how to scale image?

**tiaoweiliao** · 9th March 2018, 02:06

I am currently doing imageViewer.

I have a problem , when i scale a image , i find QImage::scale so slow.

this leads UI thread block.

my image file size is 3MB and size is 8900*8105.

Do you have any good Suggestions?

thanks.

Qt Code:

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QTime time;
    time.start();
    QImage image(imagePath);
    qDebug()<<"load image time elapsed is : "<<time.elapsed();//load image time elapsed is :  4407
    image.scaled(image.width() * 0.09 , image.height() * 0.09 , Qt::KeepAspectRatio , Qt::SmoothTransformation);
    qDebug()<<"scaled image time elapsed is : "<<time.elapsed();//scaled image time elapsed is :  5231

QTime time;
    time.start();
    QImage image(imagePath);
    qDebug()<<"load image time elapsed is : "<<time.elapsed();//load image time elapsed is :  4407
    image.scaled(image.width() * 0.09 , image.height() * 0.09 , Qt::KeepAspectRatio , Qt::SmoothTransformation);
    qDebug()<<"scaled image time elapsed is : "<<time.elapsed();//scaled image time elapsed is :  5231

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