Qt open image from file - how to know image size

Question

I am getting image file with QFileDialog. Image can be in different standard image file extensions. How can I get image size (width and height)?

Answer 1

If you only need the size of the image, but not the image itself, it is better to use the QImageReader. As described in the wiki, not all image data is loaded. This procedure should be much faster:

QImageReader reader("image.png");
QSize sizeOfImage = reader.size();
int height = sizeOfImage.height();
int width = sizeOfImage.width();