Drawing off screen
There are a number of reasons why you might like to draw offscreen: you might want to compose a collection of images and show them one after another (this is called double-buffering, which you can do to avoid screen painting flicker when you draw onscreen), or write a program that generates image files directly.
As I mentioned in the previous section, Qt provides several classes for offscreen drawing, each with different advantages and disadvantages. These classes are QImage
, QPixmap
, QBitmap
, and QPicture
. Under normal circumstances, you need to choose between QImage
and QPixmap
.
Tip
QImage
is the class best-suited for general-purpose drawing where you're interested in loading the image from or saving the image to a file. If ...
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