When I do a `convert foo.png foo.jpg`, and foo.png is a partially transparent image, convert silently produces foo.jpg 100% opaque. convert should at least issue a warning that it is significantly altering the image when it does the conversion. Version-Release number of selected component (if applicable): ImageMagick-5.4.3.11-1
Please report this issue to the ImageMagick developers, if you feel it needs a warning.