hypothesis is that whilst conversion between the cv::Mat and UIImage, something happened leading to the color image, however I can not figure out how to fix this issue.
**please ignore the status bar as these images are screenshots of the iOS app.
Update:
I have tried using CV_8UC1 instead of CV_8UC3 for Res.convertTo() and added cvtColor(Res, Res, CV_GRAY2BGR); but am still getting very similar results.
Could it be the conversion between cv::mat and UIImage which is causing this problem??
I want my image to be like this shown below.
You can use OpenCV framework and implement below code
+(UIImage *)blackandWhite:(UIImage *)processedImage
{
cv::Mat original = [MMOpenCVHelper cvMatGrayFromAdjustedUIImage:processedImage];
cv::Mat new_image = cv::Mat::zeros( original.size(), original.type() );
original.convertTo(new_image, -1, 1.4, -50);
original.release();
UIImage *blackWhiteImage=[MMOpenCVHelper UIImageFromCVMat:new_image];
new_image.release();
return blackWhiteImage;
}
+ (cv::Mat)cvMatGrayFromAdjustedUIImage:(UIImage *)image
{
cv::Mat cvMat = [self cvMatFromAdjustedUIImage:image];
cv::Mat grayMat;
if ( cvMat.channels() == 1 ) {
grayMat = cvMat;
}
else {
grayMat = cv :: Mat( cvMat.rows,cvMat.cols, CV_8UC1 );
cv::cvtColor( cvMat, grayMat, cv::COLOR_BGR2GRAY );
}
return grayMat;
}
+ (cv::Mat)cvMatFromAdjustedUIImage:(UIImage *)image
{
CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage);
CGFloat cols = image.size.width;
CGFloat rows = image.size.height;
cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels
CGContextRef contextRef = CGBitmapContextCreate(cvMat.data, // Pointer to backing data
cols, // Width of bitmap
rows, // Height of bitmap
8, // Bits per component
cvMat.step[0], // Bytes per row
colorSpace, // Colorspace
kCGImageAlphaNoneSkipLast |
kCGBitmapByteOrderDefault);
CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage);
CGContextRelease(contextRef);
return cvMat;
}
+ (UIImage *)UIImageFromCVMat:(cv::Mat)cvMat
{
NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize() * cvMat.total()];
CGColorSpaceRef colorSpace;
if (cvMat.elemSize() == 1) {
colorSpace = CGColorSpaceCreateDeviceGray();
} else {
colorSpace = CGColorSpaceCreateDeviceRGB();
}
CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
CGImageRef imageRef = CGImageCreate(cvMat.cols, // Width
cvMat.rows, // Height
8, // Bits per component
8 * cvMat.elemSize(), // Bits per pixel
cvMat.step[0], // Bytes per row
colorSpace, // Colorspace
kCGImageAlphaNone | kCGBitmapByteOrderDefault, // Bitmap info flags
provider, // CGDataProviderRef
NULL, // Decode
false, // Should interpolate
kCGRenderingIntentDefault); // Intent
UIImage *image = [[UIImage alloc] initWithCGImage:imageRef];
CGImageRelease(imageRef);
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpace);
return image;
}
its working for me check the output for your document
Try this:
+ (UIImage *)processImageWithOpenCV:(UIImage*)inputImage {
cv::Mat cvImage = [inputImage CVMat];
threshold(cvImage, cvImage, 128, 255, cv::THRESH_BINARY);
return [UIImage imageWithCVMat:cvImage];
}
Result image:
I'm new to IOS developing but this problem i'm facing does not seem logical to me. I'm declaring a function in both ViewController.h and ViewController.mm (changed to.mm because i'm using C++) but when i call it in ViewController.mm i get use of undeclared identifier error.
