how to knoe the pixel value of a QImage or QPixmap

AlvaroS

hello everyone.
First of all thanks a lot for reading this post and being able to help.

I would like to sve an image with pixel values from a QImage.

My code looks like this:

            QImage img1(path_name_image); //Image creation //Ver como hacer con variable global.

            //Create matrix where each element will be a pixel value.
            matrix = new int *[img.width()];

            for(int i=0;i<img.width();++i)
                matrix[i] = new int [img.height()];

            for(int i=0;i<img.width();++i){
                for(int j=0;j<img.height();++j){
                    matrix[i][j] = QColor(img.pixel(i,j)).black() > 127 ? 0:1;
                    std::cout<<img1.pixel(i,j)<<std::endl;
                    std::cout<<matrix[i][j]<<std::endl;
                }
            }

But std::cout gives me values out of 0-256

I think the problem is that .pixel(i,j) returns the color of the pixel at coordinates (x, y), but coordinates of scene I think....

How can I get a matrix with pixel values right?

raven-worx

@AlvaroS
you receive values from 0-255 (QRgb) because it returns a 8-bit RGB values (quad-truplets).
If you want the specific color pass the returned value to QColor constructor or use qAlpha()/qRed()/qBlue()/... etc. on the value.

michelson

You can try using QImage::pixelColor()
http://doc.qt.io/qt-5/qimage.html#pixelColor

VRonin

@AlvaroS said:

My code looks like this:

            QImage img1(path_name_image); //Image creation //Ver como hacer con variable global.
                    matrix[i][j] = QColor(img.pixel(i,j)).black() > 127 ? 0:1;
                    std::cout<<img1.pixel(i,j)<<std::endl;

What is img? you declare only img1

currently cout will print the QRgb Value of the colour and matrix will contain 1 if the pixel "blackness" (black component of cmyk encoding) is less than 50% or 0 otherwise

@AlvaroS said:

I think the problem is that .pixel(i,j) returns the color of the pixel at coordinates (x, y), but coordinates of scene I think....

x and y are coordinates of the image (assuming img is a QImage)