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();

Answer 2

从检索到的文件名创建一个 QPixmap 并调用QPixmap::size()