Painter greyscale, image quality paint-brush!

[patrik08]

I am not the best paint-brush !

to make a color picture to greyscale i make so.

Is here a other mode to grab moore quality?

#include <QApplication>
#include <QtGui>
#include <QtCore> 
#include <QCoreApplication>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QLabel *label = new QLabel("Hello Picasso");
    QPixmap bw = QPixmap("test.png","",Qt::MonoOnly);
 
     QImage base0("test.png");
     QImage base =  base0.convertToFormat(QImage::Format_MonoLSB,Qt::MonoOnly);
     /////QPixmap display;
     QPixmap xnew(base.width(),base.height());
             xnew.fill();
 
                /* paint B/W */
                QPainter painter;
                painter.begin(&xnew); 
               ////// painter.setRenderHint(QPainter::Antialiasing);
                painter.drawImage(0,0,QImage("test.png"));
                painter.drawImage(base.width() / 2,0,base);
                painter.end();
 
    label->setPixmap(xnew);
    label->show();
    return app.exec();
}

#include <QApplication>
#include <QtGui>
#include <QtCore> 
#include <QCoreApplication>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QLabel *label = new QLabel("Hello Picasso");
    QPixmap bw = QPixmap("test.png","",Qt::MonoOnly);
    
     QImage base0("test.png");
     QImage base =  base0.convertToFormat(QImage::Format_MonoLSB,Qt::MonoOnly);
     /////QPixmap display;
     QPixmap xnew(base.width(),base.height());
             xnew.fill();
    
                /* paint B/W */
                QPainter painter;
                painter.begin(&xnew); 
               ////// painter.setRenderHint(QPainter::Antialiasing);
                painter.drawImage(0,0,QImage("test.png"));
                painter.drawImage(base.width() / 2,0,base);
                painter.end();
    
    label->setPixmap(xnew);
    label->show();
    return app.exec();
}

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[jacek]

Qt::MonoOnly and QImage::Format_MonoLSB are for black & white pictures (i.e. with exactly two colours), not grayscale ones.

[patrik08]

Qt::MonoOnly and QImage::Format_MonoLSB are for black & white pictures (i.e. with exactly two colours), not grayscale ones.

to build 256 level greyscale i must iterate each pixel?
or only so...
QImage base = base0.convertToFormat(QImage::Format_MonoLSB); ?

[jacek]

to build 256 level greyscale i must iterate each pixel?

If you had an image with a colour table, you would have to go only through the colour table.

or only so...
QImage base = base0.convertToFormat(QImage::Format_MonoLSB); ?

QImage::Format_MonoLSB isn't the best choice, as it uses only 1 bit per pixel. Better try QImage::Format_Indexed8 and convert the colour table using qGray().

[patrik08]

If QImage::Format_MonoLSB isn't the best choice, as it uses only 1 bit per pixel. Better try QImage::Format_Indexed8 and convert the colour table using qGray().

super i found on assistant Plug & Paint Basic Tools Example

tools/plugandpaintplugins/basictools/basictoolsplugin.h

the day will arrive that assistant speaks.

#include <QtGui>
#include <QtCore> 
#include <QCoreApplication>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QLabel *label = new QLabel("Hello Picasso");
    QPixmap bw = QPixmap("test.png");
 
     QImage base0("test.png");
     QImage base =  base0.convertToFormat(QImage::Format_RGB32);
 
      for (int y = 0; y < base.height(); ++y) {
             for (int x = 0; x < base.width(); ++x) {
                 int pixel = base.pixel(x, y);
                 int gray = qGray(pixel);
                 int alpha = qAlpha(pixel);
                 base.setPixel(x, y, qRgba(gray, gray, gray, alpha));
             }
         }
     QPixmap xnew(base.width(),base.height());
             xnew.fill();
 
                /* paint B/W */
                QPainter painter;
                painter.begin(&xnew); 
                painter.setRenderHint(QPainter::Antialiasing);
                painter.drawImage(0,0,QImage("test.png"));
                painter.drawImage(base.width() / 2,0,base);
                painter.end();
 
    label->setPixmap(xnew);
    label->show();
    return app.exec();
}

#include <QtGui>
#include <QtCore> 
#include <QCoreApplication>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QLabel *label = new QLabel("Hello Picasso");
    QPixmap bw = QPixmap("test.png");
    
     QImage base0("test.png");
     QImage base =  base0.convertToFormat(QImage::Format_RGB32);
    
      for (int y = 0; y < base.height(); ++y) {
             for (int x = 0; x < base.width(); ++x) {
                 int pixel = base.pixel(x, y);
                 int gray = qGray(pixel);
                 int alpha = qAlpha(pixel);
                 base.setPixel(x, y, qRgba(gray, gray, gray, alpha));
             }
         }
     QPixmap xnew(base.width(),base.height());
             xnew.fill();
    
                /* paint B/W */
                QPainter painter;
                painter.begin(&xnew); 
                painter.setRenderHint(QPainter::Antialiasing);
                painter.drawImage(0,0,QImage("test.png"));
                painter.drawImage(base.width() / 2,0,base);
                painter.end();
    
    label->setPixmap(xnew);
    label->show();
    return app.exec();
}

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