Artifacts around logo when used imagick compositeimage

[trangtv04110]

Line code: $top->compositeImage($logo, Imagick::COMPOSITE_OVER, $left_padding, $top_padding);

When I used composite method, it appear strange things around source image
Please see links:
http://screencast.com/t/8aBR7d9J
http://screencast.com/t/SmfaGfN3B

Help me !!!

[fmw42]

What version of Imagemagick and what version of Imagick are you using? Can you provide links to your two input images? You can upload them to dropbox.com (public folder) and put links here. What are your exact argument values? What are your input and output format? If jpeg, then you could be seeing compression artifacts?

[snibgo]

The white arrows are pointing to jpeg artifacts. Solution: don't use jpeg for images that have areas of flat colour.

[trangtv04110]

Thanks for your help.
I think it is because jpeg. If I used png, it not happens.
But I want to use jpeg, not png. Is there a solution here?

[snibgo]

"-quality 100" may reduce the problem.

Why do you want to use jpeg? It isn't designed for this type of image. A PNG is probably smaller than jpeg quality 100.