What is the difference between QImage and QPixmap?

c++ qt qimage qpixmap
Mr.Tu picture Mr.Tu · Apr 25, 2012 · Viewed 35.1k times · Source

I do not understand what is the difference between QImage and QPixmap, they seem to offer the same functionality. When should I use a QImage and when should I use a QPixmap?

Answer

karlphillip picture karlphillip · Apr 25, 2012

Easilly answered by reading the docs on QImage and QPixmap:

The QPixmap class is an off-screen image representation that can be used as a paint device.

The QImage class provides a hardware-independent image representation that allows direct access to the pixel data, and can be used as a paint device.

Edit: Also, from @Dave's answer:

You can't manipulate a QPixmap outside the GUI-thread, but QImage has no such restriction.

And from @Arnold:

Here's a short summary that usually (not always) applies:

  • If you plan to manipulate an image, modify it, change pixels on it, etc., use a QImage.
  • If you plan to draw the same image more than once on the screen, convert it to a QPixmap.

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