I was confusing Zbar::Image with Magick::Image.
Zbar::Image myZbarImage(width, height, format, raw, width*height);
is the constructor for Zbar::Image which is not directly compatible with Magick::Image, which has its on constructors manual. I can then easily display with the display()
function:
Magick::Image myMagickImage; // fill
myMagickImage.display();