How to make a mask with QImage?

I want to make a mask image with QImage, I suppose the color of pixel (1, 1) is the brackground 's color and set that color to white, if the pixel's color(rgb) have big difference with the blackground's color then set the color to black.That's my code,but it doesn't work, when i set the mask, the picture doesnot show.

Code:

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QImage image;
bool tt = image.load(fileName, 0);
qDebug() << "Bool:" << tt;
QColor white(Qt::white);
QColor black(Qt::black);
 
int i =image.size().width();
int j =image.size().height();
 
QImage ConvertImage (i, j, QImage::Format_RGB32);
QColor maskColor = QColor::fromRgb (image.pixel(1, 1) );
 
int red = maskColor.red();
int green = maskColor.green();
int blue = maskColor.blue();
 
for(int x= 0; x<i; x++)
 {
     for(int y = 0; y<j; y++)
     {
         QColor color = QColor::fromRgb (image.pixel(x, y) );
 
         if((abs(red - color.red()) +
             abs(green - color.green()) +
             abs(blue - color.blue()))/3 <10 )
         {
             ConvertImage.setPixel(x, y, white.rgb()) ;
         }
         else
         {
             ConvertImage.setPixel(x, y, black.rgb()) ;
         }
     }
 }
QImage tmp = ConvertImage.convertToFormat(QImage::Format_Mono );
tmp.save("test", "png");

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PNG does not support bilevel (1 bit per pixel) images, but you are converting to a bilevel image before saving.

Try ConvertImage.save("test.png","png"); instead of the last 2 lines ?

Is QBitmap and QBitmap::fromImage() useful?

Quote:

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Originally Posted by koan

PNG does not support bilevel (1 bit per pixel) images, but you are converting to a bilevel image before saving.

Try ConvertImage.save("test.png","png"); instead of the last 2 lines ?

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Actually if i change the format ,for example, bmp, it also doesn't work.

Quote:

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Originally Posted by ChrisW67

Is QBitmap and QBitmap::fromImage() useful?

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I also have try this way, but it does not wrok

Code:

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bitImage = QBitmap::fromImage(ConvertImage);
    qDebug()<<bitImage.isQBitmap();                                        //print true
    ui.toolButton_2->setIcon(QPixmap::fromImage(image));
    ui.toolButton_2->setIconSize(QSize(32, 32));
    ui.toolButton_2->setMask( bitImage );
    ui.toolButton_2->setFixedSize(32, 32);

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This works fine for me:

Code:

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#include <QtGui>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    QImage image("source.png");
 
    QColor white(Qt::white);
    QColor black(Qt::black);
 
    QImage ConvertImage (image.width(), image.height(), QImage::Format_RGB32);
    QColor maskColor = QColor::fromRgb (image.pixel(1, 1) );
 
    int red = maskColor.red();
    int green = maskColor.green();
    int blue = maskColor.blue();
 
    for(int x= 0; x<image.width(); x++) {
        for(int y = 0; y<image.height(); y++) {
            QColor color = QColor::fromRgb (image.pixel(x, y) );
 
            if((abs(red - color.red()) +
                abs(green - color.green()) +
                abs(blue - color.blue()))/3 <10 ) {
                ConvertImage.setPixel(x, y, white.rgb()) ;
            }
            else {
                ConvertImage.setPixel(x, y, black.rgb()) ;
            }
        }
    }
    ConvertImage.save("mask.png", "png");
 
    QBitmap b = QBitmap::fromImage(ConvertImage, Qt::MonoOnly);
 
    QLabel l;
    l.setPixmap(QPixmap::fromImage(image));
    l.setMask(b);
    l.show();
    return app.exec();
}

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Yes, used the label the mask works fine, but with button, it doesnot work, How strange!