Here's the declaration in the header file:
#import <UIKit/UIKit.h>
#import <opencv2/highgui/cap_ios.h>
using namespace cv;
#interface ViewController : UIViewController<CvVideoCameraDelegate>
{
IBOutlet UIImageView* imageview;
CvVideoCamera* videoCamera;
IBOutlet UILabel *label;
}
- (UIImage *) CVMatToImage:(cv::Mat) matrice;
#property (nonatomic, retain) CvVideoCamera* videoCamera;
-(IBAction)cameraStart:(id)sender;
-(IBAction)cameraStop:(id)sender;
#end
and the definition in the .mm file:
- (UIImage *) CVMatToImage:(cv::Mat) matrice
{
NSData *data = [NSData dataWithBytes:matrice.data length:matrice.elemSize()*matrice.total()];
CGColorSpaceRef colorSpace;
CGBitmapInfo bitmapInfo;
if (matrice.elemSize() == 1) {
colorSpace = CGColorSpaceCreateDeviceGray();
bitmapInfo = kCGImageAlphaNone | kCGBitmapByteOrderDefault;
} else {
colorSpace = CGColorSpaceCreateDeviceRGB();
bitmapInfo = kCGBitmapByteOrder32Little | (
matrice.elemSize() == 3? kCGImageAlphaNone : kCGImageAlphaNoneSkipFirst
);
}
CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
// Creating CGImage from cv::Mat
CGImageRef imageRef = CGImageCreate(
matrice.cols, //width
matrice.rows, //height
8, //bits per component
8 * matrice.elemSize(), //bits per pixel
matrice.step[0], //bytesPerRow
colorSpace, //colorspace
bitmapInfo, // bitmap info
provider, //CGDataProviderRef
NULL, //decode
false, //should interpolate
kCGRenderingIntentDefault //intent
);
// Getting UIImage from CGImage
UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpace);
return finalImage;
}
But when i call it inside an IBAction i get an error
-(IBAction)cameraStop:(id)sender
{
[self.videoCamera stop];
//////////////////////
// Don't forget to process image here
//////////////////////
UIImage *finalImageToOCR = CVMatToImage(cvMatrice);
[imageview setImage:finalImageToOCR];
G8Tesseract *tesseract = [[G8Tesseract alloc] initWithLanguage:#"fra"];
[tesseract setImage:finalImageToOCR];
[tesseract recognize];
NSLog(#"%#", [tesseract recognizedText]);
label.text = [NSString stringWithFormat:[tesseract recognizedText]];
}
You have defined an instance method and not a function. Like the other method calls in your code you need to use a method call along the lines of:
UIImage *finalImageToOCR = [<object instance> CVMatToImage:cvMatrice];
Alternatively if you want a function you would declare is as:
UIImage *CVMatToImage(cv::Mat matrice) { ... }
in which case the function cannot access any instance variables.
HTH
I am storing frames in real time from a CvVideoCamera using the - (void)processImage:(Mat&)image delegate method.
After storing the images I average them all into one image to replicate a long exposure shot using this code:
Mat merge(Vector<Mat> frames, double alpha)
{
Mat firstFrame = frames.front();
Mat exposed = firstFrame * alpha;
for (int i = 1; i < frames.size(); i++) {
Mat frame = frames[i];
exposed += frame * alpha;
}
return exposed;
}
After getting the averaged image back I convert it back to a UIImage, but the image I get back is in a strange color space, does anyone know how I can fix this?
Conversion code:
+ (UIImage *)UIImageFromCVMat:(cv::Mat)cvMat
{
NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize()*cvMat.total()];
CGColorSpaceRef colorSpace;
if ( cvMat.elemSize() == 1 ) {
colorSpace = CGColorSpaceCreateDeviceGray();
}
else {
colorSpace = CGColorSpaceCreateDeviceRGB();
}
CGDataProviderRef provider = CGDataProviderCreateWithCFData( (__bridge CFDataRef)data );
CGImageRef imageRef = CGImageCreate( cvMat.cols, cvMat.rows, 8, 8 * cvMat.elemSize(), cvMat.step[0], colorSpace, kCGImageAlphaNone|kCGBitmapByteOrderDefault, provider, NULL, false, kCGRenderingIntentDefault );
UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease( imageRef );
CGDataProviderRelease( provider );
CGColorSpaceRelease( colorSpace );
return finalImage;
}
Here is an example(note: the plane in the middle is because I am recording off a computer monitor)
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?
Found that I need to apply this code before converting to a UIImage
res.convertTo(res, CV_8UC3, 255.0);
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