[Qt-interest] Enhanced monochrome conversion

[M. Bashir Al-Noimi]

Hi All,

It's easy to convert any image to monochrome format by using 
QImage::convertToFormat like this:

pImage.convertToFormat(QImage::Format_Mono, Qt::MonoOnly|Qt::ThresholdDither|Qt::AvoidDither);

but convertToFormat always guessing that the value of conversion's 
threshold is 255 where in some cases we need to use another threshold's 
value. I checked out GIMP and I noticed that it uses an automatic method 
for guessing threshold's value (see the example below) so I'm wondering:

*How I can convert images to monochrome format by using auto threshold's 
value just like GIMP conversion method?*



Original


QImage conversion



Automatic GIMP conversion



*P.S*

I've wrote a stupid function for converting images to monochrome by 
using a specified threshold's value as following but I need to know how 
I can automatically specify threshold's value:

QImage getThresholdBW(QImage pImage, int threshold)
{
    QImage result = pImage;
    result.fill(255);
    for(int x=0; x<pImage.width(); x++)
        for(int y=0; y<pImage.height(); y++)
            result.setPixel(x, y, qGray(pImage.pixel(x, y))>threshold?qRgb(255, 255, 255):qRgb(0, 0, 0));

    return result;
}


-----

Best Regards
Muhammad Bashir Al-Noimi
My Blog: http://mbnoimi.net/

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