convert PNG(alpha channel) format image to JPG, GIF, BMP

[Im Jinho]

Environment
- Visual Studio 2008
- Magick++

Hi, everyone.

I'm using work with Magick++.

When I convert PNG(alpha) format image to JPG format, the result image have rectangle blocks of black color along borderline of a picture.
I think it's rectangle block take effect by alpha channel value of png.

How to remove rectangle block of black color?

for more infomation, I want to show you a result image, but I don't know that how to upload a file.
sorry, and thanks.

[anthony]

JPEG does not allow alpha channel. You need to remove transparency from the image

Remove Alpha Transparency
http://www.imagemagick.org/Usage/basics/#alpha_remove