QImage and Qt::transparent

[babu198649]

hi
i want to paint on an image.How to make the image background as transparent.

the following code can change the background color of the image .

QColormap colormap=QColormap::instance();
image.fill(colormap.pixel(Qt::green));

QColormap colormap=QColormap::instance();
image.fill(colormap.pixel(Qt::green));

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but it fails to make the background transparent even when the code is changed to

QColormap colormap=QColormap::instance();
image.fill(colormap.pixel(Qt::transparent));

QColormap colormap=QColormap::instance();
image.fill(colormap.pixel(Qt::transparent));

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i wnt to paint on aQImage rather than QPixmap is because, i am painting in a multithreaded program.

how to make the background of a QImage as transparent.